Update a configuration file

From Rosetta Code
Task
Update a configuration file
You are encouraged to solve this task according to the task description, using any language you may know.

We have a configuration file as follows:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
NEEDSPEELING

# This boolean is commented out
; SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 48

The task is to manipulate the configuration file as follows:

  • Disable the needspeeling option (using a semicolon prefix)
  • Enable the seedsremoved option by removing the semicolon and any leading whitespace
  • Change the numberofbananas parameter to 1024
  • Enable (or create if it does not exist in the file) a parameter for numberofstrawberries with a value of 62000


Note that configuration option names are not case sensitive. This means that changes should be effected, regardless of the case.

Options should always be disabled by prefixing them with a semicolon.

Lines beginning with hash symbols should not be manipulated and left unchanged in the revised file.

If a configuration option does not exist within the file (in either enabled or disabled form), it should be added during this update. Duplicate configuration option names in the file should be removed, leaving just the first entry.

For the purpose of this task, the revised file should contain appropriate entries, whether enabled or not for needspeeling,seedsremoved,numberofbananas and numberofstrawberries.)

The update should rewrite configuration option names in capital letters. However lines beginning with hashes and any parameter data must not be altered (eg the banana for favourite fruit must not become capitalized). The update process should also replace double semicolon prefixes with just a single semicolon (unless it is uncommenting the option, in which case it should remove all leading semicolons).

Any lines beginning with a semicolon or groups of semicolons, but no following option should be removed, as should any leading or trailing whitespace on the lines. Whitespace between the option and parameters should consist only of a single space, and any non-ASCII extended characters, tabs characters, or control codes (other than end of line markers), should also be removed.


Related tasks



AutoHotkey[edit]

; Author: AlephX, Aug 17 2011
data = %A_scriptdir%\rosettaconfig.txt
outdata = %A_scriptdir%\rosettaconfig.tmp
FileDelete, %outdata%
 
NUMBEROFBANANAS := 1024
numberofstrawberries := 560
NEEDSPEELING = "0"
FAVOURITEFRUIT := "bananas"
SEEDSREMOVED = "1"
BOOL0 = "0"
BOOL1 = "1"
NUMBER1 := 1
number0 := 0
STRINGA := "string here"
 
parameters = bool0|bool1|NUMBER1|number0|stringa|NEEDSPEELING|seedsremoved|numberofbananas|numberofstrawberries
 
Loop, Read, %data%, %outdata%
{
if (instr(A_LoopReadLine, "#") == 1 OR A_LoopReadLine == "")
{
Line := A_LoopReadLine
}
else
{
if instr(A_LoopReadLine, ";") == 1
{
parameter := RegExReplace(Substr(A_LoopReadLine,2), "^[ \s]+|[ \s]+$", "")
 
parametervalue = %parameter%
value := %parametervalue%
if value == 0
Line := A_loopReadLine
else
Line := Parameter
}
else
{
parameter := RegExReplace(A_LoopReadLine, "^[ \s]+|[ \s]+$", "")
if instr(parameter, A_Space)
parameter := substr(parameter, 1, instr(parameter, A_Space)-1)
 
if instr(parameters, parameter) > 0
{
parametervalue = %parameter%
value := %parametervalue%
 
if (value = chr(34) . "0" . chr(34))
Line := "; " . Parameter
else
{
if (value = chr(34) . "1" . chr(34))
Line := Parameter
else
Line = %parametervalue% %value%
}
}
else
Line := A_LoopReadLine
}
 
}
StringReplace, parameters, parameters, %parametervalue%,,
StringReplace, parameters, parameters,||,|
 
FileAppend, %Line%`n
}
 
Loop, parse, parameters,|
{
if (A_Loopfield <> "")
{
StringUpper, parameter, A_LoopField
parametervalue = %parameter%
value := %parametervalue%
 
if (value = chr(34) . "0" . chr(34))
Line := "; " . parameter
else
{
if (value = chr(34) . "1" . chr(34))
Line := parameter
else
Line = %parametervalue% %value%
}
 
FileAppend, %Line%`n, %outdata%
}
}
 
FileCopy, %A_scriptdir%\rosettaconfig.tmp, %A_scriptdir%\rosettaconfig.txt, 1

BASIC[edit]

Works with: QBasic version 1.1
Works with: QuickBasic version 4.5
Works with: VB-DOS version 1.0
Works with: QB64 version 1.1
Works with: PDS version 7.1

This program is not tied to the task requested, but it can read and modify ANY configuration file. It is somewhat long, but includes functionality to modify or add variables and values to the configuration file, append remarks (#) to it, read and save values in an array (comma separated), toggle comment mode for variables in a configuration file, etc. It is even longer because is almost fully commented and in key procedures every parameter is explained. It includes a main program cycle to read the configuration file and modify its values.

 
' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
' Read a Configuration File V1.0 '
' '
' Developed by A. David Garza Marín in VB-DOS for '
' RosettaCode. December 2, 2016. '
' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' ' '
 
' OPTION EXPLICIT ' For VB-DOS, PDS 7.1
' OPTION _EXPLICIT ' For QB64
 
' SUBs and FUNCTIONs
DECLARE SUB AppendCommentToConfFile (WhichFile AS STRING, WhichComment AS STRING, LeaveALine AS INTEGER)
DECLARE SUB setNValToVarArr (WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS DOUBLE)
DECLARE SUB setSValToVar (WhichVariable AS STRING, WhatValue AS STRING)
DECLARE SUB setSValToVarArr (WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS STRING)
DECLARE SUB doModifyArrValueFromConfFile (WhichFile AS STRING, WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS STRING, Separator AS STRING, ToComment AS INTEGER)
DECLARE SUB doModifyValueFromConfFile (WhichFile AS STRING, WhichVariable AS STRING, WhatValue AS STRING, Separator AS STRING, ToComment AS INTEGER)
DECLARE FUNCTION CreateConfFile% (WhichFile AS STRING)
DECLARE FUNCTION ErrorMessage$ (WhichError AS INTEGER)
DECLARE FUNCTION FileExists% (WhichFile AS STRING)
DECLARE FUNCTION FindVarPos% (WhichVariable AS STRING)
DECLARE FUNCTION FindVarPosArr% (WhichVariable AS STRING, WhichIndex AS INTEGER)
DECLARE FUNCTION getArrayVariable$ (WhichVariable AS STRING, WhichIndex AS INTEGER)
DECLARE FUNCTION getVariable$ (WhichVariable AS STRING)
DECLARE FUNCTION getVarType% (WhatValue AS STRING)
DECLARE FUNCTION GetDummyFile$ (WhichFile AS STRING)
DECLARE FUNCTION HowManyElementsInTheArray% (WhichVariable AS STRING)
DECLARE FUNCTION IsItAnArray% (WhichVariable AS STRING)
DECLARE FUNCTION IsItTheVariableImLookingFor% (TextToAnalyze AS STRING, WhichVariable AS STRING)
DECLARE FUNCTION NewValueForTheVariable$ (WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS STRING, Separator AS STRING)
DECLARE FUNCTION ReadConfFile% (NameOfConfFile AS STRING)
DECLARE FUNCTION YorN$ ()
 
' Register for values located
TYPE regVarValue
VarName AS STRING * 20
VarType AS INTEGER ' 1=String, 2=Integer, 3=Real, 4=Comment
VarValue AS STRING * 30
END TYPE
 
' Var
DIM rVarValue() AS regVarValue, iErr AS INTEGER, i AS INTEGER, iHMV AS INTEGER
DIM iArrayElements AS INTEGER, iWhichElement AS INTEGER, iCommentStat AS INTEGER
DIM iAnArray AS INTEGER, iSave AS INTEGER
DIM otherfamily(1 TO 2) AS STRING
DIM sVar AS STRING, sVal AS STRING, sComment AS STRING
CONST ConfFileName = "config2.fil"
CONST False = 0, True = NOT False
 
' ------------------- Main Program ------------------------
DO
CLS
ERASE rVarValue
PRINT "This program reads a configuration file and shows the result."
PRINT
PRINT "Default file name: "; ConfFileName
PRINT
iErr = ReadConfFile(ConfFileName)
IF iErr = 0 THEN
iHMV = UBOUND(rVarValue)
PRINT "Variables found in file:"
FOR i = 1 TO iHMV
PRINT RTRIM$(rVarValue(i).VarName); " = "; RTRIM$(rVarValue(i).VarValue); " (";
SELECT CASE rVarValue(i).VarType
CASE 0: PRINT "Undefined";
CASE 1: PRINT "String";
CASE 2: PRINT "Integer";
CASE 3: PRINT "Real";
CASE 4: PRINT "Is a commented variable";
END SELECT
PRINT ")"
NEXT i
PRINT
 
INPUT "Type the variable name to modify (Blank=End)"; sVar
sVar = RTRIM$(LTRIM$(sVar))
IF LEN(sVar) > 0 THEN
i = FindVarPos%(sVar)
IF i > 0 THEN ' Variable found
iAnArray = IsItAnArray%(sVar)
IF iAnArray THEN
iArrayElements = HowManyElementsInTheArray%(sVar)
PRINT "This is an array of"; iArrayElements; " elements."
INPUT "Which one do you want to modify (Default=1)"; iWhichElement
IF iWhichElement = 0 THEN iWhichElement = 1
ELSE
iArrayElements = 1
iWhichElement = 1
END IF
PRINT "The current value of the variable is: "
IF iAnArray THEN
PRINT sVar; "("; iWhichElement; ") = "; RTRIM$(rVarValue(i + (iWhichElement - 1)).VarValue)
ELSE
PRINT sVar; " = "; RTRIM$(rVarValue(i + (iWhichElement - 1)).VarValue)
END IF
ELSE
PRINT "The variable was not found. It will be added."
END IF
PRINT
INPUT "Please, set the new value for the variable (Blank=Unmodified)"; sVal
sVal = RTRIM$(LTRIM$(sVal))
IF i > 0 THEN
IF rVarValue(i + (iWhichElement - 1)).VarType = 4 THEN
PRINT "Do you want to remove the comment status to the variable? (Y/N)"
iCommentStat = NOT (YorN = "Y")
iCommentStat = ABS(iCommentStat) ' Gets 0 (Toggle) or 1 (Leave unmodified)
iSave = (iCommentStat = 0)
ELSE
PRINT "Do you want to toggle the variable as a comment? (Y/N)"
iCommentStat = (YorN = "Y") ' Gets 0 (Uncommented) or -1 (Toggle as a Comment)
iSave = iCommentStat
END IF
END IF
 
' Now, update or add the variable to the conf file
IF i > 0 THEN
IF sVal = "" THEN
sVal = RTRIM$(rVarValue(i).VarValue)
END IF
ELSE
PRINT "The variable will be added to the configuration file."
PRINT "Do you want to add a remark for it? (Y/N)"
IF YorN$ = "Y" THEN
LINE INPUT "Please, write your remark: ", sComment
sComment = LTRIM$(RTRIM$(sComment))
IF sComment <> "" THEN
AppendCommentToConfFile ConfFileName, sComment, True
END IF
END IF
END IF
 
' Verifies if the variable will be modified, and applies the modification
IF sVal <> "" OR iSave THEN
IF iWhichElement > 1 THEN
setSValToVarArr sVar, iWhichElement, sVal
doModifyArrValueFromConfFile ConfFileName, sVar, iWhichElement, sVal, " ", iCommentStat
ELSE
setSValToVar sVar, sVal
doModifyValueFromConfFile ConfFileName, sVar, sVal, " ", iCommentStat
END IF
END IF
 
END IF
ELSE
PRINT ErrorMessage$(iErr)
END IF
PRINT
PRINT "Do you want to add or modify another variable? (Y/N)"
LOOP UNTIL YorN$ = "N"
' --------- End of Main Program -----------------------
PRINT
PRINT "End of program."
END
 
FileError:
iErr = ERR
RESUME NEXT
 
SUB AppendCommentToConfFile (WhichFile AS STRING, WhichComment AS STRING, LeaveALine AS INTEGER)
' Parameters:
' WhichFile: Name of the file where a comment will be appended.
' WhichComment: A comment. It is suggested to add a comment no larger than 75 characters.
' This procedure adds a # at the beginning of the string if there is no #
' sign on it in order to ensure it will be added as a comment.
 
' Var
DIM iFil AS INTEGER
 
iFil = FileExists%(WhichFile)
IF NOT iFil THEN
iFil = CreateConfFile%(WhichFile) ' Here, iFil is used as dummy to save memory
END IF
 
IF iFil THEN ' Everything is Ok
iFil = FREEFILE ' Now, iFil is used to be the ID of the file
WhichComment = LTRIM$(RTRIM$(WhichComment))
 
IF LEFT$(WhichComment, 1) <> "#" THEN ' Is it in comment format?
WhichComment = "# " + WhichComment
END IF
 
' Append the comment to the file
OPEN WhichFile FOR APPEND AS #iFil
IF LeaveALine THEN
PRINT #iFil, ""
END IF
PRINT #iFil, WhichComment
CLOSE #iFil
END IF
 
END SUB
 
FUNCTION CreateConfFile% (WhichFile AS STRING)
' Var
DIM iFile AS INTEGER
 
ON ERROR GOTO FileError
 
iFile = FREEFILE
OPEN WhichFile FOR OUTPUT AS #iFile
CLOSE iFile
 
ON ERROR GOTO 0
 
CreateConfFile = FileExists%(WhichFile)
END FUNCTION
 
SUB doModifyArrValueFromConfFile (WhichFile AS STRING, WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS STRING, Separator AS STRING, ToComment AS INTEGER)
' Parameters:
' WhichFile: The name of the Configuration File. It can include the full path.
' WhichVariable: The name of the variable to be modified or added to the conf file.
' WhichIndex: The index number of the element to be modified in a matrix (Default=1)
' WhatValue: The new value to set in the variable specified in WhichVariable.
' Separator: The separator between the variable name and its value in the conf file. Defaults to a space " ".
' ToComment: A value to set or remove the comment mode of a variable: -1=Toggle to Comment, 0=Toggle to not comment, 1=Leave as it is.
 
' Var
DIM iFile AS INTEGER, iFile2 AS INTEGER, iError AS INTEGER
DIM iMod AS INTEGER, iIsComment AS INTEGER
DIM sLine AS STRING, sDummyFile AS STRING, sChar AS STRING
 
' If conf file doesn't exists, create one.
iError = 0
iMod = 0
IF NOT FileExists%(WhichFile) THEN
iError = CreateConfFile%(WhichFile)
END IF
 
IF NOT iError THEN ' File exists or it was created
Separator = RTRIM$(LTRIM$(Separator))
IF Separator = "" THEN
Separator = " " ' Defaults to Space
END IF
sDummyFile = GetDummyFile$(WhichFile)
 
' It is assumed a text file
iFile = FREEFILE
OPEN WhichFile FOR INPUT AS #iFile
 
iFile2 = FREEFILE
OPEN sDummyFile FOR OUTPUT AS #iFile2
 
' Goes through the file to find the variable
DO WHILE NOT EOF(iFile)
LINE INPUT #iFile, sLine
sLine = RTRIM$(LTRIM$(sLine))
sChar = LEFT$(sLine, 1)
iIsComment = (sChar = ";")
IF iIsComment THEN ' Variable is commented
sLine = LTRIM$(MID$(sLine, 2))
END IF
 
IF sChar <> "#" AND LEN(sLine) > 0 THEN ' Is not a comment?
IF IsItTheVariableImLookingFor%(sLine, WhichVariable) THEN
sLine = NewValueForTheVariable$(WhichVariable, WhichIndex, WhatValue, Separator)
iMod = True
IF ToComment = True THEN
sLine = "; " + sLine
END IF
ELSEIF iIsComment THEN
sLine = "; " + sLine
END IF
 
END IF
 
PRINT #iFile2, sLine
LOOP
 
' Reviews if a modification was done, if not, then it will
' add the variable to the file.
IF NOT iMod THEN
sLine = NewValueForTheVariable$(WhichVariable, 1, WhatValue, Separator)
PRINT #iFile2, sLine
END IF
CLOSE iFile2, iFile
 
' Removes the conf file and sets the dummy file as the conf file
KILL WhichFile
NAME sDummyFile AS WhichFile
END IF
 
END SUB
 
SUB doModifyValueFromConfFile (WhichFile AS STRING, WhichVariable AS STRING, WhatValue AS STRING, Separator AS STRING, ToComment AS INTEGER)
' To see details of parameters, please see doModifyArrValueFromConfFile
doModifyArrValueFromConfFile WhichFile, WhichVariable, 1, WhatValue, Separator, ToComment
END SUB
 
FUNCTION ErrorMessage$ (WhichError AS INTEGER)
' Var
DIM sError AS STRING
 
SELECT CASE WhichError
CASE 0: sError = "Everything went ok."
CASE 1: sError = "Configuration file doesn't exist."
CASE 2: sError = "There are no variables in the given file."
END SELECT
 
ErrorMessage$ = sError
END FUNCTION
 
FUNCTION FileExists% (WhichFile AS STRING)
' Var
DIM iFile AS INTEGER
DIM iItExists AS INTEGER
SHARED iErr AS INTEGER
 
ON ERROR GOTO FileError
iFile = FREEFILE
iErr = 0
OPEN WhichFile FOR BINARY AS #iFile
IF iErr = 0 THEN
iItExists = LOF(iFile) > 0
CLOSE #iFile
 
IF NOT iItExists THEN
KILL WhichFile
END IF
END IF
ON ERROR GOTO 0
FileExists% = iItExists
 
END FUNCTION
 
FUNCTION FindVarPos% (WhichVariable AS STRING)
' Will find the position of the variable
FindVarPos% = FindVarPosArr%(WhichVariable, 1)
END FUNCTION
 
FUNCTION FindVarPosArr% (WhichVariable AS STRING, WhichIndex AS INTEGER)
' Var
DIM i AS INTEGER, iHMV AS INTEGER, iCount AS INTEGER, iPos AS INTEGER
DIM sVar AS STRING, sVal AS STRING, sWV AS STRING
SHARED rVarValue() AS regVarValue
 
' Looks for a variable name and returns its position
iHMV = UBOUND(rVarValue)
sWV = UCASE$(LTRIM$(RTRIM$(WhichVariable)))
sVal = ""
iCount = 0
DO
i = i + 1
sVar = UCASE$(RTRIM$(rVarValue(i).VarName))
IF sVar = sWV THEN
iCount = iCount + 1
IF iCount = WhichIndex THEN
iPos = i
END IF
END IF
LOOP UNTIL i >= iHMV OR iPos > 0
 
FindVarPosArr% = iPos
END FUNCTION
 
FUNCTION getArrayVariable$ (WhichVariable AS STRING, WhichIndex AS INTEGER)
' Var
DIM i AS INTEGER
DIM sVal AS STRING
SHARED rVarValue() AS regVarValue
 
i = FindVarPosArr%(WhichVariable, WhichIndex)
sVal = ""
IF i > 0 THEN
sVal = RTRIM$(rVarValue(i).VarValue)
END IF
 
' Found it or not, it will return the result.
' If the result is "" then it didn't found the requested variable.
getArrayVariable$ = sVal
 
END FUNCTION
 
FUNCTION GetDummyFile$ (WhichFile AS STRING)
' Var
DIM i AS INTEGER, j AS INTEGER
 
' Gets the path specified in WhichFile
i = 1
DO
j = INSTR(i, WhichFile, "\")
IF j > 0 THEN i = j + 1
LOOP UNTIL j = 0
 
GetDummyFile$ = LEFT$(WhichFile, i - 1) + "$dummyf$.tmp"
END FUNCTION
 
FUNCTION getVariable$ (WhichVariable AS STRING)
' Var
DIM i AS INTEGER, iHMV AS INTEGER
DIM sVal AS STRING
 
' For a single variable, looks in the first (and only)
' element of the array that contains the name requested.
sVal = getArrayVariable$(WhichVariable, 1)
 
getVariable$ = sVal
END FUNCTION
 
FUNCTION getVarType% (WhatValue AS STRING)
' Var
DIM sValue AS STRING, dValue AS DOUBLE, iType AS INTEGER
 
sValue = RTRIM$(WhatValue)
iType = 0
IF LEN(sValue) > 0 THEN
IF ASC(LEFT$(sValue, 1)) < 48 OR ASC(LEFT$(sValue, 1)) > 57 THEN
iType = 1 ' String
ELSE
dValue = VAL(sValue)
IF CLNG(dValue) = dValue THEN
iType = 2 ' Integer
ELSE
iType = 3 ' Real
END IF
END IF
END IF
 
getVarType% = iType
END FUNCTION
 
FUNCTION HowManyElementsInTheArray% (WhichVariable AS STRING)
' Var
DIM i AS INTEGER, iHMV AS INTEGER, iCount AS INTEGER, iPos AS INTEGER, iQuit AS INTEGER
DIM sVar AS STRING, sVal AS STRING, sWV AS STRING
SHARED rVarValue() AS regVarValue
 
' Looks for a variable name and returns its value
iHMV = UBOUND(rVarValue)
sWV = UCASE$(LTRIM$(RTRIM$(WhichVariable)))
sVal = ""
 
' Look for all instances of WhichVariable in the
' list. This is because elements of an array will not alwasy
' be one after another, but alternate.
FOR i = 1 TO iHMV
sVar = UCASE$(RTRIM$(rVarValue(i).VarName))
IF sVar = sWV THEN
iCount = iCount + 1
END IF
NEXT i
 
HowManyElementsInTheArray = iCount
END FUNCTION
 
FUNCTION IsItAnArray% (WhichVariable AS STRING)
' Returns if a Variable is an Array
IsItAnArray% = (HowManyElementsInTheArray%(WhichVariable) > 1)
 
END FUNCTION
 
FUNCTION IsItTheVariableImLookingFor% (TextToAnalyze AS STRING, WhichVariable AS STRING)
' Var
DIM sVar AS STRING, sDT AS STRING, sDV AS STRING
DIM iSep AS INTEGER
 
sDT = UCASE$(RTRIM$(LTRIM$(TextToAnalyze)))
sDV = UCASE$(RTRIM$(LTRIM$(WhichVariable)))
iSep = INSTR(sDT, "=")
IF iSep = 0 THEN iSep = INSTR(sDT, " ")
IF iSep > 0 THEN
sVar = RTRIM$(LEFT$(sDT, iSep - 1))
ELSE
sVar = sDT
END IF
 
' It will return True or False
IsItTheVariableImLookingFor% = (sVar = sDV)
END FUNCTION
 
FUNCTION NewValueForTheVariable$ (WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS STRING, Separator AS STRING)
' Var
DIM iItem AS INTEGER, iItems AS INTEGER, iFirstItem AS INTEGER
DIM i AS INTEGER, iCount AS INTEGER, iHMV AS INTEGER
DIM sLine AS STRING, sVar AS STRING, sVar2 AS STRING
SHARED rVarValue() AS regVarValue
 
IF IsItAnArray%(WhichVariable) THEN
iItems = HowManyElementsInTheArray(WhichVariable)
iFirstItem = FindVarPosArr%(WhichVariable, 1)
ELSE
iItems = 1
iFirstItem = FindVarPos%(WhichVariable)
END IF
iItem = FindVarPosArr%(WhichVariable, WhichIndex)
sLine = ""
sVar = UCASE$(WhichVariable)
iHMV = UBOUND(rVarValue)
 
IF iItem > 0 THEN
i = iFirstItem
DO
sVar2 = UCASE$(RTRIM$(rVarValue(i).VarName))
 
IF sVar = sVar2 THEN ' Does it found an element of the array?
iCount = iCount + 1
IF LEN(sLine) > 0 THEN ' Add a comma
sLine = sLine + ", "
END IF
IF i = iItem THEN
sLine = sLine + WhatValue
ELSE
sLine = sLine + RTRIM$(rVarValue(i).VarValue)
END IF
END IF
i = i + 1
LOOP UNTIL i > iHMV OR iCount = iItems
 
sLine = WhichVariable + Separator + sLine
ELSE
sLine = WhichVariable + Separator + WhatValue
END IF
 
NewValueForTheVariable$ = sLine
END FUNCTION
 
FUNCTION ReadConfFile% (NameOfConfFile AS STRING)
' Var
DIM iFile AS INTEGER, iType AS INTEGER, iVar AS INTEGER, iHMV AS INTEGER
DIM iVal AS INTEGER, iCurVar AS INTEGER, i AS INTEGER, iErr AS INTEGER
DIM dValue AS DOUBLE, iIsComment AS INTEGER
DIM sLine AS STRING, sVar AS STRING, sValue AS STRING
SHARED rVarValue() AS regVarValue
 
' This procedure reads a configuration file with variables
' and values separated by the equal sign (=) or a space.
' It needs the FileExists% function.
' Lines begining with # or blank will be ignored.
IF FileExists%(NameOfConfFile) THEN
iFile = FREEFILE
REDIM rVarValue(1 TO 10) AS regVarValue
OPEN NameOfConfFile FOR INPUT AS #iFile
WHILE NOT EOF(iFile)
LINE INPUT #iFile, sLine
sLine = RTRIM$(LTRIM$(sLine))
IF LEN(sLine) > 0 THEN ' Does it have any content?
IF LEFT$(sLine, 1) <> "#" THEN ' Is not a comment?
iIsComment = (LEFT$(sLine, 1) = ";")
IF iIsComment THEN ' It is a commented variable
sLine = LTRIM$(MID$(sLine, 2))
END IF
iVar = INSTR(sLine, "=") ' Is there an equal sign?
IF iVar = 0 THEN iVar = INSTR(sLine, " ") ' if not then is there a space?
 
GOSUB AddASpaceForAVariable
iCurVar = iHMV
IF iVar > 0 THEN ' Is a variable and a value
rVarValue(iHMV).VarName = LEFT$(sLine, iVar - 1)
ELSE ' Is just a variable name
rVarValue(iHMV).VarName = sLine
rVarValue(iHMV).VarValue = ""
END IF
 
IF iVar > 0 THEN ' Get the value(s)
sLine = LTRIM$(MID$(sLine, iVar + 1))
DO ' Look for commas
iVal = INSTR(sLine, ",")
IF iVal > 0 THEN ' There is a comma
rVarValue(iHMV).VarValue = RTRIM$(LEFT$(sLine, iVal - 1))
GOSUB AddASpaceForAVariable
rVarValue(iHMV).VarName = rVarValue(iHMV - 1).VarName ' Repeats the variable name
sLine = LTRIM$(MID$(sLine, iVal + 1))
END IF
LOOP UNTIL iVal = 0
rVarValue(iHMV).VarValue = sLine
 
END IF
 
' Determine the variable type of each variable found in this step
FOR i = iCurVar TO iHMV
IF iIsComment THEN
rVarValue(i).VarType = 4 ' Is a comment
ELSE
GOSUB DetermineVariableType
END IF
NEXT i
 
END IF
END IF
WEND
CLOSE iFile
IF iHMV > 0 THEN
REDIM PRESERVE rVarValue(1 TO iHMV) AS regVarValue
iErr = 0 ' Everything ran ok.
ELSE
REDIM rVarValue(1 TO 1) AS regVarValue
iErr = 2 ' No variables found in configuration file
END IF
ELSE
iErr = 1 ' File doesn't exist
END IF
 
ReadConfFile = iErr
 
EXIT FUNCTION
 
AddASpaceForAVariable:
iHMV = iHMV + 1
 
IF UBOUND(rVarValue) < iHMV THEN ' Are there space for a new one?
REDIM PRESERVE rVarValue(1 TO iHMV + 9) AS regVarValue
END IF
RETURN
 
DetermineVariableType:
sValue = RTRIM$(rVarValue(i).VarValue)
IF LEN(sValue) > 0 THEN
IF ASC(LEFT$(sValue, 1)) < 48 OR ASC(LEFT$(sValue, 1)) > 57 THEN
rVarValue(i).VarType = 1 ' String
ELSE
dValue = VAL(sValue)
IF CLNG(dValue) = dValue THEN
rVarValue(i).VarType = 2 ' Integer
ELSE
rVarValue(i).VarType = 3 ' Real
END IF
END IF
END IF
RETURN
 
END FUNCTION
 
SUB setNValToVar (WhichVariable AS STRING, WhatValue AS DOUBLE)
' Sets a numeric value to a variable
setNValToVarArr WhichVariable, 1, WhatValue
END SUB
 
SUB setNValToVarArr (WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS DOUBLE)
' Sets a numeric value to a variable array
' Var
DIM sVal AS STRING
sVal = FORMAT$(WhatValue)
setSValToVarArr WhichVariable, WhichIndex, sVal
END SUB
 
SUB setSValToVar (WhichVariable AS STRING, WhatValue AS STRING)
' Sets a string value to a variable
setSValToVarArr WhichVariable, 1, WhatValue
END SUB
 
SUB setSValToVarArr (WhichVariable AS STRING, WhichIndex AS INTEGER, WhatValue AS STRING)
' Sets a string value to a variable array
' Var
DIM i AS INTEGER
DIM sVar AS STRING
SHARED rVarValue() AS regVarValue
 
i = FindVarPosArr%(WhichVariable, WhichIndex)
IF i = 0 THEN ' Should add the variable
IF UBOUND(rVarValue) > 0 THEN
sVar = RTRIM$(rVarValue(1).VarName)
IF sVar <> "" THEN
i = UBOUND(rVarValue) + 1
REDIM PRESERVE rVarValue(1 TO i) AS regVarValue
ELSE
i = 1
END IF
ELSE
REDIM rVarValue(1 TO i) AS regVarValue
END IF
rVarValue(i).VarName = WhichVariable
END IF
 
' Sets the new value to the variable
rVarValue(i).VarValue = WhatValue
rVarValue(i).VarType = getVarType%(WhatValue)
END SUB
 
FUNCTION YorN$ ()
' Var
DIM sYorN AS STRING
 
DO
sYorN = UCASE$(INPUT$(1))
IF INSTR("YN", sYorN) = 0 THEN
BEEP
END IF
LOOP UNTIL sYorN = "Y" OR sYorN = "N"
 
YorN$ = sYorN
END FUNCTION
 

In the following example, the user can modify the variables, their comment status and add the NUMBEROFSTRAWBERRIES variable with the value of 64000. In this case, the user is modifying the value of the NUMBEROFBANANAS variable in the configuration file.

This program reads a configuration file and shows the result.

Default file name: config.fil

Variables found in file:
FAVOURITEFRUIT = banana (String)
NEEDSPEELING = (Undefined)
SEEDSREMOVED = (Is a commented variable)
NUMBEROFBANANAS = 48 (Integer)

Type the variable name to modify (Blank=End)? numberofbananas
The current value of the variable is:
NUMBEROFBANANAS = 48

Please, set the new value for the variable (Blank=Unmodified)? 1024
Do you want to toggle the variable as a comment? (Y/N)

Do you want to add or modify another variable? (Y/N)

C[edit]

C with POSIX strcasecmp function for case-insensitive comparing. Substitute your toolchain's version.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
 
#define strcomp(X, Y) strcasecmp(X, Y)
 
struct option
{ const char *name, *value;
int flag; };
 
/* TODO: dynamically obtain these */
struct option updlist[] =
{ { "NEEDSPEELING", NULL },
{ "SEEDSREMOVED", "" },
{ "NUMBEROFBANANAS", "1024" },
{ "NUMBEROFSTRAWBERRIES", "62000" },
{ NULL, NULL } };
 
int output_opt(FILE *to, struct option *opt)
{ if (opt->value == NULL)
return fprintf(to, "; %s\n", opt->name);
else if (opt->value[0] == 0)
return fprintf(to, "%s\n", opt->name);
else
return fprintf(to, "%s %s\n", opt->name, opt->value); }
 
int update(FILE *from, FILE *to, struct option *updlist)
{ char line_buf[256], opt_name[128];
int i;
for (;;)
{ size_t len, space_span, span_to_hash;
if (fgets(line_buf, sizeof line_buf, from) == NULL)
break;
len = strlen(line_buf);
space_span = strspn(line_buf, "\t ");
span_to_hash = strcspn(line_buf, "#");
if (space_span == span_to_hash)
goto line_out;
if (space_span == len)
goto line_out;
if ((sscanf(line_buf, "; %127s", opt_name) == 1) ||
(sscanf(line_buf, "%127s", opt_name) == 1))
{ int flag = 0;
for (i = 0; updlist[i].name; i++)
{ if (strcomp(updlist[i].name, opt_name) == 0)
{ if (output_opt(to, &updlist[i]) < 0)
return -1;
updlist[i].flag = 1;
flag = 1; } }
if (flag == 0)
goto line_out; }
else
line_out:
if (fprintf(to, "%s", line_buf) < 0)
return -1;
continue; }
{ for (i = 0; updlist[i].name; i++)
{ if (!updlist[i].flag)
if (output_opt(to, &updlist[i]) < 0)
return -1; } }
return feof(from) ? 0 : -1; }
 
int main(void)
{ if (update(stdin, stdout, updlist) < 0)
{ fprintf(stderr, "failed\n");
return (EXIT_FAILURE); }
return 0; }

Run:

$ ./a.out  < configfile
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000

D[edit]

This type of file is really not very suitable for automated management, so this code is very basic.

import std.stdio, std.file, std.string, std.regex, std.path,
std.typecons;
 
final class Config {
enum EntryType { empty, enabled, disabled, comment, ignore }
 
static protected struct Entry {
EntryType type;
string name, value;
}
protected Entry[] entries;
protected string path;
 
this(in string path) {
if (!isValidPath(path) || (exists(path) && !isFile(path)))
throw new Exception("Invalid filename");
 
this.path = path;
if (!exists(path))
return;
 
auto r = regex(r"^(;*)\s*([A-Z0-9]+)\s*([A-Z0-9]*)", "i");
auto f = File(path, "r");
foreach (const buf; f.byLine()) {
auto line = buf.strip().idup;
if (!line.length)
entries ~= Entry(EntryType.empty);
else if (line[0] == '#')
entries ~= Entry(EntryType.comment, line);
else {
line = line.removechars("^a-zA-Z0-9\x20;");
auto m = match(line, r);
if (!m.empty && m.front[2].length) {
EntryType t = EntryType.enabled;
if (m.front[1].length)
t = EntryType.disabled;
addOption(m.front[2], m.front[3], t);
}
}
}
}
 
void enableOption(in string name) pure {
immutable i = getOptionIndex(name);
if (!i.isNull)
entries[i].type = EntryType.enabled;
}
 
void disableOption(in string name) pure {
immutable i = getOptionIndex(name);
if (!i.isNull)
entries[i].type = EntryType.disabled;
}
 
void setOption(in string name, in string value) pure {
immutable i = getOptionIndex(name);
if (!i.isNull)
entries[i].value = value;
}
 
void addOption(in string name, in string val,
in EntryType t = EntryType.enabled) pure {
entries ~= Entry(t, name.toUpper(), val);
}
 
void removeOption(in string name) pure {
immutable i = getOptionIndex(name);
if (!i.isNull)
entries[i].type = EntryType.ignore;
}
 
Nullable!size_t getOptionIndex(in string name) const pure {
foreach (immutable i, const ref e; entries) {
if (e.type != EntryType.enabled &&
e.type != EntryType.disabled)
continue;
if (e.name == name.toUpper())
return typeof(return)(i);
}
return typeof(return).init;
}
 
void store() {
auto f = File(path, "w+");
foreach (immutable e; entries) {
final switch (e.type) {
case EntryType.empty:
f.writeln();
break;
case EntryType.enabled:
f.writefln("%s %s", e.name, e.value);
break;
case EntryType.disabled:
f.writefln("; %s %s", e.name, e.value);
break;
case EntryType.comment:
f.writeln(e.name);
break;
case EntryType.ignore:
continue;
}
}
}
}
 
void main() {
auto cfg = new Config("config.txt");
cfg.enableOption("seedsremoved");
cfg.disableOption("needspeeling");
cfg.setOption("numberofbananas", "1024");
cfg.addOption("numberofstrawberries", "62000");
cfg.store();
}

Input file:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
    # be preserved.
 
# This is a favourite fruit
FAVOURITEFRUIT    ßßßßß		banana    µµµµ

# This is a boolean that should be set
NEEDspeeling

# This boolean is commented out
;;;; SEEDSREMOVED µµµµµ
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

# How many bananas we have
    NUMBEROFBANANAS µµµµµ 48

Output file:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING 

# This boolean is commented out
SEEDSREMOVED 

# How many bananas we have
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000

Erlang[edit]

Given the large number of very exact rules governing the update of this configuration file it is with some pleasure I add new options to the beginning of the file.

 
-module( update_configuration_file ).
 
-export( [add/3, change/3, disable/2, enable/2, read/1, task/0, write/2] ).
 
add( Option, Value, Lines ) ->
Upper = string:to_upper( Option ),
[string:join( [Upper, Value], " " ) | Lines].
 
change( Option, Value, Lines ) ->
Upper = string:to_upper( Option ),
change_done( Option, Value, Lines, [change_option(Upper, Value, X) || X <- Lines] ).
 
disable( Option, Lines ) ->
Upper = string:to_upper( Option ),
[disable_option(Upper, X) || X <- Lines].
 
enable( Option, Lines ) ->
Upper = string:to_upper( Option ),
[enable_option(Upper, X) || X <- Lines].
 
read( Name ) ->
{ok, Binary} = file:read_file( Name ),
Lines = [binary:bin_to_list(X) || X <- binary:split( Binary, <<"\n">>, [global] )],
Lines_no_white = [string:strip(X) || X <- Lines],
Lines_no_control = [strip_control(X) || X <- Lines_no_white],
Lines_no_consecutive_space = [string:join(string:tokens(X, " "), " ") || X <- Lines_no_control],
Lines_no_consecutive_semicolon = [strip_semicolon(X) || X <- Lines_no_consecutive_space],
Lines_no_empty = lists:filter( fun strip_empty/1, Lines_no_consecutive_semicolon ),
Lines_upper = [to_upper(X) || X <- Lines_no_empty],
lists:reverse( lists:foldl(fun remove_duplicates/2, [], Lines_upper) ).
 
task() ->
Lines = read( "priv/configuration_file2" ),
Disabled_lines = disable( "needspeeling", Lines ),
Enabled_lines = enable( "SEEDSREMOVED", Disabled_lines ),
Changed_lines1 = change( "NUMBEROFBANANAS", "1024", Enabled_lines ),
Changed_lines2 = change( "numberofstrawberries", "62000", Changed_lines1 ),
write( "configuration_file", Changed_lines2 ),
[io:fwrite( "Wrote this line: ~s~n", [X]) || X <- Changed_lines2].
 
write( Name, Lines ) -> file:write_file( Name, binary:list_to_bin(string:join(Lines, "\n")) ).
 
 
 
change_done( Option, Value, Lines, Lines ) -> add( Option, Value, Lines );
change_done( _Option, _Value, _Lines, New_lines ) -> New_lines.
 
change_option( Option, Value, String ) -> change_option_same( string:str(String, Option), Value, String ).
 
change_option_same( 1, Value, String ) ->
[Option | _T] = string:tokens( String, " " ),
string:join( [Option, Value], " " );
change_option_same( _N, _Value, String ) -> String.
 
disable_option( Option, String ) -> disable_option_same( string:str(String, Option), String ).
 
disable_option_same( 1, String ) -> "; " ++ String;
disable_option_same( _N, String ) -> String.
 
enable_option( Option, String ) -> enable_option_same( string:str(String, "; " ++ Option), String ).
 
enable_option_same( 1, "; " ++ String ) -> String;
enable_option_same( _N, String ) -> String.
 
is_semicolon( $; ) -> true;
is_semicolon( _C ) -> false.
 
remove_duplicates( "#" ++_T=Line, Lines ) -> [Line | Lines];
remove_duplicates( Line, Lines ) ->
Duplicates = [X || X <-Lines, 1 =:= string:str(Line, X)],
remove_duplicates( Duplicates, Line, Lines ).
 
remove_duplicates( [], Line, Lines ) -> [Line | Lines];
remove_duplicates( _Duplicates, _Line, Lines ) -> Lines.
 
strip_control( "" ) -> "";
strip_control( ";" ++ _T=String ) -> lists:filter( fun strip_control_codes:is_not_control_code_nor_extended_character/1, String );
strip_control( String ) -> String.
 
strip_empty( ";" ) -> false;
strip_empty( _String ) -> true.
 
 
strip_semicolon( ";" ++ _T=String ) -> ";" ++ lists:dropwhile( fun is_semicolon/1, String );
strip_semicolon( String ) -> String.
 
to_upper( "" ) -> "";
to_upper( "#" ++ _T=String ) -> String;
to_upper( "; " ++ _T=String ) ->
[";", Option | T] = string:tokens( String, " " ),
string:join( [";", string:to_upper(Option) | T], " " );
to_upper( String ) ->
[Option | T] = string:tokens( String, " " ),
string:join( [string:to_upper(Option) | T], " " ).
 
Output:
51> update_configuration_file:task().
Wrote this line: NUMBEROFSTRAWBERRIES 62000
Wrote this line: # This is a configuration file in standard configuration file format
Wrote this line: #
Wrote this line: # Lines begininning with a hash or a semicolon are ignored by the application
Wrote this line: # program. Blank lines are also ignored by the application program.
Wrote this line: 
Wrote this line: # The first word on each non comment line is the configuration option.
Wrote this line: # Remaining words or numbers on the line are configuration parameter
Wrote this line: # data fields.
Wrote this line: 
Wrote this line: # Note that configuration option names are not case sensitive. However,
Wrote this line: # configuration parameter data is case sensitive and the lettercase must
Wrote this line: # be preserved.
Wrote this line: 
Wrote this line: # This is a favourite fruit
Wrote this line: FAVOURITEFRUIT banana
Wrote this line: 
Wrote this line: # This is a boolean that should be set
Wrote this line: ; NEEDSPEELING
Wrote this line: 
Wrote this line: # This boolean is commented out
Wrote this line: SEEDSREMOVED
Wrote this line: 
Wrote this line: # How many bananas we have
Wrote this line: NUMBEROFBANANAS 1024

Fortran[edit]

Fortran has long had a built-in method for writing and reading a configuration file with ease, via the NAMELIST facility. The designers of the modern "configuration" files have paid not the slightest attention to the protocol, which is as follows:
      PROGRAM TEST	!Define some data aggregates, then write and read them.
CHARACTER*28 FAVOURITEFRUIT
LOGICAL NEEDSPEELING
LOGICAL SEEDSREMOVED
INTEGER NUMBEROFBANANAS
NAMELIST /FRUIT/ FAVOURITEFRUIT,NEEDSPEELING,SEEDSREMOVED,
1 NUMBEROFBANANAS
INTEGER F !An I/O unit number.
F = 10 !This will do.
 
Create an example file to show its format.
OPEN(F,FILE="Basket.txt",STATUS="REPLACE",ACTION="WRITE", !First, prepare a recipient file.
1 DELIM="QUOTE") !CHARACTER variables will be enquoted.
FAVOURITEFRUIT = "Banana"
NEEDSPEELING = .TRUE.
SEEDSREMOVED = .FALSE.
NUMBEROFBANANAS = 48
WRITE (F,FRUIT) !Write the lot in one go.
CLOSE (F) !Finished with output.
Can now read from the file.
OPEN(F,FILE="Basket.txt",STATUS="OLD",ACTION="READ", !Get it back.
1 DELIM="QUOTE")
READ (F,FRUIT) !Read who knows what.
WRITE (6,FRUIT)
END

Most of which is support stuff. The requirement is to declare a NAMELIST naming the variables of interest, then READ or WRITE using just the name of the NAMELIST. Only three statements, four if the file OPEN is counted.

One statement to write them

One statement to read them

One statement to find them all, and in the NAMELIST bind them.

(Apologies to J.R.R. Tolkien)

The result is a file in a standard layout.

 &FRUIT
 FAVOURITEFRUIT  = "Banana                      ",
 NEEDSPEELING    = T,
 SEEDSREMOVED    = F,
 NUMBEROFBANANAS =          48
 /

Evidently, the variables named in the NAMELIST are written out, one to a line in free-format with a style appropriate to its type, much as if they were assignment statements within a source file. Since Fortran compilers do not distinguish between upper and lower case, either may be used. The namelist's name starts the output, and the block of values ends with a line starting with a slash. On input, blocks will be skipped until the correct block name is found, so a single file may contain parameters for multiple usages. All output starts with column two so that column one can be used as a carriage control character if output is to go to a lineprinter. There is special provision for an array's value list whereby a run of equal values can be noted via n*value to save space, further, an input statement for an array can name a single element (the others being unaffected), and with F90, the usual array span facilities are available as in A(6:10) = 5*3.14 Should an output list of values be too long for the standard line length (133, again to suit lineprinters, but this value can be changed by RECL = n in the OPEN statement) then the list will be split across lines after a comma. However, long CHARACTER variables will cross multiple lines and column one will be used, something of a mistake should such output go to a lineprinter as it may react badly to strange carriage control characters.

Input allows for a comma-separated list of assignments and the names may appear in any order. If a name appears more than once, each assignment will be accepted so that the last one counts. Names can be omitted - if so, the corresponding variable will be unaffected by a READ. It would be nice if, the variable having been declared in CamelStyle, the name would be printed that way, but alas. F90 introduces the ! character as an "escape" comment and this is recognised in the NAMELIST input, outside of text literals of course.

To remove the SeedsRemoved entry is straightforward, depending on context. If its name is removed from the NAMELIST then it will no longer be written. The parameter file could of course be edited before being read back in, perhaps by a human, or by the installation process of the new version, or by the new version first finding the unwanted line, backspacing the file one record and writing the right number of spaces to wipe it without changing the length of a record - though this ploy may not be available if the filesystem provides limited support. If however a new version of the programme is expected to read the old version's parameter file, then there will be trouble because an unknown name (or an array index out of bounds, but not a CHARACTER variable being shorter than the supplied text) will provoke an I/O error and the run will crash. This can be avoided via the ERR = label option in the READ statement, however entries after the erroneous one will not be processed.

In a more general situation, it is helpful to have a routine that reads the NAMELIST style input and isolates the assignments so that each can individually be written to a scratch file in the NAMELIST style (i.e. providing the block head and tail lines, though some Fortrans allow NAMELIST input from a text variable and without this requirement) whereupon if ERR is provoked during the READ, the troublesome entry can be displayed for user appreciation before continuing with any remaining assignments.

Otherwise, the old NAMELIST could be used for input, with the undesired value simply ignored within the new version of the programme. For output, a new NAMELIST would be devised omitting the unwanted name - the same variables can be named in more than one NAMELIST. However, every NAMELIST's name must be unique within a routine and this would be the new block header name. So, read the parameter file in one routine which declares the old NAMELIST, complete with the name of the now unwanted variable, but write it via another routine which declares the new NAMELIST using the same name but omitting the names of undesired variables. The wanted variables would be in COMMON, or with F90 onwards be common names in a MODULE, or one could mess with parameter lists.
      MODULE MONKEYFODDER
INTEGER FIELD !An I/O unit number.
CHARACTER*28 FAVOURITEFRUIT
LOGICAL NEEDSPEELING
INTEGER NUMBEROFBANANAS
CONTAINS
SUBROUTINE GETVALS(FNAME) !Reads values from some file.
CHARACTER*(*) FNAME !The file name.
LOGICAL SEEDSREMOVED !This variable is no longer wanted.
NAMELIST /FRUIT/ FAVOURITEFRUIT,NEEDSPEELING,SEEDSREMOVED, !But still appears in this list.
1 NUMBEROFBANANAS
OPEN(FIELD,FILE=FNAME,STATUS="OLD",ACTION="READ", !Hopefully, the file exists.
1 DELIM="QUOTE") !Expect quoting for CHARACTER variables.
READ (FIELD,FRUIT,ERR = 666) !Read who knows what.
666 CLOSE (FIELD) !Ignoring any misformats.
END SUBROUTINE GETVALS !A proper routine would offer error messages.
 
SUBROUTINE PUTVALS(FNAME) !Writes values to some file.
CHARACTER*(*) FNAME !The file name.
NAMELIST /FRUIT/ FAVOURITEFRUIT,NEEDSPEELING,NUMBEROFBANANAS
OPEN(FIELD,FILE=FNAME,STATUS="REPLACE",ACTION="WRITE", !Prepare a recipient file.
1 DELIM="QUOTE") !CHARACTER variables will be enquoted.
WRITE (FIELD,FRUIT) !Write however much is needed.
CLOSE (FIELD) !Finished for now.
END SUBROUTINE PUTVALS
END MODULE MONKEYFODDER
 
PROGRAM TEST !Updates the file created by an earlier version.
USE MONKEYFODDER
FIELD = 10 !This will do.
CALL GETVALS("Basket.txt") !Read the values, allowing for the previous version.
CALL PUTVALS("Basket.txt") !Save the values, as per the new version.
END

Whereupon the file now has

 &FRUIT
 FAVOURITEFRUIT  = "Banana                      ",
 NEEDSPEELING    = T,
 NUMBEROFBANANAS =          48
 /

Naturally, a parameter file could contain data in whatever format was desired, and it might even employ a semicolon (of all things!) as a comment starter: such a file could be read and its components extracted via suitable code then written in the NAMELIST style to a scratch file and read back for the actual internalisation of values. The point of this is that a text name of a variable is associated with the actual computer variable via the NAMELIST facility, the programmer need not slog through some endless CASE statement on the names of the variables nor recognise the different data formats such as for complex numbers. This process would be reversed for output.

But given that the NAMELIST protocol is available without difficulty, why would a hard-core fortranner bother for a Fortran programme?

FreeBASIC[edit]

' FB 1.05.0 Win64
 
Type ConfigData
favouriteFruit As String
needsPeeling As Boolean
seedsRemoved As Boolean
numberOfBananas As UInteger
numberOfStrawberries As UInteger
End Type
 
Sub updateConfigData(fileName As String, cData As ConfigData)
Dim fileNum As Integer = FreeFile
Open fileName For Input As #fileNum
If err > 0 Then
Print "File could not be opened"
Sleep
End
End If
Dim tempFileName As String = "temp_" + fileName
Dim fileNum2 As Integer = FreeFile
Open tempFileName For Output As #fileNum2
Dim As Boolean hadFruit, hadPeeling, hadSeeds, hadBananas, hadStrawberries '' all false by default
Dim As String ln
While Not Eof(fileNum)
Line Input #fileNum, ln
If ln = "" OrElse Left(ln, 1) = "#" Then
Print #fileNum2, ln
Continue While
End If
ln = Trim(LTrim(ln, ";"), Any !" \t")
If ln = "" Then Continue While
If UCase(Left(ln, 14)) = "FAVOURITEFRUIT" Then
If hadFruit Then Continue While
hadFruit = True
Print #fileNum2, "FAVOURITEFRUIT " + cData.favouriteFruit
ElseIf UCase(Left(ln, 12)) = "NEEDSPEELING" Then
If hadPeeling Then Continue While
hadPeeling = True
If cData.needsPeeling Then
Print #fileNum2, "NEEDSPEELING"
Else
Print #fileNum2, "; NEEDSPEELING"
End If
ElseIf UCase(Left(ln, 12)) = "SEEDSREMOVED" Then
If hadSeeds Then Continue While
hadSeeds = True
If cData.seedsRemoved Then
Print #fileNum2, "SEEDSREMOVED"
Else
Print #fileNum2, "; SEEDSREMOVED"
End If
ElseIf UCase(Left(ln, 15)) = "NUMBEROFBANANAS" Then
If hadBananas Then Continue While
hadBananas = True
Print #fileNum2, "NUMBEROFBANANAS " + Str(cData.numberOfBananas)
ElseIf UCase(Left(ln, 20)) = "NUMBEROFSTRAWBERRIES" Then
If hadStrawberries Then Continue While
hadStrawberries = True
Print #fileNum2, "NUMBEROFSTRAWBERRIES " + Str(cData.numberOfStrawBerries)
End If
Wend
 
If Not hadFruit Then
Print #fileNum2, "FAVOURITEFRUIT " + cData.favouriteFruit
End If
If Not hadPeeling Then
If cData.needsPeeling Then
Print #fileNum2, "NEEDSPEELING"
Else
Print #fileNum2, "; NEEDSPEELING"
End If
End If
If Not hadSeeds Then
If cData.seedsRemoved Then
Print #fileNum2, "SEEDSREMOVED"
Else
Print #fileNum2, "; SEEDSREMOVED"
End If
End If
If Not hadBananas Then
Print #fileNum2, "NUMBEROFBANANAS " + Str(cData.numberOfBananas)
End If
If Not hadStrawberries Then
Print #fileNum2, "NUMBEROFSTRAWBERRIES " + Str(cData.numberOfStrawBerries)
End If
 
Close #fileNum : Close #fileNum2
Kill(fileName)
Name (tempFileName fileName)
End Sub
 
Dim fileName As String = "config2.txt"
Dim cData As ConfigData
With cData
.favouriteFruit = "banana"
.needsPeeling = False
.seedsRemoved = True
.numberOfBananas = 1024
.numberOfStrawberries = 62000
End With
 
updateConfigData fileName, cData
Print
Print "Press any key to quit"
Sleep

The contents of config2.txt after updating are:

Output:
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000

Go[edit]

package main
 
import (
"bufio"
"fmt"
"io"
"log"
"os"
"strings"
"unicode"
)
 
// line represents a single line in the configuration file.
type line struct {
kind lineKind
option string
value string
disabled bool
}
 
// lineKind represents the different kinds of configuration line.
type lineKind int
 
const (
_ lineKind = iota
ignore
parseError
comment
blank
value
)
 
func (l line) String() string {
switch l.kind {
case ignore, parseError, comment, blank:
return l.value
case value:
s := l.option
if l.disabled {
s = "; " + s
}
if l.value != "" {
s += " " + l.value
}
return s
}
panic("unexpected line kind")
}
 
func removeDross(s string) string {
return strings.Map(func(r rune) rune {
if r < 32 || r > 0x7f || unicode.IsControl(r) {
return -1
}
return r
}, s)
}
 
func parseLine(s string) line {
if s == "" {
return line{kind: blank}
}
if s[0] == '#' {
return line{kind: comment, value: s}
}
s = removeDross(s)
fields := strings.Fields(s)
if len(fields) == 0 {
return line{kind: blank}
}
// Strip leading semicolons (but record that we found them)
semi := false
for len(fields[0]) > 0 && fields[0][0] == ';' {
semi = true
fields[0] = fields[0][1:]
}
// Lose the first field if it was all semicolons
if fields[0] == "" {
fields = fields[1:]
}
switch len(fields) {
case 0:
// This can only happen if the line starts
// with a semicolon but has no other information
return line{kind: ignore}
case 1:
return line{
kind: value,
option: strings.ToUpper(fields[0]),
disabled: semi,
}
case 2:
return line{
kind: value,
option: strings.ToUpper(fields[0]),
value: fields[1],
disabled: semi,
}
}
return line{kind: parseError, value: s}
}
 
// Config represents a "standard" configuration file.
type Config struct {
options map[string]int // index of each option in lines.
lines []line
}
 
// index returns the index of the given option in
// c.lines, or -1 if not found.
func (c *Config) index(option string) int {
if i, ok := c.options[option]; ok {
return i
}
return -1
}
 
// addLine adds a line to the config, ignoring
// duplicate options and "ignore" lines.
func (c *Config) addLine(l line) {
switch l.kind {
case ignore:
return
case value:
if c.index(l.option) >= 0 {
return
}
c.options[l.option] = len(c.lines)
c.lines = append(c.lines, l)
default:
c.lines = append(c.lines, l)
}
}
 
// ReadConfig reads a configuration file from path and returns it.
func ReadConfig(path string) (*Config, error) {
f, err := os.Open(path)
if err != nil {
return nil, err
}
defer f.Close()
r := bufio.NewReader(f)
c := &Config{options: make(map[string]int)}
for {
s, err := r.ReadString('\n')
if s != "" {
if err == nil {
// strip newline unless we encountered an error without finding one.
s = s[:len(s)-1]
}
c.addLine(parseLine(s))
}
if err == io.EOF {
break
}
if err != nil {
return nil, err
}
}
return c, nil
}
 
// Set sets an option to a value, adding the option if necessary. If
// the option was previously disabled, it will be enabled.
func (c *Config) Set(option string, val string) {
if i := c.index(option); i >= 0 {
line := &c.lines[i]
line.disabled = false
line.value = val
return
}
c.addLine(line{
kind: value,
option: option,
value: val,
})
}
 
// Enable sets the enabled status of an option. It is
// ignored if the option does not already exist.
func (c *Config) Enable(option string, enabled bool) {
if i := c.index(option); i >= 0 {
c.lines[i].disabled = !enabled
}
}
 
// Write writes the configuration file to the writer.
func (c *Config) Write(w io.Writer) {
for _, line := range c.lines {
fmt.Println(line)
}
}
 
func main() {
c, err := ReadConfig("/tmp/cfg")
if err != nil {
log.Fatalln(err)
}
c.Enable("NEEDSPEELING", false)
c.Set("SEEDSREMOVED", "")
c.Set("NUMBEROFBANANAS", "1024")
c.Set("NUMBEROFSTRAWBERRIES", "62000")
c.Write(os.Stdout)
}

Haskell[edit]

Necessary imports

import Data.Char (toUpper)
import qualified System.IO.Strict as S

Definition of datatypes:

data INI = INI { entries :: [Entry] } deriving Show
 
data Entry = Comment String
| Field String String
| Flag String Bool
| EmptyLine
 
instance Show Entry where
show entry = case entry of
Comment text -> "# " ++ text
Field f v -> f ++ " " ++ v
Flag f True -> f
Flag f False -> "; " ++ f
EmptyLine -> ""
 
instance Read Entry where
readsPrec _ s = [(interprete (clean " " s), "")]
where
clean chs = dropWhile (`elem` chs)
interprete ('#' : text) = Comment text
interprete (';' : f)= flag (clean " ;" f) False
interprete entry = case words entry of
[] -> EmptyLine
[f] -> flag f True
f : v -> field f (unwords v)
field f = Field (toUpper <$> f)
flag f = Flag (toUpper <$> f)

Getting and setting fields in INI data:

setValue :: String -> String -> INI -> INI
setValue f v = INI . replaceOn (eqv f) (Field f v) . entries
 
setFlag :: String -> Bool -> INI -> INI
setFlag f v = INI . replaceOn (eqv f) (Flag f v) . entries
 
enable f = setFlag f True
disable f = setFlag f False
 
eqv f entry = (toUpper <$> f) == (toUpper <$> field entry)
where field (Field f _) = f
field (Flag f _) = f
field _ = ""
 
replaceOn p x lst = prev ++ x : post
where
(prev,post) = case break p lst of
(lst, []) -> (lst, [])
(lst, _:xs) -> (lst, xs)

IO stuff:

readIni :: String -> IO INI
readIni file = INI . map read . lines <$> S.readFile file
 
writeIni :: String -> INI -> IO ()
writeIni file = writeFile file . unlines . map show . entries
 
updateIni :: String -> (INI -> INI) -> IO ()
updateIni file f = readIni file >>= writeIni file . f
 
main = updateIni "test.ini" $
disable "NeedsPeeling" .
enable "SeedsRemoved" .
setValue "NumberOfBananas" "1024" .
setValue "NumberOfStrawberries" "62000"

J[edit]

Since the task does not specify the line end character, we assume that the last character in the file is the line end character.

require 'regex strings'
 
normalize=:3 :0
seen=. a:
eol=. {:;y
t=. ''
for_line.<;._2;y do. lin=. deb line=.>line
if. '#'={.line do. t=.t,line,eol
elseif. ''-:lin do. t =. t,eol
elseif. do.
line=. 1 u:([-.-.)&(32+i.95)&.(3&u:) line
base=. ('^ *;;* *';'') rxrplc line
nm=. ;name=. {.;:toupper base
if. -. name e. seen do.
seen=. seen, name
t=. t,eol,~dtb ('; '#~';'={.lin),(('^(?i) *',nm,'\b *');(nm,' ')) rxrplc base
end.
end.
end.t
)
 
enable=:1 :0
(<m) 1!:2~ normalize (,y,{:);<@rxrplc~&(y;~'^; *(?i)',y,'\b');.2]1!:1<m
)
 
disable=:1 :0
(<m) 1!:2~ normalize (,'; ',y,{:);<@rxrplc~&(('; ',y);~'^ *(?i)',y,'\b');.2]1!:1<m
)
 
set=:1 :0
:
t=. 1!:1<m
pat=. '^ *(?i)',y,'\b.*'
upd=. y,' ',":x
(<m) 1!:2~ normalize (,upd,{:);<@rxrplc~&(pat;upd) t
)

Note that, aside from the line end issue, the task is ambiguous because it specifies a set of operations rather than a file format. If the consequences of these ambiguities are troubling, you might prefer to replace normalize with normalize^:_

Example use:

   'example.file' disable 'needspeeling'
'example.file' enable 'seedsremoved'
1024 'example.file' set 'numberofbananas'
62000 'example.file' set 'numberofstrawberries'

Here's how the file specified in the task description looks after these steps have been executed:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024

NUMBEROFSTRAWBERRIES 62000

Java[edit]

Translation of: D
Works with: Java version 7
import java.io.*;
import java.util.*;
import java.util.regex.*;
 
public class UpdateConfig {
 
public static void main(String[] args) {
if (args[0] == null) {
System.out.println("filename required");
 
} else if (readConfig(args[0])) {
enableOption("seedsremoved");
disableOption("needspeeling");
setOption("numberofbananas", "1024");
addOption("numberofstrawberries", "62000");
store();
}
}
 
private enum EntryType {
EMPTY, ENABLED, DISABLED, COMMENT
}
 
private static class Entry {
EntryType type;
String name, value;
 
Entry(EntryType t, String n, String v) {
type = t;
name = n;
value = v;
}
}
 
private static Map<String, Entry> entries = new LinkedHashMap<>();
private static String path;
 
private static boolean readConfig(String p) {
path = p;
 
File f = new File(path);
if (!f.exists() || f.isDirectory())
return false;
 
String regexString = "^(;*)\\s*([A-Za-z0-9]+)\\s*([A-Za-z0-9]*)";
Pattern regex = Pattern.compile(regexString);
 
try (Scanner sc = new Scanner(new FileReader(f))){
int emptyLines = 0;
String line;
while (sc.hasNext()) {
line = sc.nextLine().trim();
 
if (line.isEmpty()) {
addOption("" + emptyLines++, null, EntryType.EMPTY);
 
} else if (line.charAt(0) == '#') {
entries.put(line, new Entry(EntryType.COMMENT, line, null));
 
} else {
line = line.replaceAll("[^a-zA-Z0-9\\x20;]", "");
Matcher m = regex.matcher(line);
 
if (m.find() && !m.group(2).isEmpty()) {
 
EntryType t = EntryType.ENABLED;
if (!m.group(1).isEmpty())
t = EntryType.DISABLED;
 
addOption(m.group(2), m.group(3), t);
}
}
}
} catch (IOException e) {
System.out.println(e);
}
return true;
}
 
private static void addOption(String name, String value) {
addOption(name, value, EntryType.ENABLED);
}
 
private static void addOption(String name, String value, EntryType t) {
name = name.toUpperCase();
entries.put(name, new Entry(t, name, value));
}
 
private static void enableOption(String name) {
Entry e = entries.get(name.toUpperCase());
if (e != null)
e.type = EntryType.ENABLED;
}
 
private static void disableOption(String name) {
Entry e = entries.get(name.toUpperCase());
if (e != null)
e.type = EntryType.DISABLED;
}
 
private static void setOption(String name, String value) {
Entry e = entries.get(name.toUpperCase());
if (e != null)
e.value = value;
}
 
private static void store() {
try (PrintWriter pw = new PrintWriter(path)) {
for (Entry e : entries.values()) {
switch (e.type) {
case EMPTY:
pw.println();
break;
case ENABLED:
pw.format("%s %s%n", e.name, e.value);
break;
case DISABLED:
pw.format("; %s %s%n", e.name, e.value);
break;
case COMMENT:
pw.println(e.name);
break;
default:
break;
}
}
if (pw.checkError()) {
throw new IOException("writing to file failed");
}
} catch (IOException e) {
System.out.println(e);
}
}
}

Input file:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
    # be preserved.

# This is a favourite fruit
FAVOURITEFRUIT    ßßßßß		banana    µµµµ

# This is a boolean that should be set
NEEDspeeling

# This boolean is commented out
;;;; SEEDSREMOVED µµµµµ
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

# How many bananas we have
    NUMBEROFBANANAS µµµµµ 48

Output:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING 

# This boolean is commented out
SEEDSREMOVED 

# How many bananas we have
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000

Lasso[edit]

Config type definition

#!/usr/bin/lasso9
 
define config => type {
 
data public configtxt, public path
 
public oncreate(
path::string = 'testing/configuration.txt'
) => {
.configtxt = file(#path) -> readstring
.path = #path
}
 
public get(term::string) => {
.clean
local(
regexp = regexp(-find = `(?m)^` + #term + `($|\s*=\s*|\s+)(.*)$`, -input = .configtxt, -ignorecase),
result
)
 
while(#regexp -> find) => {
#result = (#regexp -> groupcount > 1 ? (#regexp -> matchString(2) -> trim& || true))
if(#result -> asstring >> ',') => {
#result = #result -> split(',')
#result -> foreach => {#1 -> trim}
}
return #result
}
return false
}
 
public set(term::string, value) => {
if(#value === false) => {
.disable(#term)
return
}
.enable(#term)
if(#value -> isanyof(::string, ::integer, ::decimal)) => {
.configtxt = regexp(-find = `(?m)^(` + #term + `) ?(.*?)$`, -replace = `$1 ` + #value, -input = .configtxt, -ignorecase) -> replaceall
}
}
 
public disable(term::string) => {
.clean
local(regexp = regexp(-find = `(?m)^(` + #term + `)`, -replace = `; $1`, -input = .configtxt, -ignorecase))
.configtxt = #regexp -> replaceall
}
 
public enable(term::string, -comment::string = '# Added ' + date) => {
.clean
local(regexp = regexp(-find = `(?m)^(; )?(` + #term + `)`, -replace = `$2`, -input = .configtxt, -ignorecase))
if(#regexp -> find) => {
.configtxt = #regexp -> replaceall
else
.configtxt -> append('\n' + (not #comment -> beginswith('#') ? '# ') +
#comment + '\n' +
string_uppercase(#term) + '\n'
)
}
}
 
public write => {
local(config = file(.path))
#config -> opentruncate
#config -> dowithclose => {
#config -> writestring(.configtxt)
}
 
}
 
public clean => {
 
local(
cleaned = array,
regexp = regexp(-find = `^(;+)\W*$`)
)
 
with line in .configtxt -> split('\n') do {
#line -> trim
#regexp -> input = #line
 
if(#line -> beginswith('#') or #line == '') => {
#cleaned -> insert(#line)
else(not (#regexp -> find))
if(#line -> beginswith(';')) => {
#line -> replace(regexp(`^;+ *`), `; `)
else
#line -> replace(regexp(`^(.*?) +(.*?)`), `$1 $2`)
}
#line -> replace(regexp(`\t`))
#cleaned -> insert(#line)
}
}
 
.configtxt = #cleaned -> join('\n')
 
}
 
}

How to call it:

 
local(
config = config,
)
 
stdoutnl(#config -> get('FAVOURITEFRUIT'))
stdoutnl(#config -> get('SEEDSREMOVED'))
stdoutnl(#config -> get('NUMBEROFBANANAS'))
 
#config -> enable('seedsremoved')
#config -> enable('PARAMWITHCOMMENT', -comment = 'This param was added to demonstrate the possibility to also have comments associated with it')
#config -> disable('needspeeling')
#config -> set('numberofstrawberries', 62000)
#config -> set('numberofbananas', 1024)
 
#config -> write

Initial config file:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

 # This is a favourite fruit
FAVOURITEFRUIT   banana

# This is a boolean that should be set
 NEEDSPEELING

# This boolean is commented out
 ;  SEEDSREMOVED  

# This boolean is commented out
 ;  HEEDSREMOVED

# Another option 
;; OOPS Remove 	the double ;
;
;; 
  
# How many bananas we have
NUMBEROFBANANAS 48  

Final config file:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# This boolean is commented out
; HEEDSREMOVED

# Another option
; OOPS Remove the double ;

# How many bananas we have
NUMBEROFBANANAS 1024

# This param was added to demonstrate the possibility to also have comments associated with it
PARAMWITHCOMMENT

# Added 2013-12-01 00:32:00
NUMBEROFSTRAWBERRIES 62000

Perl[edit]

use warnings;
use strict;
 
my $needspeeling = 0;
my $seedsremoved = 1;
my $numberofstrawberries = 62000;
my $numberofbananas = 1024;
my $favouritefruit = 'bananas';
 
my @out;
 
sub config {
my (@config) = <DATA>;
push @config, "NUMBEROFSTRAWBERRIES $numberofstrawberries\n"
unless grep { /^;*[ \t]*NUMBEROFSTRAWBERRIES\b/; } @config;
 
foreach my $line (@config) {
 
if (substr($line, 0, 1) eq '#') {
push @out, $line;
next;
}
 
next if $line =~ /^[;\t ]+$/;
 
my ($option, $option_name);
 
if ($line =~ /^([A-Z]+[0-9]*)/) {
$option_name = lc $1;
$option = eval "\\\$$option_name";
my $value = eval "\${$option_name}";
 
if ($value) {
$$option = $value;
}
else {
$line = '; ' . $line;
$$option = undef;
}
}
elsif ($line =~ /^;+\s*([A-Z]+[0-9]*)/) {
$option_name = lc $1;
$option = eval "\\\$$option_name";
my $value = eval "\${$option_name}";
 
if ($value) {
$line =~ s/^;+\s*//;
$$option = $value == 1 ? '' : $value;
}
else {
$$option = undef;
}
}
 
if (defined $$option) {
push @out, "\U$option_name\E $$option\n"
unless grep { /^\U$option_name\E\b/; } @out;
}
else {
$line =~ s/\s*[^[:ascii:]]+\s*$//;
$line =~ s/[[:cntrl:]\s]+$//;
push(@out, "$line\n");
}
}
}
 
config();
 
my $file = join('', @out);
$file =~ s/\n{3,}/\n\n/g;
 
print $file;
 
__DATA__
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.
 
# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.
 
# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.
 
# This is a favourite fruit
FAVOURITEFRUIT banana
 
# This is a boolean that should be set
NEEDSPEELING
 
# This boolean is commented out
; SEEDSREMOVED
 
# How many bananas we have
NUMBEROFBANANAS 48

Perl 6[edit]

Implemented as a command-line script which can make arbitrary in-place updates to such config files.

Assuming that the script is saved as conf-update and the config file as test.cfg, the four changes required by the task description could be performed with the command:

conf-update --/needspeeling --seedsremoved --numberofbananas=1024 --numberofstrawberries=62000 test.cfg

The script:

#!/usr/bin/env perl6
 
my $tmpfile = tmpfile;
 
sub MAIN ($file, *%changes) {
%changes.=map({; .key.uc => .value });
my %seen;
 
my $out = open $tmpfile, :w;
 
for $file.IO.lines {
when /:s ^ ('#' .* | '') $/ {
say $out: ~$0;
}
when /:s ^ (';'+)? [(\w+) (\w+)?]? $/ {
next if !$1 or %seen{$1.uc}++;
my $new = %changes{$1.uc}:delete;
say $out: format-line $1, |( !defined($new) ?? ($2, !$0) !!
$new ~~ Bool ?? ($2, $new) !! ($new, True) );
}
default {
note "Malformed line: $_\nAborting.";
exit 1;
}
}
 
say $out: format-line .key, |(.value ~~ Bool ?? (Nil, .value) !! (.value, True))
for %changes;
 
move $tmpfile, $file;
}
 
END { unlink $tmpfile if $tmpfile.IO.e }
 
 
sub format-line ($key, $value, $enabled) {
("; " if !$enabled) ~ $key.uc ~ (" $value" if defined $value);
}
 
sub tmpfile {
$*SPEC.catfile: $*SPEC.tmpdir, ("a".."z").roll(20).join
}

PicoLisp[edit]

(let Data  # Read all data
(in "config"
(make
(until (eof)
(link (trim (split (line) " "))) ) ) )
(setq Data # Fix comments
(mapcar
'((L)
(while (head '(";" ";") (car L))
(pop L) )
(if (= '(";") (car L))
L
(cons NIL L) ) )
Data ) )
(let (Need NIL Seed NIL NBan NIL NStr NIL Favo NIL)
(map
'((L)
(let D (mapcar uppc (cadar L))
(cond
((= '`(chop "NEEDSPEELING") D)
(if Need
(set L)
(on Need)
(unless (caar L)
(set (car L) '(";")) ) ) )
((= '`(chop "SEEDSREMOVED") D)
(if Seed
(set L)
(on Seed)
(when (caar L)
(set (car L)) ) ) )
((= '`(chop "NUMBEROFBANANAS") D)
(if NBan
(set L)
(on NBan)
(set (cddar L) 1024) ) )
((= '`(chop "NUMBEROFSTRAWBERRIES") D)
(if NStr
(set L)
(on NStr) ) )
((= '`(chop "FAVOURITEFRUIT") D)
(if Favo
(set L)
(on Favo) ) ) ) ) )
Data )
(unless Need
(conc Data (cons (list NIL "NEEDSPEELING"))) )
(unless Seed
(conc Data (cons (list NIL "SEEDSREMOVED"))) )
(unless NBan
(conc Data (cons (list NIL "NUMBEROFBANANAS" 1024))) )
(unless NStr
(conc Data (cons (list NIL "NUMBEROFSTRAWBERRIES" 62000))) ) )
(out "config"
(for L Data
(prinl (glue " " (if (car L) L (cdr L)))) ) ) )

PowerShell[edit]

 
function Update-ConfigurationFile
{
[CmdletBinding()]
Param
(
[Parameter(Mandatory=$false,
Position=0)]
[ValidateScript({Test-Path $_})]
[string]
$Path = ".\config.txt",
 
[Parameter(Mandatory=$false)]
[string]
$FavouriteFruit,
 
[Parameter(Mandatory=$false)]
[int]
$NumberOfBananas,
 
[Parameter(Mandatory=$false)]
[int]
$NumberOfStrawberries,
 
[Parameter(Mandatory=$false)]
[ValidateSet("On", "Off")]
[string]
$NeedsPeeling,
 
[Parameter(Mandatory=$false)]
[ValidateSet("On", "Off")]
[string]
$SeedsRemoved
)
 
[string[]]$lines = Get-Content $Path
 
Clear-Content $Path
 
if (-not ($lines | Select-String -Pattern "^\s*NumberOfStrawberries" -Quiet))
{
"", "# How many strawberries we have", "NumberOfStrawberries 0" | ForEach-Object {$lines += $_}
}
 
foreach ($line in $lines)
{
$line = $line -replace "^\s*","" ## Strip leading whitespace
 
if ($line -match "[;].*\s*") {continue} ## Strip semicolons
 
switch -Regex ($line)
{
"(^$)|(^#\s.*)" ## Blank line or comment
{
$line = $line
}
"^FavouriteFruit\s*.*" ## Parameter FavouriteFruit
{
if ($FavouriteFruit)
{
$line = "FAVOURITEFRUIT $FavouriteFruit"
}
}
"^NumberOfBananas\s*.*" ## Parameter NumberOfBananas
{
if ($NumberOfBananas)
{
$line = "NUMBEROFBANANAS $NumberOfBananas"
}
}
"^NumberOfStrawberries\s*.*" ## Parameter NumberOfStrawberries
{
if ($NumberOfStrawberries)
{
$line = "NUMBEROFSTRAWBERRIES $NumberOfStrawberries"
}
}
".*NeedsPeeling\s*.*" ## Parameter NeedsPeeling
{
if ($NeedsPeeling -eq "On")
{
$line = "NEEDSPEELING"
}
elseif ($NeedsPeeling -eq "Off")
{
$line = "; NEEDSPEELING"
}
}
".*SeedsRemoved\s*.*" ## Parameter SeedsRemoved
{
if ($SeedsRemoved -eq "On")
{
$line = "SEEDSREMOVED"
}
elseif ($SeedsRemoved -eq "Off")
{
$line = "; SEEDSREMOVED"
}
}
Default ## Whatever...
{
$line = $line
}
}
 
Add-Content $Path -Value $line -Force
}
}
 
 
Update-ConfigurationFile -NumberOfStrawberries 62000 -NumberOfBananas 1024 -SeedsRemoved On -NeedsPeeling Off
 
Invoke-Item -Path ".\config.txt"
 
Output:
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024

# How many strawberries we have
NUMBEROFSTRAWBERRIES 62000

Python[edit]

#!/usr/bin/env python
 
#----------------------------------------------------------------------------
# STANDARD MODULES
#----------------------------------------------------------------------------
import re
import string
 
 
#----------------------------------------------------------------------------
# GLOBAL: VARIABLES
#----------------------------------------------------------------------------
DISABLED_PREFIX = ';'
 
 
#----------------------------------------------------------------------------
# CLASS Option
#----------------------------------------------------------------------------
class Option(object):
"""An option, characterized by its name and its (optional) value. and by
its status, which can be enabled or disabled.
If its value is None, it is regarded to as a boolean option with a
value of true.
"""

 
#------------------------------------------------------------------------
def __init__(self, name, value=None, disabled=False,
disabled_prefix=DISABLED_PREFIX):
"""Create an Option instance, setting its name to 'name' (always
converted to a string) and its value to 'value'. If 'disabled' is
True, the option is considered disabled, otherwise enabled.
The string 'disabled_prefix' is used as a prefix when generating the
string representation of the option.
"""

self.name = str(name)
self.value = value
self.disabled = bool(disabled)
self.disabled_prefix = disabled_prefix
 
#------------------------------------------------------------------------
def __str__(self):
"""Return a string representation of the Option instance.
This always includes the option name, followed by a space and the
option value (if it is not None). If the option is disabled, the
whole string is preprendend by the string stored in the instance
attribute 'disabled_prefix' and a space.
"""

disabled = ('', '%s ' % self.disabled_prefix)[self.disabled]
value = (' %s' % self.value, '')[self.value is None]
return ''.join((disabled, self.name, value))
 
#------------------------------------------------------------------------
def get(self):
"""Return the option value.
If the stored value is None, the option is regarded to as a
boolean one and its enabled status is returned. Othrwise its value
is returned.
"""

enabled = not bool(self.disabled)
if self.value is None:
value = enabled
else:
value = enabled and self.value
return value
 
 
#----------------------------------------------------------------------------
# CLASS Config
#----------------------------------------------------------------------------
class Config(object):
"""A set of configuration options and comment strings.
"""

# Regular expression matching a valid option line.
reOPTION = r'^\s*(?P<disabled>%s*)\s*(?P<name>\w+)(?:\s+(?P<value>.+?))?\s*$'
 
#------------------------------------------------------------------------
def __init__(self, fname=None, disabled_prefix=DISABLED_PREFIX):
"""Initialize a Config instance, optionally reading the contents of
the configuration file 'fname'.
The string 'disabled_prefix' is used as a prefix when generating the
string representation of the options.
"""

self.disabled_prefix = disabled_prefix
self.contents = [] # Sequence of strings and Option instances.
self.options = {} # Map an option name to an Option instance.
self.creOPTION = re.compile(self.reOPTION % self.disabled_prefix)
if fname:
self.parse_file(fname)
 
#------------------------------------------------------------------------
def __str__(self):
"""Return a string representation of the Config instance.
This is just the concatenation of all the items stored in the
attribute 'contents'.
"""

return '\n'.join(map(str, self.contents))
 
#------------------------------------------------------------------------
def parse_file(self, fname):
"""Parse all the lines of file 'fname' by applying the method
'parser_lines' on the file contents.
"""

with open(fname) as f:
self.parse_lines(f)
return self
 
#------------------------------------------------------------------------
def parse_lines(self, lines):
"""Parse all the lines of iterable 'lines' by invoking the method
'parse_line' for each line in 'lines'.
"""

for line in lines:
self.parse_line(line)
return self
 
#------------------------------------------------------------------------
def parse_line(self, line):
"""Parse the line 'line', looking for options.
If an option line is found, spaces are stripped from the start and
the end of 'line' and any non-printable character is removed as well.
Only the first occurrence of an option is processed, all the other
occurrences are ignored. A valid option is added to the instance
attribute 'contents' (in order to preserve its position among the
other lines). It is also added to the mapping stored in the instance
attribute 'options'.
Any non-option string is added the the instance attribute 'contents',
except those lines starting with the string stored into the instance
attribute 'disabled_prefix' which are not followed by any option
name.
"""

s = ''.join(c for c in line.strip() if c in string.printable)
moOPTION = self.creOPTION.match(s)
if moOPTION:
name = moOPTION.group('name').upper()
if not name in self.options:
self.add_option(name, moOPTION.group('value'),
moOPTION.group('disabled'))
else:
if not s.startswith(self.disabled_prefix):
self.contents.append(line.rstrip())
return self
 
#------------------------------------------------------------------------
def add_option(self, name, value=None, disabled=False):
"""Create a new Option instance, named 'name' (always converted to
uppercase) with value 'value' and set its disabled status to
'disabled'.
The Option instance is added to the instance attribute 'contents'.
It is also added to the mapping stored in the instance attribute
'options'.
"""

name = name.upper()
opt = Option(name, value, disabled)
self.options[name] = opt
self.contents.append(opt)
return opt
 
#------------------------------------------------------------------------
def set_option(self, name, value=None, disabled=False):
"""Look for an option named 'name' (always converted to
uppercase) among the options stored in the instance
attribute 'options'.
If it is not found, a new Option instance is created.
In any case its value is set to 'value' and its disabled
status to 'disabled'.
"""

name = name.upper()
opt = self.options.get(name)
if opt:
opt.value = value
opt.disabled = disabled
else:
opt = self.add_option(name, value, disabled)
return opt
 
#------------------------------------------------------------------------
def enable_option(self, name, value=None):
"""Enable the option named 'name' (always converted to
uppercase) and set its value to 'value'.
If the option is not found, it is created and added to the
end of the instance attribute 'contents'.
"""

return self.set_option(name, value, False)
 
#------------------------------------------------------------------------
def disable_option(self, name, value=None):
"""Disable the option named 'name' (always converted to
uppercase) and set its value to 'value'.
If the option is not found, it is created and added to the
end of the instance attribute 'contents'.
"""

return self.set_option(name, value, True)
 
#------------------------------------------------------------------------
def get_option(self, name):
"""Return the value of the option named 'name' (always
converted to uppercase).
If the option is not found in the instance attribute
'options', None is returned. If the stored value is None,
it is regarded to as a boolean option and its enable status
is returned. Otherwise its value is returned.
"""

opt = self.options.get(name.upper())
value = opt.get() if opt else None
return value
 
 
#----------------------------------------------------------------------------
# MAIN
#----------------------------------------------------------------------------
if __name__ == '__main__':
import sys
cfg = Config(sys.argv[1] if len(sys.argv) > 1 else None)
cfg.disable_option('needspeeling')
cfg.enable_option('seedsremoved')
cfg.enable_option('numberofbananas', 1024)
cfg.enable_option('numberofstrawberries', 62000)
print cfg
 

Output:

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024

NUMBEROFSTRAWBERRIES 62000

Racket[edit]

Use the shared options.rkt code.

 
#lang racket
 
(require "options.rkt")
 
 
(read-options "options-file")
(define-options needspeeling seedsremoved numberofbananas numberofstrawberries)
 
;; Disable the needspeeling option (using a semicolon prefix)
(set! needspeeling #f)
;; Enable the seedsremoved option by removing the semicolon and any
;; leading whitespace
(set! seedsremoved ENABLE)
;; Change the numberofbananas parameter to 1024
(set! numberofbananas 1024)
;; Enable (or create if it does not exist in the file) a parameter for
;; numberofstrawberries with a value of 62000
(set! numberofstrawberries 62000)
 

REXX[edit]

version 1[edit]

This REXX program was written to be executed under the Microsoft version of DOS   (with or without Windows).

Method note:

  • records are written (if appropriate) to a temporary file   (in the     \TEMP     folder)
  • if any changes (or deletions) were made, the original file is replaced with the temporary file
  • if no changes were made, the original file is left intact
  • the temporary file is always deleted on completion of the REXX program's execution

Programming note:   not all REXXes support the closing of files using the   lineout   BIF with a single argument.

/*REXX program demonstrates how to  update  a configuration file  (four specific tasks).*/
parse arg iFID oFID . /*obtain optional arguments from the CL*/
if iFID=='' | iFID=="," then iFID= 'UPDATECF.TXT' /*Not given? Then use default.*/
if oFID=='' | oFID=="," then oFID='\TEMP\UPDATECF.$$$' /* " " " " " */
call lineout iFID; call lineout oFID /*close the input and the output files.*/
$.=0 /*placeholder of the options detected. */
call dos 'ERASE' oFID /*erase a file (with no error message).*/
changed=0 /*nothing changed in the file (so far).*/
/* [↓] read the entire config file. */
do rec=0 while lines(iFID)\==0 /*read a record; bump the record count.*/
z=linein(iFID); zz=space(z) /*get record; elide extraneous blanks.*/
say '───────── record:' z /*echo the record just read ──► console*/
a=left(zz,1); _=space( translate(zz, ,';') ) /*_: is used to elide multiple ";" */
if zz=='' | a=='#' then do; call cpy z; iterate; end /*blank or a comment.*/
if _=='' then do; changed=1; iterate; end /*elide any semicolons; empty records.*/
parse upper var z op . /*obtain the option from the record. */
/* [↓] option may have leading or ···*/
if a==';' then do; parse upper var z 2 op . /*trailing blanks.*/
if op='SEEDSREMOVED' then call new space( substr(z, 2) )
call cpy z; $.op=1 /*write the Z record to the output file*/
iterate /*rec*/ /* ··· and then go read the next record*/
end
if $.op then do; changed=1; iterate; end /*is the option already defined? */
$.op=1 /* [↑] Yes? Then delete it. */
if op=='NEEDSPEELING' then call new ";" z
if op=='NUMBEROFBANANAS' then call new op 1024
if op=='NUMBEROFSTRAWBERRIES' then call new op 62000
call cpy z /*write the Z record to the output file*/
end /*rec*/
 
nos='NUMBEROFSTRAWBERRIES' /* [↓] Does NOS option need updating? */
if \$.nos then do; call new nos 62000; call cpy z; end /*update option.*/
call lineout iFID; call lineout oFID /*close the input and the output files.*/
if rec==0 then do; say "ERROR: input file wasn't found:" iFID; exit; end
if changed then do /*possibly overwrite the input file. */
call dos 'XCOPY' oFID iFID '/y /q',">nul" /*quietly*/
say; say center('output file', 79, "▒") /*title. */
call dos 'TYPE' oFID /*display content of the output file. */
end
call dos 'ERASE' oFID /*erase a file (with no error message).*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
cpy: call lineout oFID, arg(1); return /*write one line of text ───► oFID. */
dos: ''arg(1) word(arg(2) "2>nul",1); return /*execute a DOS command (quietly). */
new: z=arg(1); changed=1; return /*use new Z, indicate changed record. */

output   when using the default input file (which has additional removable statements) and input options:

───────── record: # This is a configuration file in standard configuration file format
───────── record: #
───────── record: # Lines beginning with a hash or a semicolon are ignored by the application
───────── record: # program. Blank lines are also ignored by the application program.
───────── record: ;
───────── record: ;;;
───────── record: ; ; ;
───────── record: ; ;; ;
───────── record:
───────── record: # The first word on each non comment line is the configuration option.
───────── record: # Remaining words or numbers on the line are configuration parameter
───────── record: # data fields.
───────── record:
───────── record: # Note that configuration option names are not case sensitive. However,
───────── record: # configuration parameter data is case sensitive and the lettercase must
───────── record: # be preserved.
───────── record:
───────── record: # This is a favourite fruit
───────── record: FAVOURITEFRUIT banana
───────── record: FAVOURITEFRUIT not bananas
───────── record:
───────── record: # This is a boolean that should be set
───────── record: NEEDSPEELING
───────── record:
───────── record: # This boolean is commented out
───────── record: ; SEEDSREMOVED
───────── record:
───────── record: # How many bananas we have
───────── record: NUMBEROFBANANAS 48
───────── record: NUMBEROFBANANAS forty-eight

▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒output file▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000

version 2[edit]

fid='updatecf.txt'
oid='updatecf.xxx'; 'erase' oid
options=translate('FAVOURITEFRUIT NEEDSPEELING SEEDSREMOVED NUMBEROFBANANAS numberofstrawberries')
done.=0
Do While lines(fid)>0
l=linein(fid)
c=left(l,1)
option=''
If c='#' | l='' Then
call o l
Else Do
If c=';' Then l=substr(l,3)
Parse Upper Var l option value
Select
When option='NEEDSPEELING' Then
Call o ';' option
When option='SEEDSREMOVED' Then
Call o option
When option='NUMBEROFBANANAS' Then
Call o option 1024
When option='FAVOURITEFRUIT' Then
Call o l
When option='NUMBEROFSTRAWBERRIES' Then
Call o option 62000
Otherwise
Call o '>>>' l
End
End
End
Do while options<>''
Parse Var options option options
If done.option=0 Then
Call o option 62000
End
Exit
o:
If option<>'' & done.option Then
Say 'Duplicate' option 'ignored'
Else Do
Call lineout oid,arg(1)
done.option=1
End
Return
Output:

same as for solution 'D'

Ruby[edit]

require 'stringio'
 
class ConfigFile
 
# create a ConfigFile object from a file
def self.file(filename)
fh = File.open(filename)
obj = self.new(fh)
obj.filename = filename
fh.close
obj
end
 
# create a ConfigFile object from a string
def self.data(string)
fh = StringIO.new(string)
obj = self.new(fh)
fh.close
obj
end
 
def initialize(filehandle)
@lines = filehandle.readlines
@filename = nil
tidy_file
end
attr :filename
 
def save()
if @filename
File.open(@filename, "w") {|f| f.write(self)}
end
end
 
def tidy_file()
@lines.map! do |line|
# remove leading whitespace
line.lstrip!
 
if line.match(/^#/)
# Lines beginning with hash symbols should not be manipulated and left
# unchanged in the revised file.
line
else
# replace double semicolon prefixes with just a single semicolon
line.sub!(/^;+\s+/, "; ")
 
if line.match(/^; \s*$/)
# Any lines beginning with a semicolon or groups of semicolons, but no
# following option should be removed
line = ""
else
# remove ... any trailing whitespace on the lines
line = line.rstrip + "\n"
 
# Whitespace between the option and paramters should consist only of a
# single space
if m = line.match(/^(; )?([[:upper:]]+)\s+(.*)/)
line = (m[1].nil? ? "" : m[1]) + format_line(m[2], m[3])
end
end
 
line
end
end
end
 
def format_line(option, value)
"%s%s\n" % [option.upcase.strip, value.nil? ? "" : " " + value.to_s.strip]
end
 
# returns the index of the option, or nil if not found
def find_option(option)
@lines.find_index {|line| line.match(/^#{option.upcase.strip}\b/)}
end
 
# uncomments a disabled option
def enable_option(option)
if idx = find_option("; " + option)
@lines[idx][/^; /] = ""
end
end
 
# comment a line with a semi-colon
def disable_option(option)
if idx = find_option(option)
@lines[idx][/^/] = "; "
end
end
 
# add an option, or change the value of an existing option.
# use nil for the value to set a boolean option
def set_value(option, value)
if idx = find_option(option)
@lines[idx] = format_line(option, value)
else
@lines << format_line(option, value)
end
end
 
def to_s
@lines.join('')
end
end
 
 
config = ConfigFile.data(DATA.read)
config.disable_option('needspeeling')
config.enable_option('seedsremoved')
config.set_value('numberofbananas', 1024)
config.set_value('numberofstrawberries', 62000)
puts config
 
 
__END__
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.
 
# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.
 
# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.
 
# This is a favourite fruit
FAVOURITEFRUIT banana
 
# This is a boolean that should be set
NEEDSPEELING
 
# This boolean is commented out
;;; SEEDSREMOVED
;;;
 
# How many bananas we have
NUMBEROFBANANAS 48

outputs

# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024

NUMBEROFSTRAWBERRIES 62000

Tcl[edit]

Creating this to be a general solution:

package require Tcl 8.6
oo::class create Config {
variable filename contents
constructor fileName {
set filename $fileName
set contents {}
try {
set f [open $filename]
### Sanitize during input
foreach line [split [read $f] \n] {
if {[string match "#*" $line]} {
lappend contents $line
continue
}
if {[regexp {^;\W*$} $line]} continue
set line [string trim [regsub -all {[^\u0020-\u007e]} $line {}]]
if {[regexp {^(\W*)(\w+)(.*)$} $line -> a b c]} {
set line "[regsub -all {^;+} $a {;}][string toupper $b]$c"
}
lappend contents $line
}
} finally {
if {[info exists f]} {
close $f
}
}
}
method save {} {
set f [open $filename w]
puts $f [join $contents \n]
close $f
}
 
# Utility methods (not exposed API)
method Transform {pattern vars replacement} {
set matched 0
set line -1
set RE "(?i)^$pattern$"
foreach l $contents {
incr line
if {[uplevel 1 [list regexp $RE $l -> {*}$vars]]} {
if {$matched} {
set contents [lreplace $contents $line $line]
incr line -1
} else {
lset contents $line [uplevel 1 [list subst $replacement]]
}
set matched 1
}
}
return $matched
}
method Format {k v} {
set v " [string trimleft $v]"
return "[string toupper $k][string trimright $v]"
}
 
# Public API for modifying options
method enable {option} {
if {![my Transform ";?\\s*($option)\\M\s*(.*)" {k v} \
{[my Format $k $v]}]} {
lappend contents [my Format $option ""]
}
}
method disable {option} {
if {![my Transform ";?\\s*($option)\\M\s*(.*)" {k v} \
{; [my Format $k $v]}]} {
lappend contents "; [my Format $option ""]"
}
}
method set {option {value ""}} {
if {![my Transform ";?\\s*($option)\\M.*" k {[my Format $k $value]}]} {
lappend contents [my Format $option $value]
}
}
}

Applying to the task at hand (assuming a file in the current directory called sample.cfg):

set cfg [Config new "sample.cfg"]
$cfg disable needspeeling
$cfg enable seedsremoved
$cfg set numberofbananas 1024
$cfg set numberofstrawberries 62000
$cfg save

TXR[edit]

This is a general solution which implements a command-line tool for updating the config file. Omitted are the trivial steps for writing the configuration back into the same file; the final result is output on standard output.

The first argument is the name of the config file. The remaining arguments are of this form:

  VAR      # define or update VAR as a true-valued boolean
  VAR=     # ensure "; VAR" in the config file.
  VAR=VAL  # ensure "VAR VAL" in the config file

This works by reading the configuration into a variable, and then making multiple passes over it, using the same constructs that normally operate on files or pipes. The first 30% of the script deals with reading the configuration file and parsing each command line argument, and converting its syntax into configuration syntax, stored in new_opt_line. For each argument, the configuration is then scanned and filtered from config to new_config, using the same syntax which could be used to do the same job with temporary files. When the interesting variable is encountered in the config, using one of the applicable pattern matches, then the prepared configuration line is substituted for it. While this is going on, the encountered variable names (bindings for var_other) are also being collected into a list. This list is then later used to check via the directive @(bind opt_there option) to determine whether the option occurred in the configuration or not. The bind construct will not only check whether the left and right hand side are equal, but if nested lists are involved, it checks whether either side occurs in the other as a subtree. option binds with opt_other if it matches one of the option names in opt_other. Finally, the updated config is regurgitated.

@(next :args)
@configfile
@(maybe)
@ (next configfile)
@ (collect :vars (config))
@config
@ (end)
@(end)
@(collect)
@ (cases)
@option=
@ (output :into new_opt_line :filter :upcase)
; @option
@ (end)
@ (or)
@[email protected]
@ (output :into new_opt_line :filter :upcase)
@option @val
@ (end)
@ (or)
@option
@ (output :into new_opt_line :filter :upcase)
@option
@ (end)
@ (end)
@ (next :var config)
@ (local new_config)
@ (bind new_config ())
@ (collect :vars ((opt_there "")))
@ (block)
@ (cases)
@ (cases)
@{line /[ \t]*/}
@ (or)
@{line /#.*/}
@ (end)
@ (output :append :into new_config)
@line
@ (end)
@ (accept)
@ (or)
@ (maybe)
; @opt_there
@ (or)
@opt_there @(skip)
@ (or)
@opt_there
@ (or)
@original_line
@ (end)
@ (end)
@ (cases)
@ (bind opt_there option :filter :upcase)
@ (output :append :into new_config)
@new_opt_line
@ (end)
@ (or)
@ (output :append :into new_config)
@original_line
@ (end)
@ (end)
@ (end)
@ (cases)
@ (bind opt_there option :filter :upcase)
@ (or)
@ (output :append :into new_config)
@new_opt_line
@ (end)
@ (end)
@ (set config new_config)
@(end)
@(output)
@ (repeat)
@config
@ (end)
@(end)

Sample invocation:

$ txr configfile2.txr configfile NEEDSPEELING= seedsREMOVED NUMBEROFBANANAS=1024 NUMBEROFSTRAWBERRIES=62000
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000

Test run on empty input:

$ echo -n | txr configfile2.txr - NEEDSPEELING= SEEDSREMOVED NUMBEROFBANANAS=1024 NUMBEROFSTRAWBERRIES=62000
; NEEDSPEELING
SEEDSREMOVED
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000

Test run on empty input with no arguments

$ echo -n | txr configfile2.txr -
[ no output ]

VBScript[edit]

 
Set objFSO = CreateObject("Scripting.FileSystemObject")
 
'Paramater lookups
Set objParamLookup = CreateObject("Scripting.Dictionary")
With objParamLookup
.Add "FAVOURITEFRUIT", "banana"
.Add "NEEDSPEELING", ""
.Add "SEEDSREMOVED", ""
.Add "NUMBEROFBANANAS", "1024"
.Add "NUMBEROFSTRAWBERRIES", "62000"
End With
 
'Open the config file for reading.
Set objInFile = objFSO.OpenTextFile(objFSO.GetParentFolderName(WScript.ScriptFullName) &_
"\IN_config.txt",1)
'Initialize output.
Output = ""
Isnumberofstrawberries = False
With objInFile
Do Until .AtEndOfStream
line = .ReadLine
If Left(line,1) = "#" Or line = "" Then
Output = Output & line & vbCrLf
ElseIf Left(line,1) = " " And InStr(line,"#") Then
Output = Output & Mid(line,InStr(1,line,"#"),1000) & vbCrLf
ElseIf Replace(Replace(line,";","")," ","") <> "" Then
If InStr(1,line,"FAVOURITEFRUIT",1) Then
Output = Output & "FAVOURITEFRUIT" & " " & objParamLookup.Item("FAVOURITEFRUIT") & vbCrLf
ElseIf InStr(1,line,"NEEDSPEELING",1) Then
Output = Output & "; " & "NEEDSPEELING" & vbCrLf
ElseIf InStr(1,line,"SEEDSREMOVED",1) Then
Output = Output & "SEEDSREMOVED" & vbCrLf
ElseIf InStr(1,line,"NUMBEROFBANANAS",1) Then
Output = Output & "NUMBEROFBANANAS" & " " & objParamLookup.Item("NUMBEROFBANANAS") & vbCrLf
ElseIf InStr(1,line,"NUMBEROFSTRAWBERRIES",1) Then
Output = Output & "NUMBEROFSTRAWBERRIES" & " " & objParamLookup.Item("NUMBEROFSTRAWBERRIES") & vbCrLf
Isnumberofstrawberries = True
End If
End If
Loop
If Isnumberofstrawberries = False Then
Output = Output & "NUMBEROFSTRAWBERRIES" & " " & objParamLookup.Item("NUMBEROFSTRAWBERRIES") & vbCrLf
Isnumberofstrawberries = True
End If
.Close
End With
 
'Create a new config file.
Set objOutFile = objFSO.OpenTextFile(objFSO.GetParentFolderName(WScript.ScriptFullName) &_
"\OUT_config.txt",2,True)
With objOutFile
.Write Output
.Close
End With
 
Set objFSO = Nothing
Set objParamLookup = Nothing
 
Input:
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
    # be preserved.

# This is a favourite fruit
FAVOURITEFRUIT    ßßßßß		banana    µµµµ

# This is a boolean that should be set
NEEDspeeling

# This boolean is commented out
;;;; SEEDSREMOVED µµµµµ
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

# How many bananas we have
    NUMBEROFBANANAS µµµµµ 48
Output:
# This is a configuration file in standard configuration file format
#
# Lines begininning with a hash or a semicolon are ignored by the application
# program. Blank lines are also ignored by the application program.

# The first word on each non comment line is the configuration option.
# Remaining words or numbers on the line are configuration parameter
# data fields.

# Note that configuration option names are not case sensitive. However,
# configuration parameter data is case sensitive and the lettercase must
# be preserved.

# This is a favourite fruit
FAVOURITEFRUIT banana

# This is a boolean that should be set
; NEEDSPEELING

# This boolean is commented out
SEEDSREMOVED

# How many bananas we have
NUMBEROFBANANAS 1024
NUMBEROFSTRAWBERRIES 62000