Update a configuration file: Difference between revisions

{{header|TXR}}

{{works with|TXR git head}}

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:

<pre>

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

</pre>

<lang txr>@(next :args)

@configfile

@(maybe)

@ (next configfile)

@ (collect)

@config

@ (end)

@(end)

@(collect)

@ (cases)

@option=

@ (output :into new_opt_line)

; @option

@ (end)

@ (or)

@option=@val

@ (output :into new_opt_line)

@option @val

@ (end)

@ (or)

@option

@ (output :into new_opt_line)

@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)

@ (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)

@ (or)

@ (output :append :into new_config)

@new_opt_line

@ (end)

@ (end)

@ (set config new_config)

@(end)

@(output)

@ (repeat)

@config

@ (end)

@(end)</lang>

Sample invocation:

<pre>$ 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</pre>