Read a specific line from a file: Difference between revisions

Line 18:

=={{header|11l}}==

<~~lang~~ 11l>V f = File(‘input.txt’)

<syntaxhighlight lang="11l">V f = File(‘input.txt’)

V line = 3

L 0 .< line - 1

f.read_line()

print(f.read_line())</~~lang~~>

print(f.read_line())</syntaxhighlight>

=={{header|Action!}}==

In the following solution the input file is loaded from H6 drive. Altirra emulator automatically converts CR/LF character from ASCII into 155 character in ATASCII charset used by Atari 8-bit computer when one from H6-H10 hard drive under DOS 2.5 is used.

<~~lang~~ ~~Action~~!>BYTE FUNC ReadLine(CHAR ARRAY fname CARD index CHAR ARRAY result)

<syntaxhighlight lang="action!">BYTE FUNC ReadLine(CHAR ARRAY fname CARD index CHAR ARRAY result)

CHAR ARRAY line(255)

CARD curr

Line 72:

Test(fname,24)

Test(fname,50)

RETURN</~~lang~~>

RETURN</syntaxhighlight>

[https://gitlab.com/amarok8bit/action-rosetta-code/-/raw/master/images/Read_a_specific_line_from_a_file.png Screenshot from Atari 8-bit computer]

Line 91:

=={{header|Ada}}==

<~~lang~~ ada>with Ada.Text_IO; use Ada.Text_IO;

<syntaxhighlight lang="ada">with Ada.Text_IO; use Ada.Text_IO;

procedure Rosetta_Read is

Line 119:

Put_Line ("Line 7 is too long to load.");

Close (File);

end Rosetta_Read;</~~lang~~>

end Rosetta_Read;</syntaxhighlight>

=={{header|Aime}}==

<~~lang~~ aime>void

<syntaxhighlight lang="aime">void

read_line(text &line, text path, integer n)

{

Line 147:

0;

}</~~lang~~>

}</syntaxhighlight>

=={{header|ALGOL 68}}==

<~~lang~~ algol68># reads the line with number "number" (counting from 1) #

<syntaxhighlight lang="algol68"># reads the line with number "number" (counting from 1) #

# from the file named "file name" and returns the text of the #

# in "line". If an error occurs, the result is FALSE and a #

Line 220:

print( ( "unable to read line: """ + err + """" ) )

FI

)</~~lang~~>

)</syntaxhighlight>

=={{header|Amazing Hopper}}==

#include <hopper.h>

#define MAX_LINE_SIZE 1000

Line 238:

fclose(fd)

exit(0)

</syntaxhighlight>

</lang>

<pre>

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=={{header|AutoHotkey}}==

<~~lang~~ ~~AutoHotkey~~>FileReadLine, OutputVar, filename.txt, 7

<syntaxhighlight lang="autohotkey">FileReadLine, OutputVar, filename.txt, 7

if ErrorLevel

MsgBox, There was an error reading the 7th line of the file</~~lang~~>

MsgBox, There was an error reading the 7th line of the file</syntaxhighlight>

=={{header|AWK}}==

<~~lang~~ awk>#!/usr/bin/awk -f

<syntaxhighlight lang="awk">#!/usr/bin/awk -f

#usage: readnthline.awk -v lineno=6 filename

Line 263:

print storedline

}

</syntaxhighlight>

</lang>

=={{header|BASIC}}==

==={{header|BASIC256}}===

<~~lang~~ basic256>f = freefile

<syntaxhighlight lang="basic256">f = freefile

filename$ = "input.txt"

open f, filename$

Line 283:

if cont < lineapedida then print "There are only "; cont; " lines in the file"

close f

end</~~lang~~>

end</syntaxhighlight>

==={{header|OxygenBasic}}===

library OOP

<lang>

uses stringutil

new Textarray t

Line 294:

' print t.lineCount

del t

</syntaxhighlight>

</lang>

==={{header|QBasic}}===

<~~lang~~ ~~QBasic~~>f = FREEFILE

<syntaxhighlight lang="qbasic">f = FREEFILE

OPEN "input.txt" FOR INPUT AS #f

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LOOP

IF cont < lineapedida THEN PRINT "There are only "; cont; " lines in the file"

CLOSE #1</~~lang~~>

CLOSE #1</syntaxhighlight>

==={{header|True BASIC}}===

<~~lang~~ qbasic>LET filename$ = "input.txt"

<syntaxhighlight lang="qbasic">LET filename$ = "input.txt"

OPEN #1: NAME filename$, ORG TEXT, ACCESS INPUT, CREATE OLD

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IF cont < lineapedida THEN PRINT "There are only "; cont; " lines in the file"

CLOSE #1

END</~~lang~~>

END</syntaxhighlight>

==={{header|Yabasic}}===

<~~lang~~ yabasic>filename$ = "input.txt"

<syntaxhighlight lang="yabasic">filename$ = "input.txt"

open filename$ for reading as #1

Line 348:

if cont < lineapedida print "There are only ", cont, " lines in the file"

close #1

end</~~lang~~>

end</syntaxhighlight>

=={{header|Batch File}}==

<~~lang~~ dos>

@echo off

Line 361:

echo Line 7 is: %line7%

pause>nul

</syntaxhighlight>

</lang>

<pre>

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=={{header|BBC BASIC}}==

<~~lang~~ bbcbasic> filepath$ = @lib$ + "..\licence.txt"

<syntaxhighlight lang="bbcbasic"> filepath$ = @lib$ + "..\licence.txt"

requiredline% = 7

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IF ASCtext$=10 text$ = MID$(text$,2)

PRINT text$</~~lang~~>

PRINT text$</syntaxhighlight>

=={{header|C}}==

Mmap file and search for offsets to certain line number. Since mapped file really is memory, there's no extra storage procedure once offsets are found.

<~~lang~~ c>#include <unistd.h>

<syntaxhighlight lang="c">#include <unistd.h>

#include <sys/types.h>

#include <sys/mman.h>

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return ret;

}</~~lang~~>

}</syntaxhighlight>

===Alternate Version===

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This version does not rely on POSIX APIs such as <tt>mmap</tt>, but rather sticks to ANSI C functionality. This version also works with non-seekable files, so it can be fed by a pipe. It performs limited but adequate error checking. That is, <tt>get_nth_line</tt> returns NULL on all failures, and the caller can distinguish EOF, file read error and out of memory by calling <tt>feof()</tt> and <tt>ferror()</tt> on the input file.

<~~lang~~ c>#include <stdio.h>

<syntaxhighlight lang="c">#include <stdio.h>

#include <stdlib.h>

Line 569:

return 0;

}

</syntaxhighlight>

</lang>

=={{header|C sharp}}==

<~~lang~~ C sharp>using System;

<syntaxhighlight lang="c sharp">using System;

using System.IO;

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}

}</~~lang~~>

}</syntaxhighlight>

=={{header|C++}}==

<~~lang~~ cpp>#include <string>

<syntaxhighlight lang="cpp">#include <string>

#include <fstream>

#include <iostream>

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return 1 ;

}

}</~~lang~~>

}</syntaxhighlight>

=={{header|Clojure}}==

<~~lang~~ clojure>(defn read-nth-line

<syntaxhighlight lang="clojure">(defn read-nth-line

"Read line-number from the given text file. The first line has the number 1."

[file line-number]

(with-open [rdr (clojure.java.io/reader file)]

(nth (line-seq rdr) (dec line-number))))</~~lang~~>

(nth (line-seq rdr) (dec line-number))))</syntaxhighlight>

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=={{header|Common Lisp}}==

<~~lang~~ lisp>(defun read-nth-line (file n &aux (line-number 0))

<syntaxhighlight lang="lisp">(defun read-nth-line (file n &aux (line-number 0))

"Read the nth line from a text file. The first line has the number 1"

(assert (> n 0) (n))

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if (and line (= line-number n))

do (return line))))

</syntaxhighlight>

</lang>

Example call:

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=={{header|D}}==

simply

void main() {

import std.stdio, std.file, std.string;

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writeln((file_lines.length > 6) ? file_lines[6] : "line not found");

}

</syntaxhighlight>

</lang>

or, line by line

<~~lang~~ d>import std.stdio;

<syntaxhighlight lang="d">import std.stdio;

void main() {

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writefln("the file only contains %d lines", countLines);

}

}</~~lang~~>

}</syntaxhighlight>

<pre>

line 7: foreach (char[] line; f.byLine()) {</pre>

Line 723:

program Read_a_specific_line_from_a_file;

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Writeln(ReadLine(7, 'test'));

Readln;

end.</~~lang~~>

end.</syntaxhighlight>

=={{header|Elixir}}==

The idea is to stream the file, filter the elements and get the remaining element. If does not exist, nil will be throw and we will pattern match with print_line(_). If the value exists, it will match print_line({value, _line_number}) and the value of the line will be printed.

defmodule LineReader do

def get_line(filename, line) do

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defp print_line(_), do: {:error, "Invalid Line"}

end

</syntaxhighlight>

</lang>

=={{header|Erlang}}==

Using function into_list/1 from [[Read_a_file_line_by_line]].

There is no behaviour specified after printing an error message, so I throw an exception. An alternative would be to continue with a default value?

-module( read_a_specific_line ).

Line 813:

line_nr_error( function_clause ) -> too_few_lines_in_file;

line_nr_error( Error ) -> Error.

</syntaxhighlight>

</lang>

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=={{header|F_Sharp|F#}}==

<~~lang~~ fsharp>open System

<syntaxhighlight lang="fsharp">open System

open System.IO

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// if not not enough lines available

Console.WriteLine(line)

0</~~lang~~>

0</syntaxhighlight>

=={{header|Factor}}==

<~~lang~~ factor>USING: continuations fry io io.encodings.utf8 io.files kernel

<syntaxhighlight lang="factor">USING: continuations fry io io.encodings.utf8 io.files kernel

math ;

IN: rosetta-code.nth-line

Line 861:

print ;

MAIN: nth-line-demo</~~lang~~>

MAIN: nth-line-demo</syntaxhighlight>

=={{header|Fortran}}==

A lot of petty annoyances can arise in the attempt to complete the desired action, and so the function does not simply return ''true'' or ''false'', nor does it return some drab integer code that would require an auxiliary array of explanatory texts somewhere... Instead, it returns a message reporting on its opinion, with an ad-hoc scheme. If the first character is a space, all is well, otherwise a ! indicates some severe problem while a + indicates a partial difficulty. The text of the desired record is returned via a parameter, thus the caller can be the one responsible for deciding how much space to provide for it. F2000 has provision for allocating character strings of the needed length, but there is no attempt to use that here as the key requirement is for the length to be decided during the process of the READ statement.

The example uses F90 only because the MODULE protocol enables usage of a function without having to re-declare its type in every calling routine. Otherwise this is F77 style. Some compilers become confused or raise an error over the manipulation of a function's name as if it were an ordinary variable. In such a case an auxiliary variable can be used with its value assigned to the function name on exit.<~~lang~~ ~~Fortran~~> MODULE SAMPLER !To sample a record from a file. SAM00100

The example uses F90 only because the MODULE protocol enables usage of a function without having to re-declare its type in every calling routine. Otherwise this is F77 style. Some compilers become confused or raise an error over the manipulation of a function's name as if it were an ordinary variable. In such a case an auxiliary variable can be used with its value assigned to the function name on exit.<syntaxhighlight lang="fortran"> MODULE SAMPLER !To sample a record from a file. SAM00100

CONTAINS SAM00200

CHARACTER*20 FUNCTION GETREC(N,F,IS) !Returns a status. SAM00300

Line 933:

666 WRITE (MSG,*) "Can't get the record!" POK02700

END !That was easy. POK02800

</syntaxhighlight>

</lang>

Output:

<pre>

Line 953:

Obviously, this only works because of the special nature of the file being read. Other systems offer a filesystem that does not regard record sizes or separators as being a part of the record that is read or written, and in such a case, a CR (or CRLF, or whatever) does not appear amongst the data. Some systems escalate to enabling such random access for varying-length records, or access by a key text rather than a record number (so that a key of "SAM00700" might be specified), and acronyms such as ISAM start appearing.

In Fortran 77 there was no verbose REC=''n'' facility, instead one used <~~lang~~ ~~Fortran~~>READ (F'7) STUFF(1:80)</~~lang~~> - that is, an apostrophe even though an at-sign was available - and again the source file highlighting is confused. An interesting alternative was to use the FIND(F'7) statement instead, followed by an ordinary READ (or WRITE) not necessarily specifying the desired record number. The point of this is that the FIND statement would initiate the pre-positioning for the next I/O ''asynchronously'' so that other processing could intervene between it and the READ or WRITE, and in situations more complex than this example, there could be startling changes in performance. If not always positive ones when many files were being accessed on one physical disc drive. Unfortunately, later Fortran extensions have abandoned this statement, while multiprocessing has proliferated.

In Fortran 77 there was no verbose REC=''n'' facility, instead one used <syntaxhighlight lang="fortran">READ (F'7) STUFF(1:80)</syntaxhighlight> - that is, an apostrophe even though an at-sign was available - and again the source file highlighting is confused. An interesting alternative was to use the FIND(F'7) statement instead, followed by an ordinary READ (or WRITE) not necessarily specifying the desired record number. The point of this is that the FIND statement would initiate the pre-positioning for the next I/O ''asynchronously'' so that other processing could intervene between it and the READ or WRITE, and in situations more complex than this example, there could be startling changes in performance. If not always positive ones when many files were being accessed on one physical disc drive. Unfortunately, later Fortran extensions have abandoned this statement, while multiprocessing has proliferated.

The GO TO style of handling mishaps in an I/O statement makes a simple structure difficult - note that the reception area ought not be fallen into by normal execution, thus the STOP. Unfortunately, READ and WRITE statements do not return a result that could be tested in an IF-statement or WHILE-loop, but this can be approached with only a little deformation: <~~lang~~ ~~Fortran~~> READ (F,REC = 7,ERR = 666, IOSTAT = IOSTAT) STUFF(1:80)

The GO TO style of handling mishaps in an I/O statement makes a simple structure difficult - note that the reception area ought not be fallen into by normal execution, thus the STOP. Unfortunately, READ and WRITE statements do not return a result that could be tested in an IF-statement or WHILE-loop, but this can be approached with only a little deformation: <syntaxhighlight lang="fortran"> READ (F,REC = 7,ERR = 666, IOSTAT = IOSTAT) STUFF(1:80)

666 IF (IOSTAT.NE.0) THEN

WRITE (MSG,*) "Can't get the record: code",IOSTAT

ELSE

WRITE (MSG,1) "Record",STUFF(1:80)

END IF</~~lang~~>

END IF</syntaxhighlight>

Where IOSTAT is an integer variable (and also a key word) and this formulation means not having to remember which way the assignment goes; it is left to right. The error code numbers are unlikely to be the same across different systems, so experimentation is in order. It would be much nicer to be able to write something like <code>IF (READ (F,REC = 7, IOSTAT = IOSTAT) STUFF(1:80)) THEN ''etc.''</code> or <code>DO WHILE(''etc.'')</code>

=={{header|FreeBASIC}}==

<~~lang~~ freebasic>' FB 1.05.0 Win64

<syntaxhighlight lang="freebasic">' FB 1.05.0 Win64

Open "input.txt" For Input As #1

Line 989:

Print

Print "Press any key to quit"

Sleep </~~lang~~>

Sleep </syntaxhighlight>

=={{header|Frink}}==

<~~lang~~ frink>nthLine[filename, lineNum] :=

<syntaxhighlight lang="frink">nthLine[filename, lineNum] :=

{

line = nth[lines[filenameToURL[filename]], lineNum-1]

Line 1,002:

return undef

}

}</~~lang~~>

}</syntaxhighlight>

=={{header|FutureBasic}}==

Uses FB's openpanel command that opens a dialog window and allows the user to select the file to read.

<~~lang~~ futurebasic>window 1

<syntaxhighlight lang="futurebasic">window 1

long i = 1

Line 1,031:

end if

HandleEvents</~~lang~~>

HandleEvents</syntaxhighlight>

Input text file:

Line 1,052:

=={{header|Go}}==

<~~lang~~ go>package main

<syntaxhighlight lang="go">package main

import (

Line 1,102:

}

return line, nil

}</~~lang~~>

}</syntaxhighlight>

=={{header|Groovy}}==

<~~lang~~ groovy>def line = null

<syntaxhighlight lang="groovy">def line = null

new File("lines.txt").eachLine { currentLine, lineNumber ->

if (lineNumber == 7) {

Line 1,111:

}

println "Line 7 = $line"</~~lang~~>

println "Line 7 = $line"</syntaxhighlight>

=={{header|Haskell}}==

<~~lang~~ ~~Haskell~~>main :: IO ()

<syntaxhighlight lang="haskell">main :: IO ()

main = do contents <- readFile filename

case drop 6 $ lines contents of

[] -> error "File has less than seven lines"

l:_ -> putStrLn l

where filename = "testfile"</~~lang~~>

where filename = "testfile"</syntaxhighlight>

=={{header|Icon}} and {{header|Unicon}}==

Line 1,127:

While it is certainly possible to read at file at specific offsets without reading each line via ''seek'', with files using line feed terminated variable length records something has to read the data to determine the 7th record. This solution uses a combination of repeated alternation and generation limiting to achieve this. The counter is simply to discover if there are enough records.

<~~lang~~ ~~Icon~~>procedure main()

<syntaxhighlight lang="icon">procedure main()

write(readline("foo.bar.txt",7)|"failed")

end

Line 1,136:

close(f)

if i = 0 then return line

end</~~lang~~>

end</syntaxhighlight>

=={{header|J}}==

<~~lang~~ j>readLine=: 4 :0

<syntaxhighlight lang="j">readLine=: 4 :0

(x-1) {:: <;.2 ] 1!:1 boxxopen y

)</~~lang~~>

)</syntaxhighlight>

Thus:

<~~lang~~ bash>$ cal 2011 > cal.txt</~~lang~~>

<~~lang~~ j> 7 readLine 'cal.txt'

<syntaxhighlight lang="j"> 7 readLine 'cal.txt'

9 10 11 12 13 14 15 13 14 15 16 17 18 19 13 14 15 16 17 18 19</~~lang~~>

9 10 11 12 13 14 15 13 14 15 16 17 18 19 13 14 15 16 17 18 19</syntaxhighlight>

Note that this code assumes that the last character in the file is the line end character, and that the line end character is a part of the line to be retrieved.

'''Tacit alternative'''

<~~lang~~ j>require 'files' NB. required for versions before J701

<syntaxhighlight lang="j">require 'files' NB. required for versions before J701

readLineT=: <:@[ {:: 'b'&freads@]</~~lang~~>

readLineT=: <:@[ {:: 'b'&freads@]</syntaxhighlight>

This is not quite equivalent to the code above as it handles cross-platform line-endings and those line end character(s) are removed from the result.

Line 1,159:

<tt>example: java -cp . LineNbr7 LineNbr7.java</tt>

<tt>output : line 7: public static void main(String[] args) throws Exception {;</tt>

<~~lang~~ java>package linenbr7;

<syntaxhighlight lang="java">package linenbr7;

import java.io.*;

Line 1,191:

}

}</~~lang~~>

}</syntaxhighlight>

=={{header|jq}}==

Line 1,200:

* "foreach" - a control structure for iterating over a stream

* "break" - for breaking out of a loop

<~~lang~~ jq># Input - a line number to read, counting from 1

<syntaxhighlight lang="jq"># Input - a line number to read, counting from 1

# Output - a stream with 0 or 1 items

def read_line:

Line 1,206:

| label $top

| foreach inputs as $line

(0; .+1; if . == $in then $line, break $top else empty end) ;</~~lang~~>

(0; .+1; if . == $in then $line, break $top else empty end) ;</syntaxhighlight>

'''Example:''' Read line number $line (to be provided on the command line), counting from 1

<~~lang~~ jq>$line | tonumber

<syntaxhighlight lang="jq">$line | tonumber

| if . > 0 then read_line

else "$line (\(.)) should be a non-negative integer"

end</~~lang~~>

end</syntaxhighlight>

<~~lang~~ sh>$ jq -n -r 'range(0;20) | tostring' | jq --arg line 10 -n -R -r -f Read_a_specific_line_from_a_file.jq

<syntaxhighlight lang="sh">$ jq -n -r 'range(0;20) | tostring' | jq --arg line 10 -n -R -r -f Read_a_specific_line_from_a_file.jq

9</~~lang~~>

9</syntaxhighlight>

=={{header|Julia}}==

The short following snippet of code actually stores all the lines from the file in an array and displays the seventh element of the array, returning an error if there is no such element. Since the array is not referenced, it will be garbage collected when needed. The filehandle is closed upon completion of the task, be it successful or not.

<~~lang~~ ~~Julia~~>open(readlines, "path/to/file")[7]</~~lang~~>

<syntaxhighlight lang="julia">open(readlines, "path/to/file")[7]</syntaxhighlight>

The next function reads n lines in the file and displays the last read if possible, or returns a short message. Here again, the filehandle is automatically closed after the task. Note that the first line is returned if a negative number is given as the line number.

<~~lang~~ ~~Julia~~>function read_nth_lines(stream, num)

<syntaxhighlight lang="julia">function read_nth_lines(stream, num)

for i = 1:num-1

readline(stream)

Line 1,226:

result = readline(stream)

print(result != "" ? result : "No such line.")

end</~~lang~~>

end</syntaxhighlight>

<pre>julia> open(line -> read_nth_lines(line, 7), "path/to/file")

Line 1,232:

=={{header|Kotlin}}==

<~~lang~~ scala>// version 1.1.2

<syntaxhighlight lang="scala">// version 1.1.2

import java.io.File

Line 1,263:

Line 7

Line 8

*/</~~lang~~>

*/</syntaxhighlight>

Line 1,271:

=={{header|Lasso}}==

<~~lang~~ ~~Lasso~~>local(f) = file('unixdict.txt')

<syntaxhighlight lang="lasso">local(f) = file('unixdict.txt')

handle => { #f->close }

local(this_line = string,line = 0)

Line 1,280:

}

#this_line // 6th, which is the 7th line in the file

</syntaxhighlight>

</lang>

=={{header|Liberty BASIC}}==

We read the whole file into memory, and use 'word$( string, number, delimiter)'. Line delimiter is assumed to be CRLF, and the file is assumed to exist at the path given.

<~~lang~~ lb>fileName$ ="F:\sample.txt"

<syntaxhighlight lang="lb">fileName$ ="F:\sample.txt"

requiredLine =7

Line 1,294:

if line7$ =chr$( 13) +chr$( 10) or line7$ ="" then notice "Empty line! ( or file has fewer lines)."

print line7$</~~lang~~>

print line7$</syntaxhighlight>

=={{header|Lua}}==

<~~lang~~ lua>function fileLine (lineNum, fileName)

<syntaxhighlight lang="lua">function fileLine (lineNum, fileName)

local count = 0

for line in io.lines(fileName) do

Line 1,306:

end

print(fileLine(7, "test.txt"))</~~lang~~>

print(fileLine(7, "test.txt"))</syntaxhighlight>

=={{header|Maple}}==

<~~lang~~ ~~Maple~~>path := "file.txt":

<syntaxhighlight lang="maple">path := "file.txt":

specificLine := proc(path, num)

local i, input:

Line 1,318:

if i = num+1 then printf("Line %d, %s", num, input):

elif i <= num then printf ("Line number %d is not reached",num): end if:

end proc:</~~lang~~>

end proc:</syntaxhighlight>

=={{header|Mathematica}}/{{header|Wolfram Language}}==

<~~lang~~ ~~Mathematica~~> If[# != EndOfFile , Print[#]]& @ ReadList["file", String, 7]</~~lang~~>

<syntaxhighlight lang="mathematica"> If[# != EndOfFile , Print[#]]& @ ReadList["file", String, 7]</syntaxhighlight>

=={{header|MATLAB}} / {{header|Octave}}==

eln = 7; % extract line number 7

line = '';

Line 1,344:

end;

printf('line %i: %s\n',eln,line);

</~~lang~~>

</syntaxhighlight>

<nowiki>Insert non-formatted text here</nowiki>

=={{header|MoonScript}}==

<~~lang~~ ~~MoonScript~~>iter = io.lines 'test.txt'

<syntaxhighlight lang="moonscript">iter = io.lines 'test.txt'

for i=0, 5

error 'Not 7 lines in file' if not iter!

print iter!</~~lang~~>

print iter!</syntaxhighlight>

=={{header|Nanoquery}}==

<~~lang~~ ~~Nanoquery~~>def getline(fname, linenum)

<syntaxhighlight lang="nanoquery">def getline(fname, linenum)

contents = null

try

Line 1,368:

end

end</~~lang~~>

end</syntaxhighlight>

=={{header|NetRexx}}==

<~~lang~~ ~~NetRexx~~>/* NetRexx */

<syntaxhighlight lang="netrexx">/* NetRexx */

options replace format comments java crossref symbols nobinary

Line 1,423:

method isFalse() public static returns boolean

return \(1 == 1)

</syntaxhighlight>

</lang>

=={{header|Nim}}==

<~~lang~~ nim>import strformat

<syntaxhighlight lang="nim">import strformat

proc readLine(f: File; num: Positive): string =

Line 1,439:

echo f.readLine(7)

f.close()

</syntaxhighlight>

</lang>

=={{header|OCaml}}==

Line 1,445:

OCaml does not provide built-in facilities to obtain a particular line from a file. It only provides a function to read one line from a file from the current position in the input channel [http://caml.inria.fr/pub/docs/manual-ocaml/libref/Pervasives.html#VALinput_line input_line]. We can use this function to get the seventh line from a file, for example as follows:

<~~lang~~ ocaml>let input_line_opt ic =

<syntaxhighlight lang="ocaml">let input_line_opt ic =

try Some (input_line ic)

with End_of_file -> None

Line 1,465:

let () =

print_endline (nth_line 7 Sys.argv.(1))</~~lang~~>

print_endline (nth_line 7 Sys.argv.(1))</syntaxhighlight>

=={{header|PARI/GP}}==

Line 1,472:

=={{header|Pascal}}==

<~~lang~~ pascal>Program FileTruncate;

<syntaxhighlight lang="pascal">Program FileTruncate;

uses

Line 1,509:

Close(myfile);

writeln(line);

end.</~~lang~~>

end.</syntaxhighlight>

Output:

<pre>

Line 1,516:

=={{header|Perl}}==

<~~lang~~ perl>#!/usr/bin/perl -s

<syntaxhighlight lang="perl">#!/usr/bin/perl -s

# invoke as <scriptname> -n=7 [input]

while (<>) { $. == $n and print, exit }

die "file too short\n";</~~lang~~>

die "file too short\n";</syntaxhighlight>

=={{header|Phix}}==

No specific mechanism, but simple enough. If the file is suitably small:

object lines = get_text("TEST.TXT",GT_LF_STRIPPED)

if sequence(lines) and length(lines)>=7 then

Line 1,530:

?"no line 7"

end if

For bigger files:

integer fn = open("TEST.TXT","r")

for i=1 to 6 do

Line 1,539:

?gets(fn) -- (shows -1 if past eof)

close(fn)

=={{header|Phixmonti}}==

<~~lang~~ ~~Phixmonti~~>include ..\Utilitys.pmt

<syntaxhighlight lang="phixmonti">include ..\Utilitys.pmt

argument 1 get "r" fopen var f drop

Line 1,549:

f fgets number? if f fclose exitfor else nip nip endif

endfor

print /# show -1 if past eof #/</~~lang~~>

print /# show -1 if past eof #/</syntaxhighlight>

=={{header|PHP}}==

<~~lang~~ php><?php

<syntaxhighlight lang="php"><?php

$DOCROOT = $_SERVER['DOCUMENT_ROOT'];

Line 1,568:

if (!$fp) die("Input file not found!");

echo fileLine(7, $fp);

?></~~lang~~>

?></syntaxhighlight>

=={{header|PicoLisp}}==

<~~lang~~ ~~PicoLisp~~>(in "file.txt"

<syntaxhighlight lang="picolisp">(in "file.txt"

(do 6 (line))

(or (line) (quit "No 7 lines")) )</~~lang~~>

(or (line) (quit "No 7 lines")) )</syntaxhighlight>

=={{header|PL/I}}==

<~~lang~~ pli>

declare text character (1000) varying, line_no fixed;

Line 1,589:

put skip list (text);

next: ;

</syntaxhighlight>

</lang>

=={{header|PL/M}}==

This is written for the original 8080 PL/M compiler and can be run under CP/M or an emulator or clone.

The name of the file to read and the line number to read should be specified on the command line. E.g., if the source is in a file called READLINE.PLM and has been compiled to READLINE.COM, then the command <code>READLINE READLINE.PLM 7</code> would display the 7th line of the source.

<~~lang~~ pli>100H: /* READ A SPECIFIC LINE FROM A FILE */

<syntaxhighlight lang="pli">100H: /* READ A SPECIFIC LINE FROM A FILE */

DECLARE FALSE LITERALLY '0', TRUE LITERALLY '0FFH';

Line 1,726:

CALL EXIT;

EOF</~~lang~~>

EOF</syntaxhighlight>

=={{header|PowerShell}}==

$file = Get-Content c:\file.txt

if ($file.count -lt 7)

Line 1,738:

$file | Where Readcount -eq 7 | set-variable -name Line7

}

</syntaxhighlight>

</lang>

=={{header|PureBasic}}==

<~~lang~~ purebasic>Structure lineLastRead

<syntaxhighlight lang="purebasic">Structure lineLastRead

lineRead.i

line.s

Line 1,772:

MessageRequester("Error", "Couldn't open file " + filename + ".")

EndIf

EndIf </~~lang~~>

EndIf </syntaxhighlight>

=={{header|Python}}==

Line 1,778:

Using only builtins (note that <code>enumerate</code> is zero-based):

<~~lang~~ python>with open('xxx.txt') as f:

<syntaxhighlight lang="python">with open('xxx.txt') as f:

for i, line in enumerate(f):

if i == 6:

Line 1,784:

else:

print('Not 7 lines in file')

line = None</~~lang~~>

line = None</syntaxhighlight>

Using the <code>islice</code> iterator function from the [https://docs.python.org/3/library/itertools.html#itertools.islice itertools] standard library module, which applies slicing to an iterator and thereby skips over the first six lines:

<~~lang~~ python>from itertools import islice

<syntaxhighlight lang="python">from itertools import islice

with open('xxx.txt') as f:

Line 1,794:

line = next(islice(f, 6, 7))

except StopIteration:

print('Not 7 lines in file')</~~lang~~>

print('Not 7 lines in file')</syntaxhighlight>

Similar to the Ruby implementation, this will read up to the first 7 lines, returning only the last. Note that the 'readlines' method reads the entire file contents into memory first as opposed to using the file iterator itself which is more performant for large files.

<~~lang~~ python>

print open('xxx.txt').readlines()[:7][-1]

</syntaxhighlight>

</lang>

=={{header|R}}==

<~~lang~~ R>> seven <- scan('hw.txt', '', skip = 6, nlines = 1, sep = '\n') # too short

<syntaxhighlight lang="r">> seven <- scan('hw.txt', '', skip = 6, nlines = 1, sep = '\n') # too short

Read 0 items

> seven <- scan('Incoming/quotes.txt', '', skip = 6, nlines = 1, sep = '\n')

Read 1 item

</syntaxhighlight>

</lang>

=={{header|Racket}}==

#lang racket

Line 1,819:

(call-with-input-file "some-file"

(λ(i) (for/last ([line (in-lines i)] [n 7]) line))))

</syntaxhighlight>

</lang>

=={{header|Raku}}==

(formerly Perl 6)

<lang ~~perl6~~>say lines[6] // die "Short file";</~~lang~~>

<syntaxhighlight lang="raku" line>say lines[6] // die "Short file";</syntaxhighlight>

Without an argument, the <tt>lines</tt> function reads filenames from the command line, or defaults to standard input. It then returns a lazy list, which we subscript to get the 7th element. Assuming this code is in a program called <tt>line7</tt>:

<pre>$ cal 2011 > cal.txt

Line 1,836:

=={{header|REBOL}}==

<~~lang~~ rebol>

x: pick read/lines request-file/only 7

either x [print x] [print "No seventh line"]

</syntaxhighlight>

</lang>

=={{header|Red}}==

<~~lang~~ ~~Red~~>>> x: pick read/lines %file.txt 7

<syntaxhighlight lang="red">>> x: pick read/lines %file.txt 7

case [

Line 1,848:

(length? x) = 0 [print "Line 7 is empty"]

(length? x) > 0 [print append "Line seven = " x]

]</~~lang~~>

]</syntaxhighlight>

=={{header|REXX}}==

===for newer REXXes===

<~~lang~~ ~~REXX~~>/*REXX program reads a specific line from a file (and displays the length and content).*/

<syntaxhighlight lang="rexx">/*REXX program reads a specific line from a file (and displays the length and content).*/

parse arg FID n . /*obtain optional arguments from the CL*/

if FID=='' | FID=="," then FID= 'JUNK.TXT' /*not specified? Then use the default.*/

Line 1,869:

exit /*stick a fork in it, we're all done. */

/*──────────────────────────────────────────────────────────────────────────────────────*/

ser: say; say '***error!*** File ' FID " " arg(1); say; exit 13</~~lang~~>

ser: say; say '***error!*** File ' FID " " arg(1); say; exit 13</syntaxhighlight>

===for older REXXes===

Some older REXXes don't support a 2nd argument for the   '''linein'''   BIF, so here is an alternative:

<~~lang~~ ~~REXX~~>/*REXX program reads a specific line from a file (and displays the length and content).*/

<syntaxhighlight lang="rexx">/*REXX program reads a specific line from a file (and displays the length and content).*/

parse arg FID n . /*obtain optional arguments from the CL*/

if FID=='' | FID=="," then FID= 'JUNK.TXT' /*not specified? Then use the default.*/

Line 1,893:

exit /*stick a fork in it, we're all done. */

/*──────────────────────────────────────────────────────────────────────────────────────*/

ser: say; say '***error!*** File ' FID " " arg(1); say; exit 13</~~lang~~>

ser: say; say '***error!*** File ' FID " " arg(1); say; exit 13</syntaxhighlight>

=={{header|Ring}}==

<~~lang~~ ring>

fp = fopen("C:\Ring\ReadMe.txt","r")

n = 0

Line 1,910:

end

fclose(fp)

</syntaxhighlight>

</lang>

=={{header|Ruby}}==

The each_line method returns an Enumerator, so no more than seven lines are read.

<~~lang~~ ruby> seventh_line = open("/etc/passwd").each_line.take(7).last

<syntaxhighlight lang="ruby"> seventh_line = open("/etc/passwd").each_line.take(7).last

</syntaxhighlight>

</lang>

=={{header|Run BASIC}}==

<~~lang~~ runbasic>fileName$ = "f:\sample.txt"

<syntaxhighlight lang="runbasic">fileName$ = "f:\sample.txt"

requiredLine = 7

open fileName$ for input as #f

Line 1,927:

close #f

print a$

end</~~lang~~>

end</syntaxhighlight>

=={{header|Rust}}==

<~~lang~~ rust>use std::fs::File;

<syntaxhighlight lang="rust">use std::fs::File;

use std::io::BufRead;

use std::io::BufReader;

Line 1,948:

let mut lines = content.lines();

lines.nth(line_num).expect("No line found at that position")

}</~~lang~~>

}</syntaxhighlight>

Alternate implementation with argument parsing. First argument is the path to the file and is required. Second argument is the line number and is optional. By default the first line will be printed.

<~~lang~~ rust>use std::env;

<syntaxhighlight lang="rust">use std::env;

use std::fs::File;

use std::io::BufRead;

Line 1,982:

let line = lines.nth(line_num).expect("No line found at given position");

println!("{}", line.expect("None line"));

}</~~lang~~>

}</syntaxhighlight>

=={{header|Scala}}==

Line 1,988:

The code will throw a <tt>NoSuchElementException</tt> if the file doesn't have 7 lines.

<~~lang~~ scala>val lines = io.Source.fromFile("input.txt").getLines

<syntaxhighlight lang="scala">val lines = io.Source.fromFile("input.txt").getLines

val seventhLine = lines drop(6) next</~~lang~~>

val seventhLine = lines drop(6) next</syntaxhighlight>

===Imperative version===

Solving the task to the letter, imperative version:

<~~lang~~ scala>var lines: Iterator[String] = _

<syntaxhighlight lang="scala">var lines: Iterator[String] = _

try {

lines = io.Source.fromFile("input.txt").getLines drop(6)

Line 2,005:

else seventhLine = lines next

}

if ("" == seventhLine) println("line is empty")</~~lang~~>

if ("" == seventhLine) println("line is empty")</syntaxhighlight>

===Functional version (Recommanded)===

<~~lang~~ scala>val file = try Left(io.Source.fromFile("input.txt")) catch {

<syntaxhighlight lang="scala">val file = try Left(io.Source.fromFile("input.txt")) catch {

case exc => Right(exc.getMessage)

}

val seventhLine = (for(f <- file.left;

line <- f.getLines.toStream.drop(6).headOption.toLeft("too few lines").left) yield

if (line == "") Right("line is empty") else Left(line)).joinLeft</~~lang~~>

if (line == "") Right("line is empty") else Left(line)).joinLeft</syntaxhighlight>

=={{header|sed}}==

To print the seventh line:

To print an error message, if no such line:

<~~lang~~ sed>sed '7h;$!d;x;s/^$/Error: no such line/'</~~lang~~>

<syntaxhighlight lang="sed">sed '7h;$!d;x;s/^$/Error: no such line/'</syntaxhighlight>

That is we remember (h) the line, if any, in hold space. At the last line ($) we exchange (x) pattern space and hold space. If the hold space was empty, replace it by an error message. (Does not work with empty input, because there is no last line.)

Line 2,025:

and reads the requested line with [http://seed7.sourceforge.net/libraries/file.htm#getln%28inout_file%29 getln] afterwards:

<~~lang~~ seed7>$ include "seed7_05.s7i";

<syntaxhighlight lang="seed7">$ include "seed7_05.s7i";

const func string: getLine (inout file: aFile, in var integer: lineNum) is func

Line 2,056:

end if;

end func;</~~lang~~>

end func;</syntaxhighlight>

=={{header|SenseTalk}}==

SenseTalk's chunk expressions and ability to treat a file directly as a container make this trivial. If the file has fewer than 7 lines, theLine will be empty.

<~~lang~~ sensetalk>put line 7 of file "example.txt" into theLine

<syntaxhighlight lang="sensetalk">put line 7 of file "example.txt" into theLine

</syntaxhighlight>

</lang>

=={{header|Sidef}}==

<~~lang~~ ruby>func getNthLine(filename, n) {

<syntaxhighlight lang="ruby">func getNthLine(filename, n) {

var file = File.new(filename);

file.open_r.each { |line|

Line 2,074:

var line = getNthLine("/etc/passwd", 7);

print line if defined line;</~~lang~~>

print line if defined line;</syntaxhighlight>

=={{header|Smalltalk}}==

<~~lang~~ smalltalk>

line := (StandardFileStream oldFileNamed: 'test.txt') contents lineNumber: 7.

</syntaxhighlight>

</lang>

=={{header|SPL}}==

<~~lang~~ spl>lines = #.readlines("test.txt")

<syntaxhighlight lang="spl">lines = #.readlines("test.txt")

#.output("Seventh line of text:")

? #.size(lines,1)<7

Line 2,088:

!

#.output(lines[7])

.</~~lang~~>

.</syntaxhighlight>

=={{header|Stata}}==

See '''[http://www.stata.com/help.cgi?use use]''' in Stata help, to load a dataset or a part of it.

<~~lang~~ stata>* Read rows 20 to 30 from somedata.dta

<syntaxhighlight lang="stata">* Read rows 20 to 30 from somedata.dta

. use somedata in 20/30, clear

* Read rows for which the variable x is positive

. use somedata if x>0, clear</~~lang~~>

. use somedata if x>0, clear</syntaxhighlight>

If there are not enough lines, an error message is print. It's possible to '''[http://www.stata.com/help.cgi?capture capture]''' the error and do something else:

<~~lang~~ stata>capture use somedata in 7, clear

<syntaxhighlight lang="stata">capture use somedata in 7, clear

if _rc {

display "Too few lines"

}</~~lang~~>

}</syntaxhighlight>

=={{header|Tcl}}==

This code can deal with very large files with very long lines (up to 1 billion characters in a line should work fine, provided enough memory is available) and will return an empty string when the ''n''th line is empty (as an empty line is still a valid line).

<~~lang~~ tcl>proc getNthLineFromFile {filename n} {

<syntaxhighlight lang="tcl">proc getNthLineFromFile {filename n} {

set f [open $filename]

while {[incr n -1] > 0} {

Line 2,120:

}

puts [getNthLineFromFile example.txt 7]</~~lang~~>

puts [getNthLineFromFile example.txt 7]</syntaxhighlight>

Where it is necessary to provide very fast access to lines of text, it becomes sensible to create an index file describing the locations of the starts of lines so that the reader code can <code>seek</code> directly to the right location. This is rarely needed, but can occasionally be helpful.

Line 2,152:

=={{header|TUSCRIPT}}==

<~~lang~~ tuscript>$$ MODE TUSCRIPT

<syntaxhighlight lang="tuscript">$$ MODE TUSCRIPT

file="lines.txt"

ERROR/STOP OPEN (file,READ,-std-)

line2fetch=7</~~lang~~>

line2fetch=7</syntaxhighlight>

=={{header|TXR}}==

===From the top===

Variable "line" matches and takes eighth line of input:

<~~lang~~ txr>@(skip nil 7)

<syntaxhighlight lang="txr">@(skip nil 7)

@line</~~lang~~>

@line</syntaxhighlight>

===From the bottom===

Take the third line from the bottom of the file, if it exists.

<~~lang~~ txr>@(skip)

<syntaxhighlight lang="txr">@(skip)

@line

@(skip 1 2)

@(eof)</~~lang~~>

@(eof)</syntaxhighlight>

How this works is that the first <code>skip</code> will skip enough lines until the rest of the query successfully matches the input. The rest of the query matches a line, then skips two lines, and matches on EOF. So <code>@line</code> can only match at one location: three lines up from the end of the file. If the file doesn't have at least three lines, the query fails.

Line 2,174:

<~~lang~~ bash>get_nth_line() {

<syntaxhighlight lang="bash">get_nth_line() {

local file=$1 n=$2 line

while ((n-- > 0)); do

Line 2,185:

}

get_nth_line filename 7</~~lang~~>

get_nth_line filename 7</syntaxhighlight>

You can also use standard tools instead of built-ins:.

<~~lang~~ bash>awk NR==7 filename

<syntaxhighlight lang="bash">awk NR==7 filename

sed -n 7p filename

head -n 7 filename | tail -n 1</~~lang~~>

head -n 7 filename | tail -n 1</syntaxhighlight>

=={{header|Ursa}}==

<~~lang~~ ursa>decl string<> lines

<syntaxhighlight lang="ursa">decl string<> lines

decl file f

f.open "filename.txt"

Line 2,206:

out "the seventh line in the file is:" endl endl console

out lines<6> endl console</~~lang~~>

out lines<6> endl console</syntaxhighlight>

=={{header|VBScript}}==

Function read_line(filepath,n)

Set objFSO = CreateObject("Scripting.FileSystemObject")

Line 2,228:

WScript.Echo read_line("c:\temp\input.txt",7)

</syntaxhighlight>

</lang>

Line 2,248:

This example reads the 7th line (including newline character(s)) into text register 10.

<~~lang~~ vedit>File_Open("example.txt", BROWSE)

<syntaxhighlight lang="vedit">File_Open("example.txt", BROWSE)

Goto_Line(7)

if (Cur_Line < 7) {

Line 2,258:

Reg_Copy(10, 1)

}

Buf_Close(NOMSG) </~~lang~~>

Buf_Close(NOMSG) </syntaxhighlight>

If the file does not exist, the buffer will be empty and you get "File contains too few lines" error.

Line 2,267:

=={{header|Wren}}==

<~~lang~~ ecmascript>import "io" for File

<syntaxhighlight lang="ecmascript">import "io" for File

var lines = File.read("input.txt").replace("\r", "").split("\n")

Line 2,290:

Line 7

Line 8

*/</~~lang~~>

*/</syntaxhighlight>

Line 2,301:

Usage: readline <filename.ext

<~~lang~~ ~~XPL0~~>include c:\cxpl\codes; \intrinsic 'code' declarations

<syntaxhighlight lang="xpl0">include c:\cxpl\codes; \intrinsic 'code' declarations

def MaxLen = 82; \maximum length of line that can be stored (incl CR+LF)

Line 2,326:

char LineN(MaxLen);

if ReadLine(7, LineN) then Text(0, LineN)</~~lang~~>

if ReadLine(7, LineN) then Text(0, LineN)</syntaxhighlight>

=={{header|zkl}}==

Many zkl sequence objects contain a readln method, some contain a seek (or equivalent) method. However, File only has readln. If, for some, reason, the nth line can't be read, an exception is thrown.

<~~lang~~ zkl>reg line; do(7){line=File.stdin.readln()} println(">>>",line);</~~lang~~>

<syntaxhighlight lang="zkl">reg line; do(7){line=File.stdin.readln()} println(">>>",line);</syntaxhighlight>

Or, suck in lines and take the last one:

<~~lang~~ zkl>lines:=File.stdin.readln(7); println(">>>",line[-1]);</~~lang~~>

<syntaxhighlight lang="zkl">lines:=File.stdin.readln(7); println(">>>",line[-1]);</syntaxhighlight>