How do I write to a file?

vroom has asked for the wisdom of the Perl Monks concerning the following question: ⭐ (files)

Replies are listed 'Best First'.
Re: How do I write to a file?⭐ by revdiablo (Prior) on Jun 23, 2003 at 00:19 UTC
The 3-arg form of `open` is fairly useful to prevent problems with filenames "tricking" perl, and other nasty surprises: `open FH, ">", $outfile or die "Error writing '$outfile': $!\n"; print FH $output; close FH;` [download] Also useful are lexical filehandles: `open my $filehandle, ">", $outfile or die "Error writing '$outfile': $ +!\n"; print $filehandle $output; close $filehandle;` [download]	[reply] [d/l] [select]
Re: How do I write to a file?⭐ by devslashneil (Friar) on Jun 22, 2003 at 04:41 UTC
The Tie::File module can be used to bind an array to a file. Any changes you make to the array are then made retrospectivly to the file, without having to load the file into memory. This is especially useful for large files ex. `#!/usr/bin/perl use strict; use Tie::File; my @array; my $filename = 'foo.dat'; tie @array, 'Tie::File', $filename or die "Error: Cannot open $filenam +e\n"; push @array, "Hello, World!\n";` [download]	[reply] [d/l]
Re: How do I write to a file? by Crulx (Monk) on Jan 21, 2000 at 04:54 UTC
The open command opens a file. The first few characters of the second argument tell you how the file is opened. This code `open FH , ">$output_file";` [download] truncates and opens a file for writing. All the contents are lost. `open FH, ">>$output_file";` [download] Opens a file for appending. When you start writing to this file, it will write to the end. To actually WRITE to that file you use the print command `print FH "I will print this to a file\n";` [download]	[reply] [d/l] [select]
Re: How do I write to a file? by chromatic (Archbishop) on Mar 05, 2000 at 07:49 UTC
Always, ALWAYS check the return value of a command such as open: `open INPUT "myfile.txt" \|\| die "Cannot open file: $!";` This will save you hours of aggregate troubleshooting when your program fails silently. (The special variable $! contains the error message. Print it to discover why the file couldn't be opened.)	[reply] [d/l]
Re: Answer: How do I write to a file? by I0 (Priest) on Apr 08, 2002 at 06:22 UTC
`#I think you meant either open INPUT, "myfile.txt" or die "Cannot open file: $!"; #or (open INPUT, "myfile.txt") \|\| die "Cannot open file: $!"; #"myfile.txt" \|\| die "Cannot open file: $!" is always true` [download]	[reply] [d/l]
Re: How do I write to a file? by DigitalKitty (Parson) on Apr 07, 2002 at 22:11 UTC
A good idea when writing to a file is to include a space between the filename and the direction symbol. Like this: `open(FH, "> sample.txt") or die("Cannot write to file: $!\n");` [download] Perl will ignore the extra space between the '>' and the filename. It is useful in preventing unexpected results. -DigitalKitty	[reply] [d/l]
Re: How do I write to a file? by Mago (Parson) on Aug 07, 2003 at 00:16 UTC
`#!/usr/bin/perl use strict; use warnings; my $file = $ARGV[0]; my $line; open (FILE, "< $file"); while ($line = <FILE>) { chomp $line; printf("\n [$line]"); } close FILE;` [download]	[reply] [d/l]
Re: Answer: How do I write to a file? by ajdelore (Pilgrim) on Aug 07, 2003 at 18:30 UTC
Am I being dense here, or does this code read and print the file? The question asks how to write to the file. </ajdelore>	[reply]