File I/O in Perl

The modern open idiom: three arguments, a lexical handle, and or die.

use strict;
use warnings;

# three-arg open with a lexical filehandle
open my $out, ">", "notes.txt" or die "write: $!";
print {$out} "line $_\n" for 1 .. 3;
close $out;

open my $in, "<", "notes.txt" or die "read: $!";
while (my $line = <$in>) {
    chomp $line;
    print "read: $line\n";
}
close $in;

unlink "notes.txt" or die "unlink: $!";

How it works

1. Three-arg open splits mode from filename; or die $! reports failure.
2. print {$out} writes to the handle; a statement modifier loops three times.
3. while (<$in>) reads a line at a time and chomp trims the newline.
4. unlink deletes the scratch file so the run leaves nothing behind.

Keywords and builtins used here

• chomp
• close
• die
• for
• my
• open
• print
• unlink
• use
• while

The run, in numbers

Lines

16

Characters to type

336

Tokens

73

Three-star pace

75 tpm

At the three-star pace of 75 tokens a minute, this run takes about 58 seconds.

Type this snippet

Step 1 of 3 in Files & modern Perl, step 22 of 27 in Language basics.

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