How to truncate a string to a specific length in perl? - perl

Question

I am just unable to find "truncate a string to a specific length" in Perl.
Is there any built in way?
UPDATE:
input: $str = "abcd";
output (truncate for 3 characters): $str is abc

Answer 1

You want to use the substr() function.
$shortened = substr( $long, 0, 50 ); # 50 characters long, starting at the beginning.
For more, use perldoc
perldoc -f substr
In your case, it would be:
$str = 'abcd';
$short = substr( $str, 0, 3 );

Answer 2

For a string of arbitrary length, where truncate length can be longer than string length, I would opt for a substitution
$str =~ s/.{3}\K.*//s;
For shorter strings, the substitution will not match and the string will be unchanged. The convenient \K escape can be replaced with a lookbehind assertion, or a simple capture:
s/(?<=.{3}).*//s # lookbehind
s/(.{3}).*/$1/s # capture

Answer 3

It's probably useful to also mention that, instead of substr() or regular expressions, you could use printf or sprintf.
See perldoc -f sprintf :
For string conversions, specifying a precision truncates the string to
fit the specified width:
printf '<%.5s>', "truncated"; # prints "<trunc>"
printf '<%10.5s>', "truncated"; # prints "< trunc>"

Answer 4

As long as your original string is at least 3 characters long, you can use a call to substr as an lvalue.
my $str = "abcd";
substr($str, 3) = "";
print "$str\n"; # prints "abc"
The initial length of the string may need to be checked, as if it is shorter than 3 characters, the return value of this call to substr cannot be assigned to (see perldoc -f substr for more information) and attempting to do so will cause an error.

Answer 5

If I understand correctly, you need to do like php wordwrap() a string, so :
use Text::Format;
print Text::Format->new({columns => 50})->format($string);
If you just need the first N characters :
print substr $string, 0, 50;

Answer 6

Or you can use regexp to do the same.
#!/usr/bin/perl -w
use strict;
my $str = "abcd";
$str =~ /(\w{0,3})/;
print $1;

Answer 7

The most natural way is to use substr to extract the part you want:
$first_n = substr($string, 0, $n);
If you only want to modify the string and you are certain it is at least the desired length:
substr($string, $n) = '';
If you are not certain, you can do:
use List::Util "min";
substr($string, min($n, length($string))) = '';
or catch the exception:
eval { substr($string, $n) = '' };