Perl: Split string

Abstract: Split string using different patterns.

1. The function split()

The basic function for splitting strings in Perl is split(). The separated character is a space, and the output is an array.

my $s='ab d ge h';

my @arr=split / /, $s;

print join("\t", @arr), "\n";

The output:

ab d ge h

There are some other coding patterns depending requirements. The output array can be wrote as scalars:

$s='ab d, ge h';

my($a, $b)=split /,/, $s;

printf("%s, %s\n", $a, $b);

The output:

ab d, ge h

Or set the limits of number of splitted parts:

#assign to scalars and limit to two parts

$s='ab d ge h';

my($a, $b)=split / /, $s, 2;

printf("%s, %s\n", $a, $b);

The output:

ab, d ge h

2. Regular expression combined with split()

split a string according to one or more blank space:

#make slice

my $s = "1695 root 20 0 450148 135584 53660 S 4.3 0.4 96:29.74 Xorg";

my ($PID, $CPU) = (split /\s+/, $s)[0, 8];

printf("%s##%s\n", $PID, $CPU);

The output:

1695##4.3

Split a string by multiple characters:

my $s = 'fname=Foo&lname=Bar&email=foo@bar.com';

my @words = split /[=&]/, $r;

print join('_', @words), "\n";

The output:

fname_Foo_lname_Bar_email_foo@bar.com

Split string and reserve split pattern characters:

my $s='a-d-ge-h';

$s=~s/-/-@#%/g;

@arr= split /@#%/, $s;

print join(', ', @arr), "\n";

The output:

a-, d-, ge-, h

3.hanle DNA or protein sequences

Split a DNA sequence into nucleotides:

$s='ATTGTGCGCGGATGCAAACTCTAATC';

@arr=split //, $s;

print join("\t", @arr), "\n";

The output:

A T T G T G C G C G G A T G C A A A CTC T A A T C

Translate DNA sequence into amino acid sequence by splitting a string with 3 characters per piece;

@arr=split /(...)/, $s;

@arr=grep {/.+/} @arr; #then filter the empty entries

print '3 chr:', join(',', @arr), "\n";

The output:

3 chr:ATT,GTG,CGC,GGA,TGC,AAA,CTC,TAA,TC

Walk sequence and generate sequence stretches:

$s='MRSLLFVVGAWVAALVTNLTPDAALASGTTTTAAAGNT';

my $L=22;

my $step=2;

my @arr;

for(my $i; $i<length($s)-$L+$step; $i+=$step){

my $sub=substr($s, $i, $L);

push(@arr, $sub);

printf("%s%s\n", "--"x($i), $sub);

}

The output:

MRSLLFVVGAWVAALVTNLTPD

----SLLFVVGAWVAALVTNLTPDAA

--------LFVVGAWVAALVTNLTPDAALA

------------VVGAWVAALVTNLTPDAALASG

----------------GAWVAALVTNLTPDAALASGTT

--------------------WVAALVTNLTPDAALASGTTTT

------------------------AALVTNLTPDAALASGTTTTAA

----------------------------LVTNLTPDAALASGTTTTAAAG

--------------------------------TNLTPDAALASGTTTTAAAGNT