Split a string by some separator in bash?

Question

I would like to split a string into substrings, separated by some separator (which is also a string itself).

How can I do that

• using bash only? (for minimalism, and my main interest)

• or If allowing some text processing program? (for convenience when the program is available)

Thanks.

Simple example,

• split 1--123--23 by -- into 1, 123 and 23.
• split 1?*123 by ?* into 1 and 123

Answer 1

Pure bash solution, using IFS and read. Note that the strings shouldn't contain $'\2' (or whatever else you use for IFS, unfortunately $'\0' doesn't work, but e.g. $'\666' does):

#!/bin/bash

split_by () {
    string=$1
    separator=$2

    tmp=${string//"$separator"/$'\2'}
    IFS=$'\2' read -a arr <<< "$tmp"
    for substr in "${arr[@]}" ; do
        echo "<$substr>"
    done
    echo
}


split_by '1--123--23' '--'
split_by '1?*123' '?*'

Or use Perl:

perl -E 'say for split quotemeta shift, shift' -- "$separator" "$string"

Answer 2

Simply with awk:

str="1--123--23"
awk -F'--' '{ for(i=1;i<=NF;i++) print $i }' <<< $str

The output:

1
123
23

---

Another short Python solution:

splitter.py script:

import sys
print('\n'.join(sys.argv[2].split(sys.argv[1])))

---

arguments order:

• sys.argv[0] - script name (i.e. splitter.py)

• sys.argv[1] - substring separator

• sys.argv[2] - input string

Usage:

python splitter.py "?*" "1?*123"
1
123

---

python splitter.py "--" "1--23--123"
1
23
123

Answer 3

Pure POSIX shell:

string="1--123--23"
del="--"

while test "${string#*$del}" != "$string" ; do
  echo "${string%%$del*}"
  string="${string#*$del}"
done
echo "$string"

Note that * or ? need to be escaped in the delimiter: del='\*'

Answer 4

#! /bin/bash
#  (GPL3+) Alberto Salvia Novella (es20490446e)


substring () {
    string=${1}
    separator=${2}
    position=${3}

    substring=${string//"${separator}"/$'\2'}
    IFS=$'\2' read -a substring <<< "${substring}"
    echo ${substring[${position}]}
}


substring ${@}

Answer 5

Similar to above but say you just want to get the URI for example:

URL="http://something.com/backup/v/photos/path/to/"
URI="./$(echo $URL | awk -F'.com/' '{print $2}')"
echo $URI

Answer 6

Using Raku (formerly known as Perl_6)

Briefly, split destructively removes a separator, which can be defined using a regex pattern:

~$ echo "string1_sep_string2" | raku -ne '.split(/ _sep_ /).put;'

Output:

string1 string2

You can also join after split-ting:

~$ echo "string1_sep_string2" | raku -ne '.split(/ _sep_ /).join(",").put;'

Output:

string1,string2

To look at the resultant elements one-per-line, iterate over the output with for. Adding perl or raku to the output call double-quotes the output, indicating that Raku understands the elements to be strings:

~$ echo "string1_sep_string2" | raku -ne '.raku.put for .split(/ _sep_ /);'

Output:

"string1"
"string2"

Note: you'll occasionally run into issues were empty strings remain after split-ting. These are removed by adding :skip-empty to the split call, as in .split(/ _sep_ /, :skip-empty)`. See examples below.

https://docs.raku.org/routine/split
https://raku.org