Parse value between two strings in bash

Question

I am pretty newe to linux and even though I need something simple I dont know where to start. In a bash script I need to parse the value from a HTML page between the string "VOL. " and "," and pass it to a variable.

score 4 · Accepted Answer · edited May 23 '17 at 12:06

4

newvar=$(grep -oP 'VOL\.\K.*?(?=,)' file.txt)
echo "$newvar"

or from a string :

newvar=$(grep -oP 'VOL\.\K.*?(?=,)' <<< "$string")
echo "$newvar"

if you need something more portable :

newvar=$(perl -lne '/VOL\.\K.*?(?=,)/ && print $&' <<< "$string")
echo "$newvar"

Explanations of the Regex

VOL\. = literal VOL. : the . = any character in regex without backslash
\K = restart the match to zero, see https://stackoverflow.com/a/13543042/465183
.*? = any character, 0 to N occurrences but non-greedy with ? char
(?=,) = it's a positive look-ahead assertion to look up the , char

edited May 23 '17 at 12:06

Community

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answered Apr 20 '13 at 15:01

Gilles Quénot

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Note that `-P` is a gnu flag and not available on most non-Linux systems, e.g. Macs and other BSDs. – Kevin Apr 20 '13 at 15:15
Yes, but OP have `linux` tag ;) – Gilles Quénot Apr 20 '13 at 17:12
Anyway, added a more portable `perl` solution. – Gilles Quénot Apr 20 '13 at 17:13
Thanks sputnick, that works. Just for the sake of understanding it is 'VOL\.\K.*?(?=,)' regex? Because I tried to make this expressions works with no success: (?<=VOL. )(.*)(?=,) – CptNemo Apr 20 '13 at 21:58

score 1 · Answer 2 · answered Apr 20 '13 at 17:00

1

This can be done using bash's built-in regex matching:

if [[ "$var" =~ "VOL. "([^,]*)"," ]]; then
    match="${BASH_REMATCH[1]}"
fi

answered Apr 20 '13 at 17:00

Gordon Davisson

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Parse value between two strings in bash

2 Answers2

Explanations of the Regex