Pattern to get string between two specific words/characters using grep

Question

I need to extract email address from a string like this (I'm making a log parser): <some text> from=someuser@somedomain.com, <some text>

with egrep (or grep -Eo). So the string needs to be pulled out only between "from=" and "," , because the other parts of log contain email addresses too, like to= and etc

Could you provide more sample text? – Shiplu Mokaddim Jan 12 '14 at 17:40 — Shiplu Mokaddim, Jan 12 '14 at 17:40

score 58 · Accepted Answer · answered Jan 12 '14 at 17:32

58

Using grep -oP:

s='<some text> from=someuser@somedomain.com, <some text>'
grep -oP '(?<=from=).*?(?=,)' <<< "$s"
someuser@somedomain.com

OR else avoid lookbehind by using \K:

grep -oP 'from=\K.*?(?=,)' <<< "$s"
someuser@somedomain.com

In case your grep doesn't support -P (PCRE) use this sed:

sed 's/.*from=\(.*\),.*/\1/' <<< "$s"
someuser@somedomain.com

answered Jan 12 '14 at 17:32

anubhava

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Thank you. It does exactly what i needed. I didn't know about -P option. Will save this example for future using as well – Shirker Jan 12 '14 at 18:54
1

This did exactly what I needed, thanks! – richddr Apr 20 '16 at 16:43
Will this work if the content to extract is spread over multiple lines (i.e. might contain one or more newlines)? – Mr. Developerdude Sep 20 '16 at 21:31
1

No, it won't match across the lines. You will need to use `grep -z` for that. – anubhava Sep 20 '16 at 21:33

score 29 · Answer 2 · edited Mar 05 '20 at 16:35

29

Try awk

echo '<text> from=someuser@somedomain.com, <text>' | awk -F[=,] '{print $2}'

Here $2 can be a different number based on its position.

Sample for word between symbols "(", ")":

echo "Linux Foundation Certified Engineer (LFCE-JP)" | awk -F[\(\)] '{print $2}'
LFCE-JP

edited Mar 05 '20 at 16:35

0x8BADF00D

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answered Jan 12 '14 at 17:39

Shiplu Mokaddim

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This one's better. – JohnAllen May 08 '16 at 02:30
3

I found this much easier to understand and use. – Digital Impermanence Aug 20 '16 at 13:33
1

You may need to escape for some special characters for e.g. () and doesn't work directly. Need to use awk -F[]. – Jitesh Sojitra Sep 23 '17 at 05:05
I had to escape even the back slash as following when I wanted string between two square brackets: `cat tmp.txt | awk -F[\\[\\]] '{print $2}'` – mvsagar Mar 18 '23 at 07:28

score 18 · Answer 3 · answered Nov 14 '17 at 06:31

A purely bash solution, requires two steps to strip prefix & suffix separately (but probably runs faster, because no subprocesses):

#!/bin/bash
orig='from=someuser@somedomain.com, <some text>'
one=${orig#*from=}
two=${one%,*}

printf "Result:\n"
printf "$orig\n"
printf "$one\n"
printf "$two\n"

Output:

Result:
from=someuser@somedomain.com, <some text>
someuser@somedomain.com, <some text>
someuser@somedomain.com

Notes:

${var#*pattern} using # strips from the start of $var up to pattern
${var%pattern*} using % strips from end of $var, up to pattern
similar could be accomplished with ${var/pattern/replace} (and leaving replace blank), but it's trickier since full regexp isn't supported (ie, can't use ^ or '$'), so you can't do (for example) /^from=//, but you could do in step one ${var/*from=/} and then in step two, do ${var/,*/} (depending on your data, of course).
see also: http://www.tldp.org/LDP/abs/html/parameter-substitution.html

This is elegant. it's approachable for newbie like me, and I can fully understand it after reading it. Thanks for your answer! — NeoZoom.lua, Jun 15 '22 at 14:52

Pattern to get string between two specific words/characters using grep

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