[SOLVED] extract substring with sed report error message

Issue

I would like to extract substring with sed as below:

#!/bin/bash
txt="[audio.sys.offload.pstimeout.secs]: [3]"
echo $txt|sed -r -e 's/\[[a-zA-Z0-9_.]+\].*/\1/'

expected output is:

audio.sys.offload.pstimeout.secs

Error message:

sed: -e expression #1, char 26: invalid reference \1 on `s' command's RHS

Solution

#!/bin/bash
txt="[audio.sys.offload.pstimeout.secs]: [3]"
echo $txt | sed -r -e 's/^\[(.*)\]:.*/\1/'

we're grabbing all the characters from the 1st [ until the last ]: and putting them in a capture group.

Would you like the regex to remain mostly like yours?

by the way - with lazy matching (which isn't supported by sed), the regex could be cleaner, simply ^\[(.*?\])

Answered By - Yarin_007

Answer Checked By - Mary Flores (WPSolving Volunteer)