substring with bash and assign to a variable

Question

I execute the following command:

xinput  | grep Razer

the output is

⎜   ↳ Razer  Razer Abyssus                      id=12   [slave  pointer  (2)]

how can I get the id, assign it to a variable, so I can reuse it later in the script? The id is changing.

Graham · Accepted Answer · 2017-09-23 16:08:44Z

2

You can pipe your command to sed:

yourvar=$(xinput | sed '/Razer/s/.*id=\([0-9]*\).*/\1/')

/Razer/: when a line containing Razer is found
s/.*id=$[0-9]*$.*/\1/: capture the id value and print it using backreference.

edited Sep 23, 2017 at 16:08

Graham

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answered Jun 28, 2017 at 5:26

SLePort

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1 Comment

Micklos Over a year ago

Hi. I tried it... yourvar=$(xinput | sed '/Touchpad/s/.*id=([0-9]*).*/\1/') but when echoing $yourvar, the the whole result of xinput is given, and not just the number following the "id=" sub-string. I do have the following line in my xinput readout: ⎜ ↳ ELAN0518:01 04F3:31FC Touchpad id=11 [slave pointer (2)] I'm using bash 5.1.16 Any advice?

P.... · Accepted Answer · 2017-06-28 07:17:58Z

1

grep solution: Here if any line contains Razer followed by id then the ID is printed. Here perl regex is used by using -p flag of grep command. \K means ignore everything on left of it.

xinput  |grep -oP 'Razer.*id=\K[^ ]+'
12

Using gawk's match function:

awk '/Razer/{match($0,/id=([^ ]+)/,a);print a[1]}'
12

edited Jun 28, 2017 at 7:17

answered Jun 28, 2017 at 6:01

P....

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Comments

sjsam · Accepted Answer · 2017-06-28 08:38:36Z

0

if you've GNU AWK or gawk you can do the below too.

id=$(xinput | awk '/Razer/{printf "%s",gensub(/^.*id=[[:digit:]]*).*$/,"\\1",$0)}')

edited Jun 28, 2017 at 8:38

answered Jun 28, 2017 at 6:44

sjsam

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2 Comments

P.... Over a year ago

Hi do you want to change your regex to /^.*id=([[:digit:]]*).*$/ ?

sjsam Over a year ago

@PS : You're right, It so happened that the = got trimmed when I copied the command from my VM.

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