Finding substring of variable length in bash

Question

I have a string, such as time=1234, and I want to extract just the number after the = sign. However, this number could be in the range of 0 and 100000 (eg. - time=1, time=23, time=99999, etc.).

I've tried things like $(string:5:8}, but this will only work for examples of a certain length.

How do I get the substring of everything after the = sign? I would prefer to do it without outside commands like cut or awk, because I will be running this script on devices that may or may not have that functionality. I know there are examples out there using outside functions, but I am trying to find a solution without the use of such.

rstackhouse · Accepted Answer · 2024-02-13 17:58:30Z

6

s=time=1234
time_int=${s##*=}
echo "The content after the = in $s is $time_int"

This is a parameter expansion matching everything matching *= from the front of the variable -- thus, everything up to and including the last =.

If intending this to be non-greedy (that is, to remove only content up to the first = rather than the last =), use ${s#*=} -- a single # rather than two.

References:

edited Feb 13, 2024 at 17:58

rstackhouse

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answered Aug 2, 2016 at 19:24

Charles Duffy

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Fma · Accepted Answer · 2016-08-02 19:26:08Z

3

if time= part is constant you can remove prefix by using ${str#time=}

Let's say you have str='time=123123' if you execute echo ${str#time=} you would get 123123

edited Aug 2, 2016 at 19:26

answered Aug 2, 2016 at 19:24

Fma

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3 Comments

Charles Duffy Over a year ago

Since the OP is following best practices by using lower-case variable names, you might do the same.

Charles Duffy Over a year ago

...re: "best practices", see pubs.opengroup.org/onlinepubs/009695399/basedefs/…, defining conventions for naming of environment variables; since shell variables share a namespace (which is to say, for instance, that setting a shell variable named PATH will override the contents of the environment variable PATH), those conventions apply to shell variables as well.

Fma Over a year ago

Thanks updated as per your advice but the reason I used uppercase was so it wouldn't be confused with time= part :)

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