Find substring in shell script variable

Question

I have a string

$VAR="I-UAT";

in my shell script code. I need a conditional statement to check if "UAT" is present in that string.

What command should I use to get either true or false boolean as output? Or is there any other way of checking it?

Andrew Clark · Accepted Answer · 2011-07-26T16:06:40.940

25

What shell? Using bash:

if [[ "$VAR" =~ "UAT" ]]; then
    echo "matched"
else
    echo "didn't match"
fi

edited Jul 26 '11 at 16:06

answered Jul 25 '11 at 23:17

Andrew Clark

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6

Also, bash only, `[[ "$VAR" = *UAT* ]]` -- right hand side must be unquoted for pattern matching. – glenn jackman Jul 26 '11 at 01:18
pretty sure that's a bash only feature. Is your /bin/sh a symlink to bash? – glenn jackman Jul 26 '11 at 01:19
voted -1 because this answer is bash-specific while the `case`-based solutions will work on any POSIX shell. – adl Jul 26 '11 at 20:21
@adl - I guess I understand the logic there, but clearly the OP was using bash or my answer would not have been accepted. I would argue that you should edit the question so that it reflects the OP's intention, rather than downvote answers that are specific to a certain shell. – Andrew Clark Jul 26 '11 at 20:29
1

@Andrew - I too believe the OP uses bash, but since he did not mention it in the question we cannot be sure this is intentional. Maybe he simply does not know that many different shells have all sort of extensions that you should avoid if you want to write portable scripts. In that case he might later wonder why his script fails in other environments. Since there is an easy solution that is *portable*, I honestly believe it is best to avoid exotic features. – adl Jul 26 '11 at 20:46

score 9 · Answer 2 · answered Jul 25 '11 at 23:18

9

You can do it this way:

case "$VAR" in
  *UAT*)
   # code when var has UAT
  ;;
esac

answered Jul 25 '11 at 23:18

Diego Sevilla

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`case "$VAR" in` can always be replaced by `case $VAR in`. Shells do not perform *field splitting* or *pathname expansion* on the word that follows `case`. Similarly, `var="$other"` is as safe as `var=$other`. – adl Jul 26 '11 at 20:12

Jonathan Leffler · Answer 3 · 2011-07-26T23:40:50.510

6

The classic way, if you know ahead of time what string you're looking for, is a case statement:

case "$VAR" in
*UAT*) : OK;;
*)     : Oops;;
esac

You can use an appropriate command in place of the : command. This will work with Bourne and Korn shells too, not just with Bash.

edited Jul 26 '11 at 23:40

answered Jul 26 '11 at 00:53

Jonathan Leffler

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score 4 · Answer 4 · answered Jul 25 '11 at 23:20

4

found=`echo $VAR | grep -c UAT`

Then test for $found non-zero.

answered Jul 25 '11 at 23:20

jman

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This will also work. `-c, --count` Suppress normal output; instead print a count of matching lines for each input file. – Hari Ennekat Mar 03 '20 at 07:28

score 1 · Answer 5 · answered Jul 25 '11 at 23:16

1

In bash script you could use

if [ "$VAR" != "${VAR/UAT/}" ]; then
  # UAT present in $VAR
fi

answered Jul 25 '11 at 23:16

Neil

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score 1 · Answer 6 · edited May 05 '16 at 20:19

1

try with grep:

$ echo I\-UAT | grep UAT
$ echo $?
0
$ echo I\-UAT | grep UAX
$ echo $?
1

so testing

if [ $? -ne 0 ]; then
  # not found
else
  # found
fi

edited May 05 '16 at 20:19

vitalymak

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answered Jul 25 '11 at 23:16

marcelog

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Andy Alt · Answer 7 · 2022-09-30T03:19:02.060

0

I like this a little better than using case/esac (and it'll work with non-bash shells):

#!/bin/sh

full_string="I-UAT"
substring="UAT"

if [ -z "${full_string##*$substring*}" ]; then
        echo "Found substring!"
else
        echo "Substring is MIA!"
fi

If the string returned is zero-length (-z), then the substring was found.

edited Sep 30 '22 at 03:19

answered Sep 30 '22 at 03:11

Andy Alt

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Find substring in shell script variable

7 Answers7