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 · 2011-07-26 16:06:40Z

26

What shell? Using bash:

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

edited Jul 26, 2011 at 16:06

answered Jul 25, 2011 at 23:17

Andrew Clark

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5 Comments

glenn jackman Over a year ago

Also, bash only, [[ "$VAR" = *UAT* ]] -- right hand side must be unquoted for pattern matching.

glenn jackman Over a year ago

pretty sure that's a bash only feature. Is your /bin/sh a symlink to bash?

adl Over a year ago

voted -1 because this answer is bash-specific while the case-based solutions will work on any POSIX shell.

Andrew Clark Over a year ago

@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.

adl Over a year ago

@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.

Diego Sevilla · Accepted Answer · 2011-07-25 23:18:26Z

9

You can do it this way:

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

answered Jul 25, 2011 at 23:18

Diego Sevilla

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1 Comment

adl Over a year ago

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.

Jonathan Leffler · Accepted Answer · 2011-07-26 23:40:50Z

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, 2011 at 23:40

answered Jul 26, 2011 at 0:53

Jonathan Leffler

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Comments

jman · Accepted Answer · 2011-07-25 23:20:02Z

4

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

Then test for $found non-zero.

answered Jul 25, 2011 at 23:20

jman

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1 Comment

Hari Ennekat Over a year ago

This will also work. -c, --count Suppress normal output; instead print a count of matching lines for each input file.

Neil · Accepted Answer · 2011-07-25 23:16:29Z

1

In bash script you could use

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

answered Jul 25, 2011 at 23:16

Neil

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Comments

vitalymak · Accepted Answer · 2016-05-05 20:19:50Z

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 5, 2016 at 20:19

vitalymak

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answered Jul 25, 2011 at 23:16

marcelog

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Comments

Andy Alt · Accepted Answer · 2022-09-30 03:19:02Z

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, 2022 at 3:19

answered Sep 30, 2022 at 3:11

Andy Alt

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