CODEWITHSUNDEEP
stringbashshellunix
Joyita Tiwari
Joyita Tiwari

Reputation: 11

Compare two string variables in bash shell script

The output I get is sh21.sh: 5: [: xhi: unexpected operator no match

My code is as follows:

#!/bin/bash
s1="hi"
s2="hi"
s3="hello"
if [ "x$s1" == "x$s2" ]
then
  echo match
else
  echo no match
fi

Please explain to me what I am doing wrong.

Upvotes: 0

Views: 302

Answers (3)

David C. Rankin
David C. Rankin

Reputation: 84652

if [ "x$s1" == "x$s2" ]

should be

if [ "x$s1" = "x$s2" ]

There is only 1 equal sign when using test or [ in shell programming. Bash allows == with [[, but it should not be used with [. Both test and [ are equivalent and are the POSIX test utility. Bash has the [[ operator that is not the same. There are subtle differences in syntax, quoting requirements and available operators between them.

Upvotes: 2

John1024
John1024

Reputation: 113994

If you are going to use bashisms in your script, it is important to use bash. Your code works fine with bash:

$ bash sh21.sh
match

It fails with dash (which is the sh on debian-like systems):

$ sh sh21.sh
sh21.sh: 5: [: xhi: unexpected operator
no match

== is a bashism, meaning it only works under bash or similar shells. If you want a POSIX compatible script, use =. If not, run the script under bash.

Upvotes: 3

Feng
Feng

Reputation: 4048

Maybe you are using Debian based distros, and the default shell is dash, not bash

Check your shell

ls -l /bin/sh /bin/bash

Run the script with bash

bash sh21.sh

Upvotes: 0

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