String comparison in bash. [[: not found

Question

I am trying to compare strings in bash. I already found an answer on how to do it on stackoverflow. In script I am trying, I am using the code submitted by Adam in the mentioned question:

#!/bin/bash
string='My string';

if [[ "$string" == *My* ]]
then
  echo "It's there!";
fi

needle='y s'
if [[ "$string" == *"$needle"* ]]; then
  echo "haystack '$string' contains needle '$needle'"
fi

I also tried approach from ubuntuforums that you can find in 2nd post

if [[ $var =~ regexp ]]; then
  #do something
fi

In both cases I receive error:

[[: not found

What am I doing wrong?

I might do it wrong, but using a single square bracket always worked for me. — Markus Unterwaditzer, Sep 01 '12 at 19:41
`[` won't work in this case, because it doesn't support patterns. — Ansgar Wiechers, Sep 01 '12 at 19:50

score 256 · Accepted Answer · edited Jul 23 '20 at 06:31

256

[[ is a bash-builtin. Your /bin/bash doesn't seem to be an actual bash.

From a comment:

Add #!/bin/bash at the top of file

edited Jul 23 '20 at 06:31

Abhay

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answered Sep 01 '12 at 19:27

Ansgar Wiechers

193,178
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if I type: type '[[' i get [[ is a shell keyword – user1581900 Sep 01 '12 at 19:32
5

Do you get the same result when you run `/bin/bash -c "type [["`? – Ansgar Wiechers Sep 01 '12 at 19:36
52

This happened to me because I forgot to add `#!/bin/bash` at the top of my file – morphatic Oct 29 '17 at 23:45
30

Happend to me because i ran the script with `sh`, lots for frustration. Now i just have to redo everything i undid before finding this answer. – Louis Loudog Trottier May 16 '18 at 05:01
1

I wish I could upvote you more... So much time lost. – Dan O'Boyle Sep 29 '20 at 01:24
Thank you! Just realised i'm an idiot. – Paul Danelli Oct 14 '21 at 21:10
It is really important that `#!/bin/bash` is on the 1st line. I generated a script that accidentally started with a new line which made this problem difficult to find. – cb2 Oct 06 '22 at 14:31

score 219 · Answer 2 · edited Jul 25 '16 at 23:53

219

How you are running your script? If you did with

$ sh myscript

you should try:

$ bash myscript

or, if the script is executable:

$ ./myscript

sh and bash are two different shells. While in the first case you are passing your script as an argument to the sh interpreter, in the second case you decide on the very first line which interpreter will be used.

edited Jul 25 '16 at 23:53

Fermin Silva

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answered Sep 01 '12 at 19:32

Akos K

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i got permission denied this way. with sudo ./myscript its command not found – user1581900 Sep 01 '12 at 19:37
11

do **chmod +x myscript**, then run again, you don't need sudo – Akos K Sep 01 '12 at 19:41
2

How you are invoking you script? – Akos K Sep 01 '12 at 19:48
like you said. normally i call it with '$sh myscipt.sh'. 2nd time after doing chmod +x myscript.sh i called it with ./myscript.sh – user1581900 Sep 01 '12 at 20:02
5

The error is expected when you run the script via `sh myscript.sh`, because `/bin/sh` emulates a Bourne shell where `[[` is not a builtin. However, running the script via `./script.sh` should not yield an error, because in that case the shebang should cause `/bin/bash` to be used. – Ansgar Wiechers Sep 01 '12 at 20:08
See also [Difference between `sh` and `bash`](/q//5725296) which elaborates on the differences. – tripleee Mar 05 '18 at 13:06

score 85 · Answer 3 · edited May 06 '13 at 17:02

85

Is the first line in your script:

#!/bin/bash

or

#!/bin/sh

the sh shell produces this error messages, not bash

edited May 06 '13 at 17:02

Kevin

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answered May 06 '13 at 16:58

Wiley

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First line was also missing for me producing the error the author mentioned! – Anonymous Nov 05 '15 at 10:49

score 28 · Answer 4 · edited Apr 27 '22 at 13:57

28

As @Ansgar mentioned, [[ is a bashism, ie built into Bash and not available for other shells. If you want your script to be portable, use [. Comparisons will also need a different syntax: change == to =.

if [ $MYVAR = "myvalue" ]; then
    echo "true"
else
    echo "false"
fi

edited Apr 27 '22 at 13:57

Etienne Gautier

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answered May 30 '16 at 14:55

Amedee Van Gasse

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101

Checked a bit with Ubuntu 16.04 and (sh ->) dash 0.5.8-2.1ubuntu2 and found that [ works fine in combination with "-eq" and alikes. Similar information on comparison operators for this context can be found here: https://stackoverflow.com/questions/10849297/compare-a-string-using-sh-shell - I further cheked with (( )) evaluation operator as recommended in the next link but that seemed to fail for my minimal invasive changes /or/ it would need a much deeper level of code changes. http://www.softpanorama.org/Scripting/Shellorama/Control_structures/comparison_operators.shtml – Alexander Stohr Jan 27 '20 at 08:00

score 17 · Answer 5 · answered Jul 19 '13 at 18:28

17

I had this problem when installing Heroku Toolbelt

This is how I solved the problem

$ ls -l /bin/sh
lrwxrwxrwx 1 root root 4 ago 15  2012 /bin/sh -> dash

As you can see, /bin/sh is a link to "dash" (not bash), and [[ is bash syntactic sugarness. So I just replaced the link to /bin/bash. Careful using rm like this in your system!

$ sudo rm /bin/sh
$ sudo ln -s /bin/bash /bin/sh

answered Jul 19 '13 at 18:28

jperelli

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Overriding the default `sh` for your distro is ill-advised IMHO. A shell which is run with `sh` should work with `dash`; if it doesn't, that's a bug in the script. If you need `bash` features, use `bash`, not `sh`. – tripleee Dec 15 '15 at 08:46
4

this sounds terrible tbh – MrVaykadji Mar 08 '16 at 03:10
2

I agree, it was just an ugly workaround. A similar but better workaround would be to use `update-alternatives` (in debian-based-linux) like this https://justinconover.wordpress.com/2012/05/14/ubuntu-changing-dash-to-bash/ but in the end, it would be the same. – jperelli Mar 08 '16 at 13:53

score 10 · Answer 6 · answered Sep 26 '20 at 15:31

10

If you know you're on bash, and still get this error, make sure you write the if with spaces.

[[1==1]] # This outputs error

[[ 1==1 ]] # OK

answered Sep 26 '20 at 15:31

Richard Miller

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score 4 · Answer 7 · answered Dec 13 '14 at 11:46

4

Specify bash instead of sh when running the script. I personally noticed they are different under ubuntu 12.10:

bash script.sh arg0 ... argn

answered Dec 13 '14 at 11:46

Smeterlink

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This fixed it for me! – Djamillah Jul 23 '15 at 18:45

score 3 · Answer 8 · answered May 31 '21 at 16:02

3

Execute in your terminal:

sudo update-alternatives --install /bin/sh sh /bin/bash 100

answered May 31 '21 at 16:02

Antonio Moreno

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score 0 · Answer 9 · answered Jan 22 '23 at 10:25

0

Make the file executable and then execute without sh.

make it executable by $ chmod +x filename
then instead of sh filename use ./filename

answered Jan 22 '23 at 10:25

Ashutosh Narayan Jha

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score 0 · Answer 10 · answered Jul 04 '23 at 09:42

0

I had the same error (on a Mac) – but due to the fact, that I entered a space before the "[" with the option key already down for typing the "[". So the space character was not the space character I wanted to type, but a "nonbreaking space". Not visible in the text editor – but caused a "[[ : command not found" error.

answered Jul 04 '23 at 09:42

CreaTurE

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This does not really answer the question. If you have a different question, you can ask it by clicking [Ask Question](https://stackoverflow.com/questions/ask). To get notified when this question gets new answers, you can [follow this question](https://meta.stackexchange.com/q/345661). Once you have enough [reputation](https://stackoverflow.com/help/whats-reputation), you can also [add a bounty](https://stackoverflow.com/help/privileges/set-bounties) to draw more attention to this question. - [From Review](/review/late-answers/34638384) – Yogendra Jul 07 '23 at 08:35

String comparison in bash. [[: not found

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