How can I compare a string to multiple correct values in Bash?

Question

I have the following piece of Bash script:

function get_cms {
    echo "input cms name"
    read cms
    cms=${cms,,}
    if [ "$cms" != "wordpress" && "$cms" != "meganto" && "$cms" != "typo3" ]; then
        get_cms
    fi
}

But no matter what I input (correct and incorrect values), it never calls the function again, because I only want to allow 1 of those 3 inputs.

I have tried it with ||, with [ var != value ] or [ var != value1 ] or [ var != value1 ], but nothing works.

Can someone point me in the right direction?

@triplee I voted to reopen. I believe the other question stackoverflow.com/questions/22259259 should be closed instead. This question is more clearly forumulated, came sooner, and has better answers than the other. — studgeek
– studgeek, Commented Jun 6, 2020 at 16:44
The duplicate is better IMHO in that it has case as the accepted answer, but I guess this is mainly a matter of personal taste. Note that case is portable back to the original Bourne shell., and of course also to modern POSIX shell. Maybe see also Difference between sh and bash — tripleee
– tripleee, Commented Jun 6, 2020 at 18:00
Thanks. This one does have a case answer as well. It isn't the accepted one, but personally I always look at all the answers and their votes more then then which one is accepted (since the latter is just one person's opinion, while the votes are from many folks). — studgeek
– studgeek, Commented Jun 8, 2020 at 1:21

vvvvv · Accepted Answer · 2022-02-25 18:53:19Z

192

If the main intent is to check whether the supplied value is not found in a list, maybe you can use the extended regular expression matching built in BASH via the "equal tilde" operator (see also this answer):

if ! [[ "$cms" =~ ^(wordpress|meganto|typo3)$ ]]; then get_cms ; fi

edited Feb 25, 2022 at 18:53

vvvvv

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answered May 24, 2016 at 8:54

user3515756

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4 Comments

foob.ar Over a year ago

Extra points for the cleaner answer. I prefer putting the ! inside [[ ]] but both are equally valid.

maoyi Over a year ago

Thank you so much for this answer. Helped me to solve an issue at work!

Freedo Over a year ago

for some reason this doesn't work for me. I'm using (id=2015|id=2016) and I want the IF to execute if the variable has one of those strings anywhere, but it doesn't work

Kostas Tsiligkiris Over a year ago

If you want to check the string values to be anywhere in the variable, you should remove ^ and $, for example: if [[ "$id" =~ (2015|2016) ]]; then ......

Alfe · Accepted Answer · 2015-03-05 10:14:29Z

65

Maybe you should better use a case for such lists:

case "$cms" in
  wordpress|meganto|typo3)
    do_your_else_case
    ;;
  *)
    do_your_then_case
    ;;
esac

I think for long such lists this is better readable.

If you still prefer the if you can do it with single brackets in two ways:

if [ "$cms" != wordpress -a "$cms" != meganto -a "$cms" != typo3 ]; then

or

if [ "$cms" != wordpress ] && [ "$cms" != meganto ] && [ "$cms" != typo3 ]; then

edited Mar 5, 2015 at 10:14

answered Jan 16, 2014 at 9:26

Alfe

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8 Comments

Aquarius Power Over a year ago

it works great! btw, arent "do_your_then|else_case" text tip inverted? :)

Alfe Over a year ago

OP was formulating his original condition using ≠ (!=); my version with the case is matching (so it is rather using a comparison with =), hence the inversion.

Xiao Over a year ago

Beautiful solution. Are there any gotchas associated with using case like this?

Alfe Over a year ago

Shell programming is never free of "gotchas", as you put it ;-) I can think of problems using comparison strings with spaces or pipe symbols or other strange characters in them; in this case you would need to quote them properly. This would take time to find the right syntax and would at least be hard to read for the next maintainer of the code.

Charles Duffy Over a year ago

@Alfe, see the [OB XSI] notation in pubs.opengroup.org/onlinepubs/9699919799/utilities/test.html. If you click on it, it'll link you to a definition: The functionality described may be removed in a future version of this volume of POSIX.1-2008. Strictly Conforming POSIX Applications and Strictly Conforming XSI Applications shall not use obsolescent features. I doubt GNU coreutils or bash will actually remove it, but it is scheduled to in the future no longer be POSIX-mandated behavior (for good cause, given the ambiguities introduced).

|

devnull · Accepted Answer · 2014-01-16 09:07:39Z

58

Instead of saying:

if [ "$cms" != "wordpress" && "$cms" != "meganto" && "$cms" != "typo3" ]; then

say:

if [[ "$cms" != "wordpress" && "$cms" != "meganto" && "$cms" != "typo3" ]]; then

You might also want to refer to Conditional Constructs.

answered Jan 16, 2014 at 9:07

devnull

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2 Comments

Alfe Over a year ago

Repeating "$cms" != again and a again isn't very DRY. It leaves room for typos in any of the occasions (e. g. "$csm" !=), and you have no compiler to point that out to you in shells. Better try to avoid repeating the variable name. (See my answer for a way to do that.)

Gharbad The Weak Over a year ago

I had to remove the ; at the end so instead of being ... "typo3" ]]; then it is ..."typo3"]] then, but otherwise this worked just fine.

Abdull · Accepted Answer · 2023-08-31 12:53:47Z

19

As @Renich suggests, you can also use extended globbing for pattern matching. So you can use the same patterns you use to match files in command arguments (e.g. ls *.pdf) inside of bash comparisons.

For your particular case you can do the following.

if [[ "${cms}" != @(wordpress|magento|typo3) ]]

The @ means "Matches one of the given patterns". So this is basically saying cms is not equal to 'wordpress' OR 'magento' OR 'typo3'. In normal regular expression syntax @ is similar to just ^(wordpress|magento|typo3)$.

Mitch Frazier has two good articles in the Linux Journal on this Pattern Matching In Bash and Bash Extended Globbing.

For more background on extended globbing see Pattern Matching (Bash Reference Manual).

edited Aug 31, 2023 at 12:53

Abdull

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answered Jun 8, 2020 at 1:41

studgeek

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Comments

Renich · Accepted Answer · 2021-07-21 15:23:27Z

9

Here's my solution

if [[ "${cms}" != @(wordpress|magento|typo3) ]]; then

edited Jul 21, 2021 at 15:23

answered Feb 6, 2015 at 0:09

Renich

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2 Comments

gniourf_gniourf Over a year ago

Not + but @ in your extglob. Otherwise you'll get wrong results for, e.g., wordpressmagento or typo3typo3.

Jesse Nickles Over a year ago

@gniourf_gniourf I believe Edgar Grill answer is the same problem using ^ can result in matching any result that begins with "wordpress..." etc.

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