How to represent multiple conditions in a shell if statement?

Question

I want to represent multiple conditions like this:

if [ ( $g -eq 1 -a "$c" = "123" ) -o ( $g -eq 2 -a "$c" = "456" ) ]   
then  
    echo abc;  
else  
    echo efg;   
fi

but when I execute the script, it shows

syntax error at line 15: `[' unexpected,

where line 15 is the one showing if ....

What is wrong with this condition? I guess something is wrong with the ().

You are not asking about shell conditions but [test](https://de.wikipedia.org/wiki/Test_%28Unix%29) conditions. The whole expression in your example is evaluated by `test` (`[`) and not by the shell. The shell evaluates just the exit status of `[`. — ceving, Jun 17 '15 at 13:06
See also http://stackoverflow.com/questions/16203088/multiple-conditions-if-statement-bash-script — tripleee, Dec 15 '15 at 09:08
Related: [Compound if statements with multiple expressions in Bash](https://stackoverflow.com/q/11267569/6862601) — codeforester, Aug 15 '19 at 20:10

Jonathan Leffler · Accepted Answer · 2015-05-03T15:43:01.363

Classic technique (escape metacharacters):

if [ \( "$g" -eq 1 -a "$c" = "123" \) -o \( "$g" -eq 2 -a "$c" = "456" \) ]
then echo abc
else echo efg
fi

I've enclosed the references to $g in double quotes; that's good practice, in general. Strictly, the parentheses aren't needed because the precedence of -a and -o makes it correct even without them.

Note that the -a and -o operators are part of the POSIX specification for test, aka [, mainly for backwards compatibility (since they were a part of test in 7th Edition UNIX, for example), but they are explicitly marked as 'obsolescent' by POSIX. Bash (see conditional expressions) seems to preempt the classic and POSIX meanings for -a and -o with its own alternative operators that take arguments.

With some care, you can use the more modern [[ operator, but be aware that the versions in Bash and Korn Shell (for example) need not be identical.

for g in 1 2 3
do
    for c in 123 456 789
    do
        if [[ ( "$g" -eq 1 && "$c" = "123" ) || ( "$g" -eq 2 && "$c" = "456" ) ]]
        then echo "g = $g; c = $c; true"
        else echo "g = $g; c = $c; false"
        fi
    done
done

Example run, using Bash 3.2.57 on Mac OS X:

g = 1; c = 123; true
g = 1; c = 456; false
g = 1; c = 789; false
g = 2; c = 123; false
g = 2; c = 456; true
g = 2; c = 789; false
g = 3; c = 123; false
g = 3; c = 456; false
g = 3; c = 789; false

You don't need to quote the variables in [[ as you do with [ because it is not a separate command in the same way that [ is.

Isn't it a classic question?

I would have thought so. However, there is another alternative, namely:

if [ "$g" -eq 1 -a "$c" = "123" ] || [ "$g" -eq 2 -a "$c" = "456" ]
then echo abc
else echo efg
fi

Indeed, if you read the 'portable shell' guidelines for the autoconf tool or related packages, this notation — using '||' and '&&' — is what they recommend. I suppose you could even go so far as:

if [ "$g" -eq 1 ] && [ "$c" = "123" ]
then echo abc
elif [ "$g" -eq 2 ] && [ "$c" = "456" ]
then echo abc
else echo efg
fi

Where the actions are as trivial as echoing, this isn't bad. When the action block to be repeated is multiple lines, the repetition is too painful and one of the earlier versions is preferable — or you need to wrap the actions into a function that is invoked in the different then blocks.

It's good to know that escaped parentheses work; as an aside: in this particular case, the parentheses aren't even needed, because `-a` actually has higher precedence than `-o` (unlike `&&` and `||` in the shell - however, _inside_ `bash` `[[ ... ]]` _conditionals_, `&&` _also_ has higher precedence than `||` ). If you wanted to avoid `-a` and `-o` for maximum robustness and portability - which the [POSIX man page itself](http://man.cx/test) suggests - you could also use _subshells_ for grouping: `if ([ $g -eq 1 ] && [ "$c" = "123" ]) || ([ $g -eq 2 ] && [ "$c" = "456" ])` — mklement0, May 09 '14 at 12:11
Good solution, but I like the form without all the parenthesis and brackets: `if test "$g" -eq 1 -a "$c" = "123" || test "$g" -eq 2 -a "$c" = "456"; then ...` — Mogens TrasherDK, Mar 17 '18 at 07:06
I'm a bit late to this, but it's still a top search result, so I'd just like to note that using `&&` or `||` are also preferable as it behaves more like conditionals in other languages, and lets you short circuit conditions. For example: `if [ -n "${check_inodes}" ] && [ "$(stat -f %i "/foo/bar")" = "$(stat -f %i "/foo/baz")" ]`. Doing it this way, if `check_inodes` is empty, you avoid two calls to `stat`, whereas a larger, complex test condition must process *all* arguments before executing (which can also lead to bugs if you forget about that behaviour). — Haravikk, Apr 09 '20 at 10:52
For anyone having further trouble making this work, ensure there are spaces between your conditions and the parentheses too. — Simon, Jan 12 '23 at 11:06

score 226 · Answer 2 · answered Sep 29 '10 at 23:46

226

In Bash:

if [[ ( $g == 1 && $c == 123 ) || ( $g == 2 && $c == 456 ) ]]

answered Sep 29 '10 at 23:46

Dennis Williamson

346,391
90
374
439

12

Definitely the best approach in `bash`. As an aside: in this particular case the parentheses aren't even needed, because _inside_ `[[ ... ]]` _conditionals_ `&&` actually has higher precedence than `||` - unlike _outside_ such conditionals. – mklement0 May 09 '14 at 12:16
Is there a way we can find out which condition matched here? Was it the one in first parenthesis or the other one? – user47 Dec 11 '15 at 19:17
1

@Firelord: You'd need to separate the conditions into an `if` / `else` statement and have the code between `then` and `fi` put in a function in order to avoid repeating it. In very simple cases you could use a `case` statement with `;&` fallthrough (in Bash 4). – Dennis Williamson Dec 11 '15 at 22:15
3

Whats the purpose of the two square brackets? – Peter Chaula Apr 06 '17 at 08:10
4

@peter: Please see my answer [here](http://stackoverflow.com/a/2188369/26428), [Conditional Constructs in the Bash Manual](https://www.gnu.org/software/bash/manual/html_node/Conditional-Constructs.html#Conditional-Constructs) and [BashFAQ/31](http://mywiki.wooledge.org/BashFAQ/031). – Dennis Williamson Apr 06 '17 at 16:43
@DennisWilliamson thank You a lot, it helped me with diff-friendly formatting `if` statement conditions, moving each OR statement to separate line – Hunter_71 Jul 30 '18 at 09:26

score 52 · Answer 3 · edited Sep 23 '16 at 12:12

52

Using /bin/bash the following will work:

if [ "$option" = "Y" ] || [ "$option" = "y" ]; then
    echo "Entered $option"
fi

edited Sep 23 '16 at 12:12

David Ferenczy Rogožan

23,966
9
79
68

answered Jan 21 '15 at 10:23

sunitha

1,468
14
18

orkoden · Answer 4 · 2015-11-12T10:29:35.027

11

Be careful if you have spaces in your string variables and you check for existence. Be sure to quote them properly.

if [ ! "${somepath}" ] || [ ! "${otherstring}" ] || [ ! "${barstring}" ] ; then

edited Nov 12 '15 at 10:29

answered Nov 15 '13 at 17:40

orkoden

18,946
4
59
50

2

when we use the curly brackets after dollar symbol !! – Indrajeet Gour Sep 26 '15 at 18:52

score 8 · Answer 5 · edited Jan 26 '22 at 19:15

8

In Bash, you can use the following technique for string comparison

if [ $var OP "val" ]; then
    echo "statements"
fi

Example:

var="something"
if [ $var != "otherthing" ] && [ $var != "everything" ] && [ $var != "allthings" ]; then
    echo "this will be printed"
else
    echo "this will not be printed"
fi

edited Jan 26 '22 at 19:15

Peter Mortensen

30,738
21
105
131

answered Oct 14 '19 at 08:31

Ashan Priyadarshana

3,119
3
29
34

score 6 · Answer 6 · edited Jan 26 '22 at 19:13

6

g=3
c=133
([ "$g$c" = "1123" ] || [ "$g$c" = "2456" ]) && echo "abc" || echo "efg"

Output:

efg

g=1
c=123
([ "$g$c" = "1123" ] || [ "$g$c" = "2456" ]) && echo "abc" || echo "efg"

Output:

abc

edited Jan 26 '22 at 19:13

Peter Mortensen

30,738
21
105
131

answered Sep 30 '10 at 03:06

ghostdog74

327,991
56
259
343

2

That's a useless subshell. `{ ;}` could be used instead. – phk Sep 23 '16 at 16:40

score 0 · Answer 7 · edited May 04 '18 at 23:48

0

#!/bin/bash

current_usage=$( df -h | grep 'gfsvg-gfslv' | awk {'print $5'} )
echo $current_usage
critical_usage=6%
warning_usage=3%

if [[ ${current_usage%?} -lt ${warning_usage%?} ]]; then
echo OK current usage is $current_usage
elif [[ ${current_usage%?} -ge ${warning_usage%?} ]] && [[ ${current_usage%?} -lt ${critical_usage%?} ]]; then
echo Warning $current_usage
else
echo Critical $current_usage
fi

edited May 04 '18 at 23:48

Community

1
1

answered May 18 '17 at 11:43

Debjyoti Banerjee

1

5

Welcome to Stack Overflow! This question is looking for an *explanation*, not simply for working code. Your answer provides no insight for the questioner, and may be deleted. Please [edit] to explain what causes the observed symptoms. – Toby Speight May 18 '17 at 11:51

score -2 · Answer 8 · edited Jan 21 '22 at 14:26

-2

You can also chain more than two conditions:

if [ \( "$1" = '--usage' \) -o \( "$1" = '' \) -o \( "$1" = '--help' \) ]
then
   printf "\033[2J";printf "\033[0;0H"
   cat << EOF_PRINT_USAGE

   $0 - Purpose: upsert qto http json data to postgres db

   USAGE EXAMPLE:

   $0 -a foo -a bar



EOF_PRINT_USAGE
   exit 1
fi

edited Jan 21 '22 at 14:26

Peter Mortensen

30,738
21
105
131

answered May 24 '20 at 07:46

Yordan Georgiev

5,114
1
56
53

How to represent multiple conditions in a shell if statement?

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