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I have a bash script which checks if the ACCESS_TOKEN is equal to null it will exit.

ACCESS_TOKEN=$(jq -r '.access_token' <<<"$(curl --request GET \
  --url 'https://'$LANDSCAPE'/oauth/token/?grant_type=client_credentials' \
  -u "$CLIENT_ID":"$CLIENT_SECRET")")
if [[ -n $ACCESS_TOKEN -eq null ]]; then 
   exit 1
fi

or:

ACCESS_TOKEN=$(jq -r '.access_token' <<<"$(curl --request GET \
  --url 'https://'$LANDSCAPE'/oauth/token/?grant_type=client_credentials' \
  -u "$CLIENT_ID":"$CLIENT_SECRET")")
if [ -n "$ACCESS_TOKEN" -eq null ]; then 
   exit 1
fi

the console logs:

+ ACCESS_TOKEN=null
+ '[' -n null -eq null ']'
/tmp/jenkins6798373284183556496.sh: line 8: [: too many arguments

It seems that the if condition is not working well.

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1
  • Hard to guess what you're doing. What you posted has 6 lines, the error message states error on line 8? Commented Dec 9, 2018 at 20:51

3 Answers 3

Reset to default
3

If you want to check if the string is not empty and if it is "null", a better syntax is:

if [ -n "$ACCESS_TOKEN" ] && [ "$ACCESS_TOKEN" = "null" ] 
then 
   exit 1
fi

As @Tomaz correctly states, you cannot check both premisses at once using Bash syntax.

As @Kusanalanda also points out, the first test is irrelevant, and was just to make a point/explain if usage. Following the logic, if $ACCESS_TOKEN is tested again the string "null", then it is already implicit the string cannot be empty, so actually this can be rewritten as:

if [ "$ACCESS_TOKEN" = "null" ] 
then 
   exit 1
fi
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4
  • It seems as if the -n test is not needed. If the variable contains no value, it will not be equal to the string null (if that is supposed to be a string at all, sometimes people seems to thing it's a special value that denotes "no value"). Commented Dec 10, 2018 at 18:10
  • @Kusalananda Yeah, I just wrote this for the benefit of the understanding and syntax of the OP, besides being short in time. I also noticed the first condition is redundant. As for the actual string "null", some utilities indeed return "null" as a full string, in specific situations when they have nothing else to return or have not met a condition...jq is one of them, for instance, and in the past I found more doing that. Commented Dec 10, 2018 at 18:46
  • @Kusalananda taken from a script of mine here using jq too: if [ x"$S" == x"null" ] # end of array Commented Dec 10, 2018 at 18:50
  • @Tomaz is incorrect (though I could not find the referenced post). [ is not bash syntax and you cannot use && inside since [ is a command. bash syntax ([[) does support using && and || inside its test operators. Regardless, testing -n has no effect in this particular case Commented Jan 16, 2020 at 20:56
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Take a look at this:

[ -n "$ACCESS_TOKEN" -eq null ]

[ is the test operator and it can check either:

  • if a string value is not zero - when you use -n

  • compare two integers - when you use -eq

But not both at once! (Not in this form at least.) So you have to pick what you want to check in this [. And if you want to compare to null, then it would be a string comparison, which is done with the = operator.

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4
  • ... which is done with the = operator. Commented Dec 9, 2018 at 20:58
  • @MichaelHomer Are they not equivalent in Bash? Commented Dec 9, 2018 at 21:04
  • They are functionally equivalent in Bash, but documented as "= should be used with the test ([) command" (because = is in POSIX and == is not). It wasn't wrong. Commented Dec 9, 2018 at 21:11
  • @MichaelHomer The shell is not defined in the question, so it might be wrong. Commented Dec 9, 2018 at 21:15
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You could use shell's

Parameter Expansion . . . ${parameter:-word} Use Default Values. If parameter is unset or null, the expansion of word is substituted.

like

if [ "${ACCESS_TOKEN:-x}" = null ]; then echo Yes; else echo No; fi;

Be aware that it is the literal string "null" in the test, not the null "attribute" of the variable.

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