CODEWITHSUNDEEP
linuxfunctionshellash
MOHAMED
MOHAMED

Reputation: 43528

Check if a function exists before executing it in shell

I want to check if a function exist or not before executing it in the shell script.

Does script shell support that? and how to do it?

Upvotes: 5

Views: 5425

Answers (3)

Jens
Jens

Reputation: 72667

POSIX does not specify any arguments for the type built-in and leaves its output unspecified. Your best bet, apart from a shell-specific solution, is probably

if type foo | grep -i function > /dev/null; then
   # foo is a function
fi

Upvotes: 1

chepner
chepner

Reputation: 531430

You can always just try executing the function. If it doesn't exist, the exit status of the command will be 127:

$ myfunction arg1 arg2 || {
>  if [ $? -ne 127 ]; then
>    echo Error with my function
>  else
>    echo myfunction undefined
>  fi; }

Of course, the function may have the same name as another binary, and you may not want to run that program if it is not shadowed by the function.

Upvotes: 0

fedorqui
fedorqui

Reputation: 289835

As read in this comment, this should make it:

type -t function_name

this returns function if it is a function.

Test

$ type -t f_test
$ 
$ f_test () { echo "hello"; }
$ type -t f_test
function

Note that type provides good informations:

$ type -t ls
alias
$ type -t echo
builtin

Upvotes: 7

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