How to return a string value from a Bash function

Question

I'd like to return a string from a Bash function.

I'll write the example in java to show what I'd like to do:

public String getSomeString() {   return "tadaa"; }  String variable = getSomeString(); 

The example below works in bash, but is there a better way to do this?

function getSomeString {    echo "tadaa" }  VARIABLE=$(getSomeString) 

Answer 1

You could have the function take a variable as the first arg and modify the variable with the string you want to return.

#!/bin/bash set -x function pass_back_a_string() {     eval "$1='foo bar rab oof'" }  return_var='' pass_back_a_string return_var echo $return_var 

Prints "foo bar rab oof".

Edit: added quoting in the appropriate place to allow whitespace in string to address @Luca Borrione's comment.

Edit: As a demonstration, see the following program. This is a general-purpose solution: it even allows you to receive a string into a local variable.

#!/bin/bash set -x function pass_back_a_string() {     eval "$1='foo bar rab oof'" }  return_var='' pass_back_a_string return_var echo $return_var  function call_a_string_func() {      local lvar=''      pass_back_a_string lvar      echo "lvar='$lvar' locally" }  call_a_string_func echo "lvar='$lvar' globally" 

This prints:

+ return_var= + pass_back_a_string return_var + eval 'return_var='\''foo bar rab oof'\''' ++ return_var='foo bar rab oof' + echo foo bar rab oof foo bar rab oof + call_a_string_func + local lvar= + pass_back_a_string lvar + eval 'lvar='\''foo bar rab oof'\''' ++ lvar='foo bar rab oof' + echo 'lvar='\''foo bar rab oof'\'' locally' lvar='foo bar rab oof' locally + echo 'lvar='\'''\'' globally' lvar='' globally 

Edit: demonstrating that the original variable's value is available in the function, as was incorrectly criticized by @Xichen Li in a comment.

#!/bin/bash set -x function pass_back_a_string() {     eval "echo in pass_back_a_string, original $1 is \$$1"     eval "$1='foo bar rab oof'" }  return_var='original return_var' pass_back_a_string return_var echo $return_var  function call_a_string_func() {      local lvar='original lvar'      pass_back_a_string lvar      echo "lvar='$lvar' locally" }  call_a_string_func echo "lvar='$lvar' globally" 

This gives output:

+ return_var='original return_var' + pass_back_a_string return_var + eval 'echo in pass_back_a_string, original return_var is $return_var' ++ echo in pass_back_a_string, original return_var is original return_var in pass_back_a_string, original return_var is original return_var + eval 'return_var='\''foo bar rab oof'\''' ++ return_var='foo bar rab oof' + echo foo bar rab oof foo bar rab oof + call_a_string_func + local 'lvar=original lvar' + pass_back_a_string lvar + eval 'echo in pass_back_a_string, original lvar is $lvar' ++ echo in pass_back_a_string, original lvar is original lvar in pass_back_a_string, original lvar is original lvar + eval 'lvar='\''foo bar rab oof'\''' ++ lvar='foo bar rab oof' + echo 'lvar='\''foo bar rab oof'\'' locally' lvar='foo bar rab oof' locally + echo 'lvar='\'''\'' globally' lvar='' globally 

Answer 2

There is no better way I know of. Bash knows only status codes (integers) and strings written to the stdout.