I have two Bash scripts. The parent scripts calls the subscript to perform some actions and return a value. How can I return a value from the subscript to the parent script? Adding a return in the subscript and catching the value in the parent did not work.
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1Take a look at this answer from yesterday: stackoverflow.com/a/16325765/1983854 - it may help a lotfedorqui– fedorqui2013-05-02 12:29:43 +00:00Commented May 2, 2013 at 12:29
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3 Answers
I am assuming these scripts are running in two different processes, i.e. you are not "sourcing" one of them.
It depends on what you want to return. If you wish only to return an exit code between 0 and 255 then:
# Child (for example: 'child_script')
exit 42
# Parent
child_script
retn_code=$?
If you wish to return a text string, then you will have to do that through stdout (or a file). There are several ways of capturing that, the simplest is:
# Child (for example: 'child_script')
echo "some text value"
# Parent
retn_value=$(child_script)
4 Comments
Akhil F
Does the echo method return everything echo'd by the child script or just the last line?
cdarke
@AakilFernandes: in this case,
echo writes the line given to it: "some text value" in the example. However, the parent is capturing all the standard output from the child, whether it came from an echo or not. That could be multiple lines separated by newlines $'\n'
Saltuk Kezer
@cdarke What if i just want the last line to be captured by the parent?
Here is another way to return a text value from a child script using a temporary file. Create a tmp file in the parent_script and pass it to the child_script. I prefer this way over parsing output from the script
Parent
#!/bin/bash
# parent_script
text_from_child_script=`/bin/mktemp`
child_script -l $text_from_child_script
value_from_child=`cat $text_from_child_script`
echo "Child value returned \"$value_from_child\""
rm -f $text_from_child_script
exit 0
Child
#!/bin/bash
# child_script
# process -l parm for tmp file
while getopts "l:" OPT
do
case $OPT in
l) answer_file="${OPTARG}"
;;
esac
done
read -p "What is your name? " name
echo $name > $answer_file
exit 0
Comments
return a value from the subscript and check the variable $? which contain the return value
3 Comments
chepner
"Return" is ambiguous here, as the
return statement can only be used to return from a function, not a script. To be precise, you need to use the exit statement to return from the script.cdarke
@chepner: actually
return can also be used from a "sourced" file ( . or source command), but is that then a script?chepner
Ah, tricky. I guess the right answer then is "use
return or exit as appropriate".