How to return a specific variable's value from a shell script?

Question

I've got two sh files, which are "main.sh" and "sub.sh" i want to return a variable's value inside "sub.sh" and use it inside main.sh .There is so many "echo" command so i can't just return the value from sub.sh file. I need only one variable's value. How can that be possible?

main.sh

echo "start"

//how to get a variable from the sh below?
//dene=$(/root/sub.sh)

echo "finish"

sub.sh

echo "sub function"
 a="get me out of there"  // i want to return that variable from script
echo "12345"
echo  "kdsjfkjs"

You know, your syntax is not Bash. For example, those aren't bash comments. — John Zwinck
– John Zwinck, Commented Feb 11, 2014 at 11:13
i edited the "variable a" line. changed to just "a". I need a command like "sh main.sh | grep "delimiter" " — AloneInTheDark
– AloneInTheDark, Commented Feb 11, 2014 at 11:16
just print the variable a only it get the value in main.sh process. — Chandru
– Chandru, Commented Feb 11, 2014 at 11:17

John Zwinck · Accepted Answer · 2014-02-11 11:18:01Z

3

To "send" the variable, do this:

echo MAGIC: $a

To "receive" it:

dene=$(./sub.sh | sed -n 's/^MAGIC: //p')

What this does is to discard all lines that don't start with MAGIC: and print the part after that token when a match is found. You can substitute your own special word instead of MAGIC.

Edit: or you could do it by "source"ing the sub-script. That is:

source sub.sh
dene=$a

What that does is to run sub.sh in the context of main.sh, as if the text were just copy-pasted right in. Then you can access the variables and so on.

answered Feb 11, 2014 at 11:18

John Zwinck

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Fleshgrinder · Accepted Answer · 2014-02-11 11:20:39Z

1

main.sh

#!/bin/sh

echo "start"

# Optionally > /dev/null to suppress output of script
source /root/sub.sh

# Check if variable a is defined and contains sth. and print it if it does
if [ -n "${a}" ]; then
    # Do whatever you want with a at this point
    echo $a
fi

echo "finish"

sub.sh

#!/bin/sh

echo "sub function"
a="get me out of there"
echo "12345"
echo -e "kdsjfkjs"
exit 42

answered Feb 11, 2014 at 11:20

Fleshgrinder

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rjhdby · Accepted Answer · 2014-02-11 19:19:03Z

1

You can export variable to shell session in sub.sh and catch it later in main.sh.

sub.sh
#!/usr/bin/sh
export VARIABLE="BLABLABLA"


main.sh
#!/bin/sh
. ./sub.sh
echo $VARIABLE

edited Feb 11, 2014 at 19:19

answered Feb 11, 2014 at 18:32

rjhdby

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