如何从Shell脚本返回特定变量的值？

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"

Answer 1

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.

Answer 2

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

Answer 3

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