Incorrect exit code inside child script

Question

I have a parent script, that execute a child script in background:

#!/bin/bash
# parent.sh
childScript $param1 $param2&

Child script:

#!/bin/bash
# childScript.sh
param1=$1
param2=$2
someLinuxCommand $param1 $param2
out=$?
echo $out

If I execute childScript.sh with correct $param1 and $param2, $? will return 0. If $param1 and $param2 are incorrect, $? will return 1.

But no matter what $param1 and $param2 I send using parent.sh, $? always return 0. Why if I send incorrect $param1 and $param2 from parent.sh, $? in childScript.sh return 0?

Make sure returncode of someLinuxCommand is correct and then remove out=$? and echo $out. — Cyrus
– Cyrus, Commented Sep 22, 2017 at 8:08
If I execute childScript.sh with correct $param1 and $param2, $? will return 0. If $param1 and $param2 are incorrect, $? will return 1. — Serhii Didanov
– Serhii Didanov, Commented Sep 22, 2017 at 8:22
Shouldn't even run, there shouldn't be spaces between assignments. — 123
– 123, Commented Sep 22, 2017 at 8:28
I forgot about one moment, childScript executed in background (childScript $param1 $param2&) — Serhii Didanov
– Serhii Didanov, Commented Sep 22, 2017 at 8:44

Red Cricket · Accepted Answer · 2017-09-22 08:12:59Z

1

In your child script you are "returning" the result of echo which will always be 0. You should be using ...

exit $?

... instead. Or just leave that line out all together.

Here is an example that apes your scripts:

$ cat parent.sh
#!/bin/bash

p1=$1
p2='file'
./child.sh $p1 $p2

$ cat child.sh
#!/bin/sh

grep $1 $2
out=$?
echo $out

The child script will "grep" for the pattern in the "file". Here are the contents of the file "file".

$ cat file
c.sh
file
in.txt
p.sh
bill

If grep find the pattern in the file grep will succeed thus setting $? to 0. But if grep does not find the pattern in the file grep will fail this setting $? to 1.

Here we run parent with a pattern of "bob"

$ ./parent.sh bob
1

grep did not find bob in thus sets $? to 1. echo outputs 1 and then sets $? to 0.

$ echo $?
0

Let's fix the child.sh script to be:

$ cat child.sh
#!/bin/sh

grep $1 $2

and run parent.sh again:

$ ./parent.sh bob
$ echo $?
1

$ ./parent.sh bill
bill
$ echo $?
0

edited Sep 22, 2017 at 8:12

answered Sep 22, 2017 at 7:45

Red Cricket

10.6k24 gold badges96 silver badges193 bronze badges

Sign up to request clarification or add additional context in comments.

11 Comments

Red Cricket Over a year ago

Same answer though. Your child scripts exit code is that of a successful execution of echo. Don't do the echo $out. Exit code will be the exit code of echo which is not what you want.

Serhii Didanov Over a year ago

>>> If I execute childScript.sh with correct $param1 and $param2, $? will return 0. If $param1 and $param2 are incorrect, $? will return 1. Problem happens when I execute childScript.sh from parent script.

Red Cricket Over a year ago

Your scripts "return" an exit code which is set to errno of that last statement executed in the script.

Serhii Didanov Over a year ago

last statement executed in the childScript.sh (someLinuxCommand $param1 $param2) is incorrect, but $out == 0.

Red Cricket Over a year ago

No. That last statement executed in your child script is echo which succeeds thus setting $? to zero.

|

Collectives™ on Stack Overflow

Incorrect exit code inside child script

1 Answer 1

11 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

11 Comments

Your Answer

Sign up or log in

Post as a guest

Related