why return statement in function will cause the bash script end

Question

when I run the follow bash script, it will never print "bye!". It seems that return statement in dummy function will cause the bash script end, leave the left script not excute.

#!/bin/bash -ex

dummy () {
    if [ $1 -eq 0 ] ; then 
        return 0
    else
        return 55
    fi  
}

dummy 0
echo "when input 0, dummy will return $?"

dummy 50
echo "when input 50, dummy will return $?"

echo "bye!"

output:

+ dummy 0
+ '[' 0 -eq 0 ']'
+ return 0
+ echo 'when input 0, dummy will return 0'
when input 0, dummy will return 0
+ dummy 50
+ '[' 50 -eq 0 ']'
+ return 55

holygeek · Accepted Answer · 2011-08-19 08:46:35Z

8

Your she-bang line: #!/bin/bash -ex

That -e option tells bash to exit immediately after a command returns a non-zero value.

In this case it's the [ $1 -eq 0 ] when $1 is 55 so your script exits immediately.

Try run you script like this:

$ bash yourscript.sh

vs.:

$ bash -e yourscript.sh

answered Aug 19, 2011 at 8:46

holygeek

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5 Comments

Bruno Flávio Over a year ago

I couldn't find the -e option in gnu bash manual. You don't happen to have a link to a reference where I can read/learn about it?

holygeek Over a year ago

@Qsp It's in the bash manual, "buried" deep among the options. Run this in your bash shell to see the relevant paragraphs: man bash|col -b|grep -A3 'OPTIONS'; man bash|col -b|grep -A 2 -- '-e *Exit'

Leon Over a year ago

@holygeek what's means of "--" in command "man bash|col -b|grep -A 2 -- '-e *Exit'"

holygeek Over a year ago

@Leon -- tells grep that everything that comes after it are not to be treated as command line switches anymore. They are arguments. Without it grep would treat that '-e *Exit' as another switch. The use of -- is supported by programs that use the getopt library for processing command line switches and arguments.

Rebs Over a year ago

I assume the -ex is the same as set -e; set-x which is documented here: gnu.org/software/bash/manual/…

Bruno Flávio · Accepted Answer · 2011-08-19 08:45:08Z

0

change

#!/bin/bash -ex

to:

#!/bin/bash

and it will work.

Actually you can do it with #!/bin/bash -x also.

You meant to accomplish something else with the -e option?

answered Aug 19, 2011 at 8:45

Bruno Flávio

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Comments

pyvi · Accepted Answer · 2011-08-19 10:51:53Z

-2

Use single quotes around 'bye!'. With double quotes the "!" causes a problem.

edited Aug 19, 2011 at 10:51

pyvi

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answered Aug 19, 2011 at 8:43

Yends

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1 Comment

tripleee Over a year ago

At the prompt, exclamations are problematic even in single quotes, but in a script file, they're not. At the prompt, the exclamation mark is used by the csh-like history substitution mechanism (die, csh! die, history substitution mechanism from csh!)

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