Detecting whether a process completed successfully

[Simon]

Here’s a neat little construction that checks the exit status of a process. In this example, I’m using HLEd to find MLFs that have problems:

HLEd -I $MLF /dev/null 
if [ $? -ne 0 ]; then
     echo "Error from HLEd - there is a problem with " ${MLF}

I’m asking HLEd to load the MLF, and to do nothing (it needs a “editing command” file, for which I am providing the special empty system file /dev/null).

$? contains the exit status of the most recent process. A value of 0 indicates success.

[Harriet C]

Could you please give me some guidance on how to write something into my script which runs all the scripts consecutively so that if an error occurs it catches which username the error is for and prints this into a text file, so that these users can be excluded? Thank you

[Simon]

#!/usr/local/bin/bash

echo "This is the child script"

# let's run an HTK command, but with a deliberate mistake to cause an error
HInit -T 1 this_file_does_not_exist

# at this point, the special shell variable $? contains the exit status of HInit
# for readability, let's put that status into a variable with a nicer name
STATUS=$?

# test whether the return status is 0 (indicates success)
if [ ${STATUS} = 0 ]
then
	echo "HInit ran without error"
else
	echo "Something went wrong in HInit, which exited with code "${STATUS}
	# a good idea is to exit this script with the same error code
	# (or some other non-zero value, if you prefer)
	# so that anything calling this script can also detect the error
	exit ${STATUS}
fi

[Simon]

Put the above code in a file called child_script and try calling it from another script, to demonstrate that child_script correctly returns an exit status

#!/usr/local/bin/bash
echo "This is the parent script"

# let's call the child script
./child_script

# at this point, the special shell variable $? contains the exit status of child_script
# for readability, let's put that status into a variable with a nicer name
STATUS=$?

if [ ${STATUS} = 0 ]
then
	echo "The child script ran OK"
else
	echo "In parent script: child script returned error code "${STATUS}

	# exiting with any non-zero value indicates an error
	exit 1
fi

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