[SOLVED] Detecting sys.exit() and ValueError from a python script in bash script

Issue

I created a bash script that manages multiple related python scripts based on specific conditions (i.e., run this script while file has < x number of lines, run a different script if..., etc.). I am using entry points to execute these python scripts within the bash script.

When validating the bash script I found some edge cases where all the conditions fail, resulting in a sys.exit(load_entry_point('Program', 'console_scripts', 'iter')()) and ValueError: Nothing was generated (designated within the python program to be raised if nothing happens).

After looking on SO, I tried something like this within some of my conditionals:

    if [ $? -ne 0 ];
    then
        echo "exit 1"
    fi
    echo "EXIT 0"

I continue to get EXIT 0, suggesting no errors are being detected. What I am not understanding here?

For clarity, my goal is to detect any errors thrown by the invoked python scripts to have the bash script respond accordingly.

---

Here is an idea of what the bash script is like:

Iter=1
while [ $nr_lines -lt 17 ]; do

    if [ $Iter -eq 5 ]; then

        echo ''
        echo 'Relax parameter. Iteration:' $Iter

        relax -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++

    else

        echo ''
        echo 'Iteration:' $Iter

        iter -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++
    fi
done

I have tried putting the conditional for error capturing here:

Iter=1
while [ $nr_lines -lt 17 ]; do

    if [ $Iter -eq 5 ]; then

        echo ''
        echo 'Relax parameter. Iteration:' $Iter

        relax -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++

    else

        echo ''
        echo 'Iteration:' $Iter

        iter -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++
    fi

    if [ $? -ne 0 ];
    then
        echo "exit 1"
    fi
    echo "EXIT 0"

done

and here:

Iter=1
while [ $nr_lines -lt 17 ]; do

    if [ $Iter -eq 5 ]; then

        echo ''
        echo 'Relax parameter. Iteration:' $Iter

        relax -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++

    else

        echo ''
        echo 'Iteration:' $Iter

        iter -i $Iter -o ./dir

        nr_lines=$(wc -l < ./dir/output$Iter.csv)
        
        let Iter++
    fi

done

if [ $? -ne 0 ];
then
    echo "exit 1"
fi
echo "EXIT 0"

and both return EXIT 0, suggesting no errors have occurred.

Solution

Change

        iter -i $Iter -o ./dir

to

        if ! iter -i $Iter -o ./dir
        then
            echo "iter failed"
            break
        fi

This directly tests the exit status of the python script run by iter. If it exits with a non-zero status, you print the message and break out of the while loop.

You can do similarly with relax.

Answered By - Barmar

Answer Checked By - Cary Denson (WPSolving Admin)