Re: Revisiting Error handling (errexit)

[Kerin Millar]

On Fri, 8 Jul 2022 13:22:46 +0300
Oğuz <oguzismailuysal@gmail.com> wrote:

> 8 Temmuz 2022 Cuma tarihinde Yair Lenga <yair.lenga@gmail.com> yazdı:
> >
> > Practical Example - real life. A job has to copy 3 critical data files. It
> > then sends notification via email (non-critical).
> >
> > #! /bin/bash
> > set -o errfail
> > function copy-files {
> >      # ALL files are critical, script will not cont
> >      cp /new/file1 /production/path/
> >      cp /new/file2 /production/path/
> >      # Use the files for something - e.g., count the lines.
> >      important-job /production/path/file1 /production/path/file2
> >
> >      ls -l /production/path | mail -s "all-good" notify@company.com ||
> > true    # Not critical
> > }
> >
> > if copy-files ; then
> >      more-critical-jobs
> >       echo "ALL GOOD"
> > else
> >       mail -s "PROBLEM" norify@company.com < /dev/null
> > fi
> >
> > What is the difference ? consider the case where /new/file1 does not
> > exists, which is critical error.
> > * Without errfail, an error message will be sent to script stderr, but the
> > script will continue to copy the 2nd file, and to perform the
> > important-job, even though the data is not ready.
> 
> 
> How is this any better than doing `cp ... && cp ... && important-job ...'?

Just to elaborate on the premise of the question, rather than address the 
question itself, the sample could have been written as:

#!/bin/bash

copy_files() {
        cp /new/file1 /production/path/ &&
        cp /new/file2 /production/path/ &&
        important-job /production/path/file1 /production/path/file2
}

if copy_files; then
        ls -l /production/path | mail -s "all-good" notify@company.com
        echo "ALL GOOD"
else
        mail -s "PROBLEM" notify@company.com < /dev/null
        false # not in the original but one probably wanted either this or exit 
1
fi

Alternatively, if it is considered necessary to issue ls from within the 
function:

copy_files() {
        cp /new/file1 /production/path/ &&
        cp /new/file2 /production/path/ &&
        important-job /production/path/file1 /production/path/file2 || return
        ls -l /production/path | mail -s "all-good" notify@company.com
        true
}

Ultimately, which approach is easier to reason with? Consider it as an open 
question.

-- 
Kerin Millar