Shell – Setting env variable through script on current session

Regarding testing whether a "variable is 0", one can use:

if [ "$MYVAR" -eq 0 ] ; then exit ; fi

Or, if you prefer:

if [[ $MYVAR -eq 0 ]] ; then exit ; fi

The expression [[ -n "$MYVAR" ]] tests for a non-empty string value of MYVAR. The string "0" is non-empty: it has one character, the same as the string "1".

exit will cause the script to exit. return, by contrast, is used in functions or sourced scripts when you want to quit the function or sourced script but continue with execution of the calling script. Running exit in a function would cause both the function and its calling script to exit.

$SOMEPATH isn't defined within cron, so your crontab line that tries to source /$SOMEPATH/some.env will fail. (Unless //some.env exists, that is.)

For debugging cron related issues, be aware that it writes stderr messages - including its own - to the local user's mailbox. If you don't have a mail client installed (mail or mailx) you could use something like this to read these messages:

less /var/mail/$USER

Or if you want to be really generic

"${PAGER:-less}" "${MAIL:-/var/mail/${USER:-${LOGIN:-$(whoami)}}}"