Two Linux shell scripting tips
Eventually you’ll find yourself writing some Linux shell script. That means soon you’ll find yourself debugging said script.
These couple things helped me a lot.
set -x
will display output that is very useful for debugging.
-x After expanding each simple command, for command, case command, select command, or arithmetic for command, display the expanded value of PS4, followed by the command and its expanded arguments or associated word list.
set -e
will stop the script immediately when some things fail. Makes your scripts safer.
-e Exit immediately if a pipeline (which may consist of a single simple command), a subshell command enclosed in parentheses, or one of the commands exe‐ cuted as part of a command list enclosed by braces (see SHELL GRAMMAR above) exits with a non-zero status. The shell does not exit if the command that fails is part of the command list immediately following a while or until keyword, part of the test following the if or elif reserved words, part of any command executed in a && or || list except the command following the final && or ||, any command in a pipeline but the last, or if the command’s return value is being inverted with !. A trap on ERR, if set, is executed before the shell exits. This option applies to the shell environment and each sub‐ shell environment separately (see COMMAND EXECUTION ENVIRONMENT above), and may cause subshells to exit before executing all the commands in the subshell.