Question

Is there a better way to save a command line before it it executed?

A number of my /bin/bash scripts construct a very long command line. I generally save the command line to a text file for easier debugging and (sometimes) execution.

My code is littered with this idiom:

echo >saved.txt cd $NEW_PLACE '&&' command.py --flag $FOO $LOTS $OF $OTHER $VARIABLES
                cd $NEW_PLACE && command.py --flag $FOO $LOTS $OF $OTHER $VARIABLES

Obviously updating code in two places is error-prone. Less obvious is that Certain parts need to be quoted in the first line but not the next. Thus, I can not do the update by simple copy-and-paste. If the command includes quotes, it gets even more complicated.

There has got to be a better way! Suggestions?

Answer 1

How about creating a helper function which logs and then executes the command? "$@" will expand to whatever command you pass in.

log() {
    echo "$@" >> /tmp/cmd.log
    "$@"
}

Use it by simply prepending log to any existing command. It won’t handle && or || though, so you’ll have to log those commands separately.

log cd $NEW_PLACE && log command.py --flag $FOO $LOTS $OF $OTHER $VARIABLES