Implementing dry-run in bash scripts
How would one implement a dry-run option in a bash script?
I can think of either wrapping every single command in an if and echoing out the command instead of running it if the script is running with dry-run.
Another way would be to define a function and then passing each command call through that function.
Something like:
function _run () {
if [[ "$DRY_RUN" ]]; then
echo $@
else
$@
fi
}
`_run mv /tmp/file /tmp/file2`
`DRY_RUN=true _run mv /tmp/file /tmp/file2`
Is this just wrong and there is a much better way of doing it?
See BashFAQ/050: I'm trying to put a command in a variable, but the complex cases always fail! for a discussion of this subject.
Although now removed, the section How to add testing capability to a programs may still be useful.
I wanted to play with the answer from @Dennis Williamson's. Here's what I got:
Run () {
if [ "$TEST" ]; then
echo "$*"
return 0
fi
eval "$@"
}
The eval "$@"
is important here, and is better then simply doing $*
. $@
returns all parameters and $*
returns all parameters with no whitespace/quoting.
$ mkdir dir
$ touch dir/file1 dir/file2
$ FOO="dir/*"
$ TEST=true Run ls -l $FOO
ls -l dir/file1 dir/file2
$ Run ls -l $FOO
-rw-r--r-- 1 stefanl stefanl 0 Jun 2 21:06 dir/file1
-rw-r--r-- 1 stefanl stefanl 0 Jun 2 21:06 dir/file2