A While Ago I Learned
Sometimes when you write a shell script, you need to temporarily save files somewhere, temporarily clone a Git repo, etc. This temporary data should be deleted once the script has completed.
Create a temporary directory
You can use the mktemp command to create a temporary file or
directory in the appropriate location depending on the operating system:
$> mktemp -d -t my-script
/var/folders/a0/8alqx_yap8dl30000ap/T/my-script.J3Fv0NWl
The -d option creates a directory instead of a file (the default).
The -t <prefix> option specifies a prefix so that your temporary directory is
named after your script and with a random suffix. It will be created in your
operating system’s standard location for temporary files (defined by the
$TMPDIR environment variable).
The directory is created with mode 0700 by default, meaning it should only be
accessible by you:
$> ls -la "$tmp_dir"
total 0
drwx------ 2 you your-group 64 Feb 6 17:19 .
drwx------@ 98 you your-group 3136 Feb 6 17:19 ..
You can store this temporary directory in a variable:
tmp_dir=$( mktemp -d -t my-script )
Define a cleanup function
This function will clean up the temporary directory, making sure it exists first
(in case the mktemp command failed):
clean_up() {
test -d "$tmp_dir" && rm -fr "$tmp_dir"
}
Automatically clean up on exit
You don’t want to call this cleanup function manually. Your script could fail before it is completed. It could receive a signal and exit.
However, you can use Bash’s built-in trap command to catch the EXIT
pseudo-signal. Your script will receive this signal when it closes, whether
successfully, unsuccessfully or due to an interrupt (e.g. the user hitting
Ctrl-C).
trap "clean_up $tmp_dir" EXIT
Do the magic
You can now write the rest of your script and put whatever you want in the temporary directory, safe in the knowledge that it will be automatically cleaned up at the end.
Here’s the complete version:
#!/usr/bin/env bash
clean_up() {
test -d "$tmp_dir" && rm -fr "$tmp_dir"
}
tmp_dir=$( mktemp -d -t my-script )
trap "clean_up $tmp_dir" EXIT
echo Do the magic...