Bash mktemp

edit ✏️

There is GNU coreutils command called mktemp that is super handy in shell scripts to make temporary landing spots for files so that they never clash with another instance, and will automatically get cleaned up when you restart, or whenever /tmp gets wiped. I'm not sure when that is, but I don't expect it to be long.

Making temp directories

Here are some examples of making temp directories in different places, my favorite is mktemp -dt mytemp-XXXXXX .

# makes a temporary directory in /tmp/ with the defaul template tmp.XXXXXXXXXX
mktemp

# makes a temporary directory in your current directory
mktemp --directory mytemp-XXXXXX
# shorter version
mktemp -d mytemp-XXXXXX

# same thing, but makes a file
mktemp mytemp-XXXXXX

# makes a temporary directory in your /tmp/ directory (or what ever you have configured as your TMPDIR)
mktemp --directory --tmpdir mytemp-XXXXXX
# shorter version
mktemp -dt mytemp-XXXXXX

# same thing, but makes a file
mktemp --tmpdir mytemp-XXXXXX
# shorter version
mktemp -t mytemp-XXXXXX

Use Case

Here is a sample script that shows how to capture the tempdir as a variable and reuse it. Here is an example of curling my bootstrap file into a temp directory and running it from that directory.

local tmp=`mktemp -dt bootstrap-XXXXXX`
pushd $tmp
curl https://raw.githubusercontent.com/WaylonWalker/devtainer/main/bootstrap > bootstrap
bash bootstrap
popd

Templates

You must have at least 3 trailing X's that mktemp will replace with random characters. I played with it for a bit, it kinda allows for some trailing characters, and will not fill groups of X's earlier in your template, only the last consecutive string.

My randomm samples I played with.

waylonwalker.com on  main [!?]  v3.9.7 (waylonwalker.com) took 2m24s
❯ mktemp myXtemp-XaXbXXXX -dt
/tmp/myXtemp-XaXbx9hn

waylonwalker.com on  main [!?]  v3.9.7 (waylonwalker.com)
❯ mktemp myXtemp-XaXbXXXXs -dt
/tmp/myXtemp-XaXb2tpGs

waylonwalker.com on  main [!?]  v3.9.7 (waylonwalker.com)
❯ mktemp myXtemp-XaXbXXcXXs -dt
mktemp: too few X's in template ‘myXtemp-XaXbXXcXXs’

waylonwalker.com on  main [!?]  v3.9.7 (waylonwalker.com)
❯ mktemp myXtemp-XaXbXXcXXs -dt

waylonwalker.com on  main [!?]  v3.9.7 (waylonwalker.com)
❯ mktemp myXtemp-XaXbXXXXt -dt
/tmp/myXtemp-XaXbe8PWt

waylonwalker.com on  main [!?]  v3.9.7 (waylonwalker.com)
❯ mktemp myXtemp-XXX-you-XXX -dt
/tmp/myXtemp-XXX-you-48l

waylonwalker.com on  main [!?]  v3.9.7 (waylonwalker.com)
❯ mktemp myXtemp-XXX-you-XX -dt
mktemp: too few X's in template ‘myXtemp-XXX-you-XX’

RTFM

The man page has good stuff on all the flags that you might need.

man mktemp