How can I create a temp file with a specific extension in bash?

Question

I'm writing a shell script, and I need to create a temporary file with a certain extension.

I've tried

tempname=`basename $0` TMPPS=`mktemp /tmp/${tempname}.XXXXXX.ps` || exit 1 

and

tempname=`basename $0` TMPPS=`mktemp -t ${tempname}` || exit 1 

neither work, as the first creates a file name with a literal "XXXXXX" and the second doesn't give an option for an extension.

I need the extension so that preview won't refuse to open the file.

Edit: I ended up going with a combination of pid and mktemp in what I hope is secure:

tempname=`basename $0` TMPTMP=`mktemp -t ${tempname}` || exit 1 TMPPS="$TMPTMP.$$.ps"  mv $TMPTMP $TMPPS || exit 1 

It is vulnerable to a denial of service attack, but I don't think anything more severe.

Answer 1

Recent versions of mktemp offer --suffix:

   --suffix=SUFF           append SUFF to TEMPLATE.  SUFF must not contain slash.  This option is implied if TEMPLATE does not end in X.  $ mktemp /tmp/banana.XXXXXXXXXXXXXXXXXXXXXXX.mp3 /tmp/banana.gZHvMJfDHc2CTilINNuq2P0.mp3 

I believe this requires coreutils >= 8 or so.

If you create a temp file (older mktemp version) without suffix and you're renaming that to append one, the least thing you could probably do is check if the file already exists. It doesn't protect you from race conditions, but it does protect you if there's already such a file which has been there for a while.

Answer 2

How about this one:

echo $(mktemp $TMPDIR/$(uuidgen).txt)