How to remove part of file names between periods?

I would like to rename many files in this format

abc.123.fits
abcd.1234.fits
efg.12.fits

to this format

abc.fits
abcd.fits
efg.fits

I tried the rename function, but since the part I'm trying to replace is not the same in all files, it did not work. I am using Linux.

Solution

for f in *; do mv "$f" "${f%%.*}.${f##*.}"; done`

${f%%.*} removes everything after the first period, including the period. ${f##*.} removes everything before the last period, including the period (i.e. it gets the file extension). Concatenating these two, with a period between them, gives you the desired result.

You can change the * to a more restrictive pattern such as *.fits if you don't want to rename all files in the current directory. The quotes around the parameters to mv are necessary if any filenames contain whitespace.

Many other variable substitution expressions are available in bash; see a reference such as TLDP's Bash Parameter Substitution for more information.