Why rename simply doesn't work?

Question

I need to rename multiple files, and some tutorials shows that the command rename is the best option instead of just use mv for each file.

But then I have these files:

 ReconhecimentoImagens2021-10-18--2020-2.mp4       ReconhecimentoImagens2021-11-01--2020-2.mp4   ReconhecimentoImagens2021-11-22--2020-2.mp4
 ReconhecimentoImagens2021-10-25--2020-2.mp4       ReconhecimentoImagens2021-11-08--2020-2.mp4   ReconhecimentoImagens2021-11-24--2020-2.mp4
'ReconhecimentoImagens2021-11-01--2020-2(2).mp4'   ReconhecimentoImagens2021-11-17--2020-2.mp4   ReconhecimentoImagens2021-11-29--2020-2.mp4

and just for a test I tried this command:

rename 's/2021/ /' *.mp4

and NOTHING happens, I get code 4 that according to the man page means 'nothing was renamed'.

I searched for multiple tutorials and nobody seems to be doing anything different than that so, what am I doing wrong here?

Answer 1

There's different versions of rename, and yours isn't the one with PERL regex support.

For most Linux distros and other unixoid systems, there's some package that contains the rename.pl or simply rename command that's built from perl.

In your use case, the "classical" util-linux rename fully suffices:

rename "2021" " "  *.mp4

would do.

Honestly, my shell does well enough that I don't have to remember all these fine things. I learned sed somewhat OK-ish once, I've learned my shell's for syntax once, and that's it:

for filename in *.mp4 ; do
  mv "${filename}" "$(echo "${filename}" | sed 's/regex/replacement/')"
done

is pretty easy to remember for me, at least, and should work in bash and zsh and other bourne-alike shells. Not an extra command I have to learn.

In fact, if you want things to be simple, you can use your own favourite shell's variable expansion to its fullest extent:

#!/usr/bin/env zsh
if [[ "${#}" -lt 2 ]] ; then 
  echo "Usage: ${0} [-r] PATTERN REPLACEMENT [FILE...]"
  echo "Uses normal Zsh globbing for pattern, unless -r is specified:"
  echo "In that case, use the regexp-replace loadable ZSH function"
  exit 1
fi

if [[ "${1}" = "-r" ]]; then
  autoload regexp-replace
  REGEX=1
  shift 1
else
  set -o extendedglob
  REGEX=0
fi

PATTERN="${1}"
REPLACEMENT="${2}"
shift 2

if [[ "${REGEX}" -eq 0 ]]; then
  for filename in ${argv} ; do
    mv "${filename}" "${filename/${1}/${2}}" || echo "Problem renaming ${filename}" >&2
  done
else
  for filename in ${argv} ; do
    original_filename="${filename}
    regexp_replace filename "${PATTERN}" "${REPLACEMENT}"
    mv "${original_filename} "${filename}" || echo "Problem renaming ${original_filename}" >&2
  done
fi