Better way to rename files based on multiple patterns

Question

a lot of files I download have crap/spam in their filenames, e.g.

[ www.crap.com ] file.name.ext

www.crap.com - file.name.ext

I've come up with two ways for dealing with them but they both seem pretty clunky:

with parameter expansion:

if [[ ${base_name} != ${base_name//\[+([^\]])\]} ]]
then
    mv -v "${dir_name}/${base_name}" "${dir_name}/${base_name//\[+([^\]])\]}" &&
        base_name="${base_name//\[+([^\]])\]}"
fi

if [[ ${base_name} != ${base_name//www.*.com - /} ]]
then
    mv -v "${dir_name}/${base_name}" "${dir_name}/${base_name//www.*.com - /}" &&
        base_name="${base_name//www.*.com - /}"
fi

# more of these type of statements; one for each type of frequently-encountered pattern

and then with echo/sed:

tmp=`echo "${base_name}" | sed -e 's/\[[^][]*\]//g' | sed -e 's/\s-\s//g'`
mv "${base_name}" "{tmp}"

I feel like the parameter expansion is the worse of the two but I like it because I'm able to keep the same variable assigned to the file for further processing after the rename (the above code is used in a script that's called for each file after the file download is complete).

So anyway I was hoping there's a better/cleaner way to do the above that someone more knowledgeable than myself could show me, preferably in a way that would allow me to easily reassign the old/original variable to the new/renamed file.

Thanks

Answer 1

Two answer: using perl rename or using pure bash

As there are some people who dislike perl, I wrote my bash only version

Renaming files by using the rename command.

Introduction

Yes, this is a typical job for rename command which was precisely designed for:

man rename | sed -ne '/example/,/^[^ ]/p'
   For example, to rename all files matching "*.bak" to strip the
   extension, you might say

           rename 's/\.bak$//' *.bak

   To translate uppercase names to lower, you'd use

           rename 'y/A-Z/a-z/' *

More oriented samples

Simply drop all spaces and square brackets:

rename 's/[ \[\]]*//g;' *.ext

Rename all .jpg by numbering from 1:

rename 's/^.*$/sprintf "IMG_%05d.JPG",++$./e' *.jpg

Demo:

touch {a..e}.jpg
ls -ltr
total 0
-rw-r--r-- 1 user user 0 sep  6 16:35 e.jpg
-rw-r--r-- 1 user user 0 sep  6 16:35 d.jpg
-rw-r--r-- 1 user user 0 sep  6 16:35 c.jpg
-rw-r--r-- 1 user user 0 sep  6 16:35 b.jpg
-rw-r--r-- 1 user user 0 sep  6 16:35 a.jpg
rename 's/^.*$/sprintf "IMG_%05d.JPG",++$./e' *.jpg
ls -ltr
total 0
-rw-r--r-- 1 user user 0 sep  6 16:35 IMG_00005.JPG
-rw-r--r-- 1 user user 0 sep  6 16:35 IMG_00004.JPG
-rw-r--r-- 1 user user 0 sep  6 16:35 IMG_00003.JPG
-rw-r--r-- 1 user user 0 sep  6 16:35 IMG_00002.JPG
-rw-r--r-- 1 user user 0 sep  6 16:35 IMG_00001.JPG

Full syntax for matching SO question, in safe way

There is a strong and safe way using rename utility:

As this is perl common tool, we have to use perl syntax:

rename 'my $o=$_;
        s/[ \[\]]+/-/g;
        s/-+/-/g;
        s/^-//g;
        s/-\(\..*\|\)$/$1/g;
        s/(.*[^\d])(|-(\d+))(\.[a-z0-9]{2,6})$/
                my $i=$3;
                $i=0 unless $i;
                sprintf("%s-%d%s", $1, $i+1, $4)
            /eg while
               $o ne $_  &&
               -f $_;
    ' *

Testing rule:

touch '[ www.crap.com ] file.name.ext' 'www.crap.com - file.name.ext'
ls -1
[ www.crap.com ] file.name.ext
www.crap.com - file.name.ext
rename 'my $o=$_; ...
    ...
    ...' *
ls -1
www.crap.com-file.name-1.ext
www.crap.com-file.name.ext

touch '[ www.crap.com ] file.name.ext' 'www.crap.com - file.name.ext'
ls -1
www.crap.com-file.name-1.ext
[ www.crap.com ] file.name.ext
www.crap.com - file.name.ext
www.crap.com-file.name.ext
rename 'my $o=$_; ...
    ...
    ...' *
ls -1
www.crap.com-file.name-1.ext
www.crap.com-file.name-2.ext
www.crap.com-file.name-3.ext
www.crap.com-file.name.ext

... and so on...

... and it's safe while you don't use -f flag to rename command: file won't be overwrited and you will get an error message if something goes wrong.

Renaming files by using bash and so called bashisms:

I prefer doing this by using dedicated utility, but this could even be done by using pure bash (aka without any fork)

There is no use of any other binary than bash (no sed, awk, tr or other):

#!/bin/bash

for file;do
    newname=${file//[ \]\[]/.}
    while [ "$newname" != "${newname#.}" ] ;do
        newname=${newname#.}
      done
    while [ "$newname" != "${newname//[.-][.-]/.}" ] ;do
        newname=${newname//[.-][.-]/-};done
    if [ "$file" != "$newname" ] ;then
        if [ -f $newname ] ;then
            ext=${newname##*.}
            basename=${newname%.$ext}
            partname=${basename%%-[0-9]}
            count=${basename#${partname}-}
            [ "$partname" = "$count" ] && count=0
            while printf -v newname "%s-%d.%s" $partname $[++count] $ext &&
                  [ -f "$newname" ] ;do
              :;done
          fi
        mv  "$file" $newname
      fi
  done

To be run with files as argument, for sample:

/path/to/my/script.sh \[*

• Replacing spaces and square bracket by dot
• Replacing sequences of .-, -., -- or .. by only one -.
• Test if filename don't differ, there is nothing to do.
• Test if a file exist with newname...
• split filename, counter and extension, for making indexed newname
• loop if a file exist with newname
• Finaly rename the file.

Answer 2

Take advantage of the following classical pattern:

 job_select /path/to/directory| job_strategy | job_process

where job_select is responsible for selecting the objects of your job, job_strategy prepares a processing plan for these objects and job_process eventually executes the plan.

This assumes that filenames do not contain a vertical bar | nor a newline character.

The job_select function

 # job_select PATH
 #  Produce the list of files to process
 job_select()
 {
   find "$1" -name 'www.*.com - *' -o -name '[*] - *'
 }

The find command can examine all properties of the file maintained by the file system, like creation time, access time, modification time. It is also possible to control how the filesystem is explored by telling find not to descend into mounted filesystems, how much recursions levels are allowed. It is common to append pipes to the find command to perform more complicated selections based on the filename.

Avoid the common pitfall of including the contents of hidden directories in the output of the job_select function. For instance, the directories CVS, .svn, .svk and .git are used by the corresponding source control management tools and it is almost always wrong to include their contents in the output of the job_select function. By inadvertently batch processing these files, one can easily make the affected working copy unusable.

The job_strategy function

# job_strategy
#  Prepare a plan for renaming files
job_strategy()
{
  sed -e '
    h
    s@/www\..*\.com - *@/@
    s@/\[^]]* - *@/@
    x
    G
    s/\n/|/
  '
}

This commands reads the output of job_select and makes a plan for our renaming job. The plan is represented by text lines having two fields separated by the character |, the first field being the old name of the file and the second being the new computed file of the file, it looks like

[ www.crap.com ] file.name.1.ext|file.name.1.ext
www.crap.com - file.name.2.ext|file.name.2.ext

The particular program used to produce the plan is essentially irrelevant, but it is common to use sed as in the example; awk or perl for this. Let us walk through the sed-script used here:

h       Replace the contents of the hold space with the contents of the pattern space.
…       Edit the contents of the pattern space.
x       Swap the contents of the pattern and hold spaces.
G       Append a newline character followed by the contents of the hold space to the pattern space.
s/\n/|/ Replace the newline character in the pattern space by a vertical bar.

It can be easier to use several filters to prepare the plan. Another common case is the use of the stat command to add creation times to file names.

The job_process function

# job_process
#  Rename files according to a plan
job_process()
{
   local oldname
   local newname
   while IFS='|' read oldname newname; do
     mv "$oldname" "$newname"
   done
}

The input field separator IFS is adjusted to let the function read the output of job_strategy. Declaring oldname and newname as local is useful in large programs but can be omitted in very simple scripts. The job_process function can be adjusted to avoid overwriting existing files and report the problematic items.

About data structures in shell programs Note the use of pipes to transfer data from one stage to the other: apprentices often rely on variables to represent such information but it turns out to be a clumsy choice. Instead, it is preferable to represent data as tabular files or as tabular data streams moving from one process to the other, in this form, data can be easily processed by powerful tools like sed, awk, join, paste and sort — only to cite the most common ones.