mjhjmtu

I'm trying to rename a few images:

IMG_1.JPG
IMG_2.JPG
IMG_3.JPG

I want to replace IMG with img and .JPG with .jpg - I know how to do the second part:

$ rename 's/.JPG$/.jpg/' *.JPG

My problem is that I can't seem to mv IMG_.JPG to img_.jpg - I know you can pass multiple patterns to rename, but I can't seem to use the existing filename with an amended lowercase value.

How do I go about this?

Maybe you need to be using the perl rename command. On my CentOS box, it's called 'prename'.

$ ls
IMG_1.JPG IMG_2.JPG IMG_3.JPG
$ prename 's/^IMG/img/;s/.JPG$/.jpg/' *JPG
$ ls
img_1.jpg img_2.jpg img_3.jpg
$

$ prename -h
Usage: prename [OPTION]... PERLEXPR FILE...
Rename FILE(s) using PERLEXPR on each filename.

 -b, --backup make backup before removal
 -B, --prefix=SUFFIX set backup filename prefix
 -f, --force remove existing destinations, never prompt
 -i, --interactive prompt before overwrite
 -l, --link-only link file instead of reame
 -n, --just-print, --dry-run don't rename, implies --verbose
 -v, --verbose explain what is being done
 -V, --version-control=METHOD override the usual version control
 -Y, --basename-prefix=PREFIX set backup filename basename prefix
 -z, -S, --suffix=SUFFIX set backup filename suffix
 --help display this help and exit
 --version output version information and exit

The backup suffix is ~, unless set with SIMPLE_BACKUP_SUFFIX. The
version control may be set with VERSION_CONTROL, values are:

 numbered, t make numbered backups
 existing, nil numbered if numbered backups exist, simple otherwise
 simple, never always make simple backups

Report bugs to pederst@cpan.org
$

If you want to use the dumb rename command from util-linux (sometimes called rename.ul), perhaps needs doing in two steps, e.g.

$ ls
IMG_1.JPG IMG_2.JPG IMG_3.JPG
$ rename IMG img *JPG
$ rename JPG jpg *JPG
$ ls
img_1.jpg img_2.jpg img_3.jpg
$

To answer you question in the generic,

rename multiple files with 2 conditions/replacements in one line?

you would typically use capture groups, referring to them in the replacement expression using their corresponding backreferences. For example

$ rename -n 's/^(.*)_(.*).JPG$/L$1_$2.jpg/' *.JPG
rename(IMG_2.JPG, img_2.jpg)
rename(IMG_3.JPG, img_3.jpg)

However, in this particular case, it would be simpler to just apply the lowercase modifier L to the whole name:

$ rename -n 's/.*/L$&/' *.JPG
rename(IMG_2.JPG, img_2.jpg)
rename(IMG_3.JPG, img_3.jpg)

Another alternative, using mmv

$ mmv -n '*.JPG' '#l1.jpg'
IMG_2.JPG -> img_2.jpg
IMG_3.JPG -> img_3.jpg

(remove the -n to actually perform the rename).

Using mv:

sh compatible:

for file in *.JPG; do mv "$file" "$(echo "$file" | tr '[:upper:]' '[:lower:]')"; done

bash (Thanks steeldriver):

for file in *.JPG; do mv "$file" "$file,,"; done

This will loop through all .JPG files in the current directory and rename them to the same name with all uppercase characters converted to lowercase characters.

The simplest way and based on the man page that does not cover a regular expression:

rename 'IMG' 'img' * ; rename 'JPG' 'jpg' *