perl-rename

TLDR

Rename files using a Perl Common Regular Expression (substitute 'foo' with 'bar' wherever found)

$ rename ['s/foo/bar/'] [*]

Dry-run - display which renames would occur without performing them

$ rename -n ['s/foo/bar/'] [*]

Force renaming even if the operation would remove existing destination files

$ rename -f ['s/foo/bar/'] [*]

Convert filenames to lower case (use -f in case-insensitive filesystems to prevent "already exists" errors)

$ rename 'y/A-Z/a-z/' [*]

Replace whitespace with underscores

$ rename 's/\s+/_/g' [*]