17.17 Lowercase Filenames

20200915 There are times when we have a directory of files with some confused mixture of uppercase and lowercase names. On GNU/Linux the case of a filename is significant and thus we need to know how the precise capitalisation of a name in order to find a file. As a tradition filenames on Linux are typically all lowercase though today we also see mixed case filenames quite commonly. Non-the-less there are times when we may like to lowercase our filenames.

$ ls
Lemon_Squeeze_Track_01_Juice.abc
Lemon_Squeeze_Track_02_Justice-and-Penalty.abc
Lemon_Squeeze_Track_03_Junior-and-Petite.abc
Lemon_Squeeze_TRACK_04_Jump-and-Pan.abc
...

We use rename with the transliteration operator y to lowercase the names of all files in the current directory. The y operator translates from one sequence of characters to another. The -n is short for --nono and will report what the command would do but not actually do it. The wildcard for the filename argument (*) will expand to all files in the current directory but rename will only operate on those files whose filename matches the transformation string.

$ rename -n 'y/A-Z/a-z/' *
rename(Lemon_Squeeze_Track_01_Juice.abc, lemon_squeeze_track_01_juice.abc)
rename(Lemon_Squeeze_Track_02_Justice-and-Penalty.abc, lemon_squeeze_track_02_j...
rename(Lemon_Squeeze_Track_03_Junior-and-Petite.abc, lemon_squeeze_track_03_jun...
rename(Lemon_Squeeze_TRACK_04_Jump-and-Pan.abc, lemon_squeeze_track_04_jump-and...
...

If the promise is correct then we can execute the command, using -v, short for --verbose, in case a mistake is made. If a mistake is made can copy the verbose output into a script file and effectively create a script to undo the renaming.

$ rename -v 'y/A-Z/a-z/' *
Lemon_Squeeze_Track_01_Juice.abc renamed as lemon_squeeze_track_01_juice.abc
Lemon_Squeeze_Track_02_Justice-and-Penalty.abc renamed as lemon_squeeze_track_0...
Lemon_Squeeze_Track_03_Junior-and-Petite.abc renamed as lemon_squeeze_track_03_...
Lemon_Squeeze_TRACK_04_Jump-and-Pan.abc renamed as lemon_squeeze_track_04_jump-...
...

Our result is then a directory of files with all lowercase filenames.

$ ls
lemon_squeeze_track_01_jusice.abc
lemon_squeeze_track_02_justice-and-penalty.abc
lemon_squeeze_track_03_junior-and-petite.abc
lemon_squeeze_track_04_jump-and-pan.abc
...


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