Bash rename last underscore in string

Question

I have got a directory with files in which some of then end with an underscore.

I would like to test each file to see if it ends with an underscore and then strip off the underscore.

I am currently running the following code:

for file in *;do
   echo $file;
   if [[  "${file:$length:1}" == "_"   ]];then 
       mv $file  $(echo $file | sed "s/.$//g");
   fi
done

But it does not seem to be renaming the files with underscore. For example if i have a file called all_indoors_ I expect it to give me all_indoors.

Do you just want to remove the underscore, nothing else? Also, where is `$length` defined? — fedorqui, Dec 28 '15 at 12:04
What do you mean with *strip off*? Remove the underscore, or the underscore and the remaining text? — Willem Van Onsem, Dec 28 '15 at 12:08
strip off. I meant remove the underscore as noted on the example. all_indoors_ should be renamed all_indoors — kartoza-geek, Dec 28 '15 at 12:11
@kartoza-geek: yes but say the file is `foo_bar`, should it be renamed to `foobar`, or `foo`? — Willem Van Onsem, Dec 28 '15 at 12:12
if file is foo_bar it should not be renamed. Only when it's foor_bar_ should it be renamed. Hence the need to check the last string if is an underscore — kartoza-geek, Dec 28 '15 at 12:15

Eugene Yarmash · Answer 1 · 2015-12-28T12:19:47.193

1

You could use built-in string substitution:

for file in *_; do
    mv "$file" "${file%_}"
done

edited Dec 28 '15 at 12:19

answered Dec 28 '15 at 12:05

Eugene Yarmash

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score 1 · Answer 2 · edited May 23 '17 at 11:59

1

Just use a regex to check the string:

for file in *
do
   [[ $file =~ "_$" ]] && echo mv "$file" "${file%%_}"
done

Once you are sure it works as intended, remove the echo so that the mv command executes!

It may even be cleaner to use *_ so that the for will just loop over the files with a name ending with _, as hek2mgl suggests in comments.

for file in *_
do
   echo mv "$file" "${file%%_}"
done

edited May 23 '17 at 11:59

Community

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answered Dec 28 '15 at 12:11

fedorqui

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I like this answer, but why not using `for file in *_` ? This would save you the regex check. – hek2mgl Dec 28 '15 at 12:15
@hek2mgl yours is the most clever approach here : ) I haven't thought about it, updating my answer with it! (Or feel free to add your own answer, of course). – fedorqui Dec 28 '15 at 12:17
1

No, no.. Go for it! :) – hek2mgl Dec 28 '15 at 12:17
2

@hek2mgl nice - fedorqui: quote the arguments to move to support files with spaces as in: for i in *\_; do echo mv "$i" "${i%_}"; done – Julian Dec 28 '15 at 12:20
You probably don't need another `%` (there's no longer match) – Eugene Yarmash Dec 28 '15 at 12:21
@eugeney But there is also no shorter match! ;) I mean it doesn't matter. – hek2mgl Dec 28 '15 at 12:21
@Julian yes. Updated to make it more explicit (I couldn't quote again within the `echo` statement) – fedorqui Dec 28 '15 at 12:23
You don't have to - prepending the echo in front of the mv as I've shown in my previous comment will work without putting any additional quotes in – Julian Dec 28 '15 at 12:26

score 0 · Accepted Answer · answered Dec 28 '15 at 12:07

0

You can use which will be recursive:

while read f; do 
  mv "$f" "${f:0:-1}"; # Remove last character from $f
done < <(find . -type f -name '*_')

answered Dec 28 '15 at 12:07

Andreas Louv

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This would break if there are newlines in the file names. I suggest to loop over the glob instead of using find here. – hek2mgl Dec 28 '15 at 12:11

Willem Van Onsem · Answer 4 · 2015-12-28T15:58:14.017

0

Although not a pure bash approach, you can use rename.ul (written by Larry Wall, the person behind perl). Rename is not part of the default linux environment, but is part of util-linux.

You use rename with:

rename perlexpr files

(some flags ommitted).

So you could use:

rename 's/_$//' *

if you want to remove all characters including and after the underscore.

As @hek2mgl points out, there are multiple rename commands (see here), so first test if you have picked the right one.

edited Dec 28 '15 at 15:58

answered Dec 28 '15 at 12:09

Willem Van Onsem

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The `rename` command from util-linux is *not* capable of perl regular expressions! (I also needed to realize that... ;) ) – hek2mgl Dec 28 '15 at 12:13
@hek2mgl: then why does the documentation specifies so? – Willem Van Onsem Dec 28 '15 at 12:20
If your `man rename` says so, it is not from `util-linux`. What does `rename -V` give you? `rename from util-linux 2.26.2` ? I guess you are referring to http://search.cpan.org/dist/rename/ . Nice tool! But unfortunately not part of `util-linux`. – hek2mgl Dec 28 '15 at 12:23
@hek2mgl: only `Usage: rename [-v] [-n] [-f] perlexpr [filenames]`. Perhaps I've installed two versions of `rename` fighting with each other... – Willem Van Onsem Dec 28 '15 at 12:25
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To complete the confusion, there also a BSD version available! :) `rename` is a nice tool, but unfortunately it is not portable so far. – hek2mgl Dec 28 '15 at 12:26
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@hek2mgl: well let's agree that in order to remove an underscore, one does not niet *Perlish* powers. (Furthermore I went to FOSDEM last year, and Larry Wall said in his talk that the new Perl regexes would have less representation power, simply because they tend to be error-prone). – Willem Van Onsem Dec 28 '15 at 12:28
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Well, but `rename` from util-linux doesn't support regular expressions at all. It supports only fixed strings. It's really pretty basic. – hek2mgl Dec 28 '15 at 12:36
@hek2mgl: I've updated the answer with a less ambiguous reference to `rename`. – Willem Van Onsem Dec 28 '15 at 15:58
1

If you also remove the sentence that says that Larry Wall's version of `rename` belongs to `util-linux` I'm fine with it. :) – hek2mgl Dec 28 '15 at 16:18

Bash rename last underscore in string

4 Answers4