[SOLVED] [bash] rm regular expression help

RaptorX · 07-31-2009, 02:12 PM

I am having troubles with regular expressions...

I read the beginners guide to regex from here: [http://tldp.org/LDP/Bash-Beginners-G...l/chap_04.html]

But there is something evading me!

I want to learn in general but there is a particular problem that i want to solve:

I have a folder in which i will put my trash and when i exit bash i will delete the contents of that folder except two folders, so i have something like this right now:

[files]
[info]
temp1
temp2
temp3

doing some testing i get to this:

Code:

[~/.trash]$ rm $TRASH/*[!files]
rm: cannot remove `~/.trash//info': Is a directory

so basically [!expression] is a negation and the folder [files] is not being counted by rm.

now if I try:

Code:

[~/.trash]$ rm $TRASH/*[!files][!info]
rm: cannot remove `/home/.Trash-1000//*[!files][!info]': No such file or directory

[~/.trash]$ rm $TRASH/*[!files] [!info]
rm: cannot remove `~/.trash//info': Is a directory
rm: cannot remove `[!info]': No such file or directory

[~/.trash]$ rm $TRASH/*[!files] *[!info]
rm: cannot remove `~/.trash//info': Is a directory
rm: cannot remove `files': Is a directory

so I guess the question that i should be asking is:

How do i exclude *several* files or folders from being deleted?

Note that i could use "find -type f" to help me out but in general my trash can be files OR folders so I do want to remove other folders but not those two.

GrapefruiTgirl · 07-31-2009, 02:21 PM

Looks to me like (in the first & 4th examples) you are going about it the right way. Check out the man page for rm for further details, particularly the -f and -R switches, which will cause your commands to act on folders. By default, rm works on files, not folders, and especially not folders with stuff in them. (I stand to be corrected on the semantics here, but this is what my experience has shown).

Also, FWIW, you have an extra slash in there, probably because you added it to the end of the $TRASH variable.

Sasha

catkin · 07-31-2009, 02:23 PM

Hello RaptorX

Too many "regular expressions" on *n*x systems!

That link is to regular expressions as used by grep and others. The expression in

Code:

[~/.trash]$ rm $TRASH/*[!files]

is a file name expansion as explained at http://www.gnu.org/software/bash/man...name-Expansion.

Maybe that's enough to point you in the right direction. Meanwhile I'll think about the job could be done and post again later.

Best

Charles

RaptorX · 07-31-2009, 02:33 PM

thanks for the quick replays guys...

@GrapefruiTgirl

right now im just testing, I plan to do a rm -rf soon but if i do it now i WILL remove the folders [info] and [files] which already have some info that i dont want to mess up... I know... move them out and try with dummy folders...

I was just lazy...

Quote:

Also, FWIW, you have an extra slash in there, probably because you added it to the end of the $TRASH variable.

it is true... I will fix that.

thanks for that I was already wondering a little time ago but didnt think about that.

@catkin

you are correct, that file was talking about grep in particular... I was finding it bit strange that some expressions did not work on other commands so I tried to figure out myself but I figure out that it would take a lot of time... (reading man bash at the moment, which can cause an aneurysm in the brain very quickly!!) i will take a time and read what you sent me.

catkin · 07-31-2009, 02:39 PM

This works

Code:

find . -name './\[files\]' -prune -o -name '\[info\]' -prune -o -exec echo rm -fr {} \;

The backslashes are necessary because [<stuff>] is a regular expression term for find.

Edit: actually is doesn't work unless the echo is removed (once you are confident it is generating the right commads)!

RaptorX · 07-31-2009, 02:42 PM

interesting...

[can you tell me what -prune and -o means?]
I dont like to simply copy/paste things.

[EDIT: never mind im reading find --help]

EDIT2: sorry i dont find a definition for -prune, can you explain me what it does in this particular example?

catkin · 07-31-2009, 02:49 PM

And this produces a list of all the files-and-directories you want to delete using extended globbing (globbing is another, delightful, term for file name expansion)

Code:

shopt -s extglob
echo !('[files]'|'[info]')

RaptorX · 07-31-2009, 02:51 PM

Thanks for the help I ended up with

Code:

find $TRASH ! -name 'files' -a ! -name 'info' -exec rm -rf {} \;

which works exactly as i need.

RaptorX · 07-31-2009, 02:53 PM

Quote:

Originally Posted by catkin

And this produces a list of all the files-and-directories you want to delete using extended globbing (globbing is another, delightful, term for file name expansion)

Code:

shopt -s extglob
echo !('[files]'|'[info]')

actually yes!
I was reading about it but I had a question that i couldnt find the answer...

do i have to initialize shopt -s extglob every time i start bash or is it a 1 time command?

if i have to initialize it then i guess i can put it in .bashrc

catkin · 07-31-2009, 02:56 PM

Quote:

Originally Posted by RaptorX

EDIT2: sorry i dont find a definition for -prune, can you explain me what it does in this particular example?

The man page is not easy to understand about -prune (best description under the explanation of -wholename). It stops "find" from processing the directory just matched -- no further action is taken on that directory and files-and-directories in it are not examined.

catkin · 07-31-2009, 02:59 PM

Quote:

Originally Posted by RaptorX

Thanks for the help I ended up with

Code:

find $TRASH ! -name 'files' -a ! -name 'info' -exec rm -rf {} \;

which works exactly as i need.

So the directories were not called [files] and [info], that was just the formatting you were using to denote them as directories? Hah! Not a convention I have seen before ... where is it from?

catkin · 07-31-2009, 03:02 PM

Quote:

Originally Posted by RaptorX

actually yes!
I was reading about it but I had a question that i couldnt find the answer...

do i have to initialize shopt -s extglob every time i start bash or is it a 1 time command?

if i have to initialize it then i guess i can put it in .bashrc

Every time, unless you put it in one of the shell initialisation files like ~/bashrc. Downside of doing that is any scripts written assuming it is set and using extended globbing will fail if it is not set, so you may prefer to set it explicitly when you need it rather than putting it in a shell initialisation file.

catkin · 07-31-2009, 03:05 PM

Quote:

Originally Posted by RaptorX

Thanks for the help I ended up with

Code:

find $TRASH ! -name 'files' -a ! -name 'info' -exec rm -rf {} \;

which works exactly as i need.

It will delete the contents of the files/ and info/ directories. OK?

RaptorX · 07-31-2009, 03:08 PM

hahaha that with the folders was just my doing, nothing copied...

so if i do not specify -prune even though i said to "find" do not match [files] it will still delete what is inside of that folder?? why on earth? where is the logic on that?

EDIT: it is true... I just tested the command and it does not list the folder [files] but it does list everything what is inside that folder... go figure.

RaptorX · 07-31-2009, 03:17 PM

when i used the -prune option it doesnt list anything...

im trying:

Code:

find $TRASH ! -name 'files' -prune -a ! -name 'info' -prune -exec echo {} \;