Re: [PATCH] filter ls output by filetype (original) (raw)

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From: Pádraig Brady
Subject: Re: [PATCH] filter ls output by filetype
Date: Thu, 28 Nov 2013 14:09:10 +0000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2

On 11/28/2013 01:49 PM, Hal Ashburner wrote:

ls filters by filename - leading dot -a -A or --ignore pattern I have shell script that just shows directories by interposing test between two calls to ls in a pipeline to give me ls like behavior. Ls actually knows the filetype so I thought why not just filter on it in ls given filtering is something ls does? I noted this was not a rejected feature request and thought it might go well as a request accompanied by a patch.

--just was the best switch I could think of to achieve this end. I could easily be convinced there exists a better one. (--show-only? --showing?)

examples: just list the block device files

./ls --just b /dev loop0 loop3 loop6 ram1 ram12 ram15 ram4 ram7 sda sda3 sda6 sda9 loop1 loop4 loop7 ram10 ram13 ram2 ram5 ram8 sda1 sda4 sda7 sdb loop2 loop5 ram0 ram11 ram14 ram3 ram6 ram9 sda2 sda5 sda8

./ls --just=normal ABOUT-NLS config.log NEWS aclocal.m4 config.status README AUTHORS configure README-hacking bootstrap configure.ac <http://configure.ac> README-package-renamed-to-coreutils bootstrap.conf COPYING README-prereq cfg.mk <http://cfg.mk> dist-check.mk <http://dist-check.mk> README-release ChangeLog HACKING README-valgrind ChangeLog-2005 init.cfg thanks-gen ChangeLog-2006 Makefile THANKS.in ChangeLog-2007 Makefile.am THANKStt.in ChangeLog-2008 Makefile.in TODO

can filter on two types by applying the switch twice.

./src/ls --just=normal --just=symbolic-links -l test total 0 lrwxrwxrwx 1 hal hal 13 Nov 29 00:20 link-to-somefile -> test/somefile -rw-rw-r-- 1 hal hal 0 Nov 29 00:20 somefile

Why might rejection of this feature and patch be a good idea? You can get this kind of thing done (sort of) with $ find . -type d --maxdepth=1 -ls or shell globbing abuse eg $ ls -d */ but obviously such things are not ls and lose the familiar and consistent ls options such as find displaying a differing long format, no colored output, sorting, control of display of dotfiles etc. However all of these alternatives' shortcomings can be alleviated with fairly ordinary shell pipelines involving sed and/or test at the cost of a simple, robust and convenient user interface as provided by ls.

Shortcomings/BUGS/Possible future enhancements : 1) doesn't work with -R for anything except directories 2) Doesn't have a mode to filter based on permissions (eg show only executables or setuid etc). 3) Doesn't follow symbolic links and then filter them based on the type of file they are pointing at and I haven't yet worked out how to add the command interface for "including symlinks to" in a way that is not too ugly. 4) Others that exist of which I haven't considered.

3 at least would be handled by filtering outside ls, by leveraging the --classify option.

ls --color -lF | sed -n 's#/$##p'

On the off chance that there does happen to be interest in this feature and patch by coreutils hackers, I am more than happy to assign the copyright to GNU on the understanding it will be published under the appropriate version of the GPL for coreutils. The patch should apply cleanly to the current default git checkout. I'm subscribed to the list and interested in any and all feedback.

Thank you for taking the time to give this request an appropriate level of consideration.

Thanks for taking the time to do the patch. However the bar is high for new options to ls, and I'm not sure this provides enough benefit. I'd be 60:40 against adding it.

thanks, Pádraig.