How do you sort a list of filepaths by the filename?

Question

I have the following list of files in a textfile named files.txt:

./themes/seven/images/list-item-rtl.png
./themes/seven/images/arrow-desc.png
./themes/seven/images/arrow-prev.png
./themes/seven/images/fc-rtl.png
./themes/seven/ie7.css
./xmlrpc.php
./MAINTAINERS.txt
./update.php
./README.txt
./COPYRIGHT.txt
./web.config

I want to sort them by just the filename (sort by the first characters after the last occurrence of the forward-slash). So the above would be output like so:

./COPYRIGHT.txt
./MAINTAINERS.txt
./README.txt
./themes/seven/images/arrow-desc.png
./themes/seven/images/arrow-prev.png
./themes/seven/images/fc-rtl.png
./themes/seven/ie7.css
./themes/seven/images/list-item-rtl.png
./update.php
./web.config
./xmlrpc.php

How do I do this?

Answer 1

$ awk -F '/' '{ printf "%s/%s\n", $NF, $0 }' files.txt | sort | cut -d '/' -f 2-
./COPYRIGHT.txt
./MAINTAINERS.txt
./README.txt
./themes/seven/images/arrow-desc.png
./themes/seven/images/arrow-prev.png
./themes/seven/images/fc-rtl.png
./themes/seven/ie7.css
./themes/seven/images/list-item-rtl.png
./update.php
./web.config
./xmlrpc.php

This prepends a copy the filename to the front of the line followed by a / character. The filename is had by taking the last /-delimited field. The last field is $NF in awk.

The output of the awk command is sorted. This sorting will use the /-delimited field added to the front of the line. cut is then used to remove the added /-delimited field.

This approach would work as long as no pathname contains a literal newline character.

There may also be an issue if any of the pathnames end with a / character (possibly the pathname of a directory). These would yield an empty string in the sorting column.

See also: Schwartzian transform

Answer 2

With GNU awk (gawk) one my specify array traversals:

awk -F'/' 'BEGIN {PROCINFO["sorted_in"] = "@ind_str_asc"} 
           { a[$NF]=$0 }
           END { for ( i in a ) { print a[i] } }' files.txt

In that case: load data into array, indices are defined by the last /-separated field (i.e. filename), elements are the lines of the file. Then traverse array sorted by index value for the printing step.

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Basic utils only:

paste <(rev files.txt | cut -d'/' -f 1 | rev) files.txt  | sort | cut -f2