basename dirname | Almost every UNIX command can use relative and absolute pathnames (14.2) to find a file or directory. There are times you'll need part of a pathname - the head (everything before the last slash) or the tail (the name after the last slash). The utilities basename and dirname, available on most UNIX systems (and on the CD-ROM) handle that. |
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The basename command strips any "path" name components from a filename, leaving you with a "pure" filename. For example:
%basename /usr/bin/gigiplot
gigiplot %basename /home/mikel/bin/bvurns.sh
bvurns.sh
basename can also strip a suffix from a filename. For example:
%basename /home/mikel/bin/bvurns.sh .sh
bvurns
The dirname command strips the filename itself, giving you the "directory" part of the pathname:
%dirname /usr/bin/screenblank
/usr/bin %dirname local
.
If you give dirname a "pure" filename (i.e., a filename with no
path, as in the second example), it tells you that the directory is
.
(the current directory).
NOTE: dirname and basename have a bug in many System V implementations. They don't recognize the second argument as a filename suffix to strip. Here's a good test:
%basename 0.foo .foo
If the answer is
0
, your basename implementation is good. If the answer is0.foo
, the implementation is bad. If basename doesn't work, dirname won't, either.
Here's an example of basename and dirname.
There's a directory tree with some very large files - over 100,000
characters.
You want to find those files, run
split (35.9)
on them, and add huge. to the start of the original filename.
By default, split names the file chunks xaa, xab,
xac, and
so on; you want to use the original filename and a dot (.
)
instead of x:
|| exit | for path in `find /home/you -type f -size +100000c -print` do cd `dirname $path` || exit filename=`basename $path` split $filename $filename. mv -i $filename huge.$filename done |
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The find command will output pathnames like these:
/home/you/somefile /home/you/subdir/anotherfile
(The absolute pathnames are important here. The cd would fail on the second pass of the loop if you use relative pathnames.) In the loop, the cd command uses dirname to go to the directory where the file is. The filename variable, with the output of basename, is used several places - twice on the split command line.
If that gives the error command line too long
, replace the first
lines with the two lines below.
This makes a
redirected-input loop (45.22):
find /home/you -type f -size +100000c -print | while read path
-
,