dirname

The version of dirname bundled in GNU coreutils was written by David MacKenzie and Jim Meyering.[1] The command is available as a separate package for Microsoft Windows as part of the UnxUtils collection of native Win32 ports of common GNU Unix-like utilities.[2] The dirname command has also been ported to the IBM i operating system.[3]

The Single UNIX Specification for dirname is:

dirname string

string

A pathname

dirname will retrieve the directory-path name from a pathname ignoring any trailing slashes

$ dirname /home/martin/docs/base.wiki
/home/martin/docs

$ dirname /home/martin/docs/.
/home/martin/docs

$ dirname /home/martin/docs/
/home/martin

$ dirname base.wiki
.

$ dirname /
/

Since dirname accepts only one operand, its usage within the inner loop of shell scripts can be detrimental to performance. Consider

 while read file; do
     dirname "$file"
 done < some-input

The above excerpt would cause a separate process invocation for each line of input. For this reason, shell substitution is typically used instead

 echo "${file%/*}";

or if relative pathnames need to be handled as well

 if [ -n "${file##*/*}" ]; then
     echo "."
 else
     echo "${file%/*}";
 fi

Note that these handle trailing slashes differently than dirname.

We might think that paths that end in a trailing slash are a directory. But actually, the trailing slash represents all files within the directory.

/home/martin/docs/.

The correct way to represent a path as a directory is with a trailing slash and a period.

• List of Unix commands
• basename
• Path (computing)

The Wikibook Guide to Unix has a page on the topic of: Commands

• dirname: return the directory portion of a pathname – Shell and Utilities Reference, The Single UNIX Specification, Version 4 from The Open Group
• dirname(1) – Linux User Commands Manual
• dirname(1) – OpenBSD General Commands Manual