Dirname

dirname is a standard computer program on Unix and Unix-like operating systems. When dirname is given a pathname, it will delete any suffix beginning with the last slash ('/') character and return the result. dirname is described in the Single UNIX Specification and is primarily used in shell scripts.

dirname

Example of dirname command
Developer(s)	Various open-source and commercial developers
Operating system	Unix, Unix-like, IBM i
Platform	Cross-platform
Type	Command
License	coreutils: GPLv3+

History

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]

Usage

The Single UNIX Specification for dirname is:

dirname string

string

A pathname

$ 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 / /

Performance

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.

Misconceptions

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.^{[according to whom?][citation needed]}

See also

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

References

1. "Dirname(1) - Linux man page".
2. "Native Win32 ports of some GNU utilities". unxutils.sourceforge.net.
3. IBM. "IBM System i Version 7.2 Programming Qshell" (PDF). IBM. Archived (PDF) from the original on 2020-09-18. Retrieved 2020-09-05.

External links

• 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