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
Operating system	Unix and Unix-like
Type	Command
License	GNU GPL v3

History

The version of dirname bundled in GNU coreutils was written by David MacKenzie and Jim Meyering.[1]

Usage

The Single UNIX Specification for dirname is:

dirname string

string

A pathname

Examples

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 /
/

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.

See also

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

References

1. https://linux.die.net/man/1/dirname

External links

• dirname: return the directory portion of a pathname – Commands & Utilities Reference, The Single UNIX Specification, Issue 7 from The Open Group
• dirname(1) – Linux User Commands Manual
• dirname(1) – OpenBSD General Commands Manual