dirname is a
shell
Shell may refer to:
Architecture and design
* Shell (structure), a thin structure
** Concrete shell, a thin shell of concrete, usually with no interior columns or exterior buttresses
Science Biology
* Seashell, a hard outer layer of a marine ani ...
command
Command may refer to:
Computing
* Command (computing), a statement in a computer language
* command (Unix), a Unix command
* COMMAND.COM, the default operating system shell and command-line interpreter for DOS
* Command key, a modifier key on A ...
for extracting the
directory path portion of a
path
A path is a route for physical travel – see Trail.
Path or PATH may also refer to:
Physical paths of different types
* Bicycle path
* Bridle path, used by people on horseback
* Course (navigation), the intended path of a vehicle
* Desir ...
; without the last name. The command is specified in the
Single UNIX Specification
The Single UNIX Specification (SUS) is a standard for computer operating systems, compliance with which is required to qualify for using the "UNIX" trademark. The standard specifies programming interfaces for the C language, a command-line shell, ...
and is primarily used in
shell script
A shell script is a computer program designed to be run by a Unix shell, a command-line interpreter. The various dialects of shell scripts are considered to be command languages. Typical operations performed by shell scripts include file manipu ...
s.
The version in
GNU Core Utilities
The GNU Core Utilities or coreutils is a collection of GNU software that implements many standard, Unix-based shell commands. The utilities generally provide POSIX compliant interface when the environment variable is set, but otherwise offers ...
was written by David MacKenzie and Jim Meyering. The command is available for
Windows
Windows is a Product lining, product line of Proprietary software, proprietary graphical user interface, graphical operating systems developed and marketed by Microsoft. It is grouped into families and subfamilies that cater to particular sec ...
via
UnxUtils
UnxUtils is a collection of utility programs that provide popular Unix-based shell commands ported from GNU implementations as native Windows programs that depend only on Win32 and the Microsoft C- runtime ( msvcrt.dll). The collection wa ...
, and is in
IBM i
IBM i (the ''i'' standing for ''integrated'') is an operating system developed by IBM for IBM Power Systems. It was originally released in 1988 as OS/400, as the sole operating system of the IBM AS/400 line of systems. It was renamed to i5/OS in 2 ...
.
Usage
The
Single UNIX Specification
The Single UNIX Specification (SUS) is a standard for computer operating systems, compliance with which is required to qualify for using the "UNIX" trademark. The standard specifies programming interfaces for the C language, a command-line shell, ...
is: .
Examples
The command reports the directory path portion of a path ignoring any trailing slashes.
$ dirname /home/martin/docs/base.wiki
/home/martin/docs
$ dirname /home/martin/docs/
/home/martin
$ dirname base.wiki
.
Performance
Since the command accepts only one operand, its usage within the
inner loop
In computer programs, an important form of control flow is the Loop (computing), loop which causes a block of code to be executed more than once. A common idiom is to have a loop Nested loop, nested inside another loop, with the contained loop be ...
of a shell script can be detrimental to performance. Consider:
while read file; do
dirname "$file"
done < some-input
The above causes a separate process invocation for each line of input. For this reason, shell substitution is typically used instead
echo "$";
Or, if relative pathnames need to be handled as well:
if -n "$" then
echo "."
else
echo "$";
fi
Note that these handle trailing slashes differently than .
See also
*
*
References
External links
*
*
*
{{Core Utilities commands
Dirname
Unix SUS2008 utilities
IBM i Qshell commands