xref: /freebsd/lib/libc/gen/dirname.3 (revision e2f68161004f312bf10e4b683ac866b45f6e8489)

.\" $OpenBSD: dirname.3,v 1.17 2007/05/31 19:19:28 jmc Exp $
.\"
.\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.\" $FreeBSD$
.\"
.Dd August 12, 2016
.Dt DIRNAME 3
.Os
.Sh NAME
.Nm dirname
.Nd extract the directory part of a pathname
.Sh SYNOPSIS
.In libgen.h
.Ft char *
.Fn dirname "char *path"
.Sh DESCRIPTION
The
.Fn dirname
function is the converse of
.Xr basename 3 ;
it returns a pointer to the parent directory of the pathname pointed to by
.Fa path .
Any trailing
.Sq \&/
characters are not counted as part of the directory
name.
.Sh RETURN VALUES
If
.Fa path
is a null pointer, the empty string, or contains no
.Sq \&/
characters,
.Fn dirname
returns a pointer to the string
.Qq \&. ,
signifying the current directory.
Otherwise,
it returns a pointer to the parent directory of
.Fa path .
.Sh IMPLEMENTATION NOTES
This implementation of
.Fn dirname
uses the buffer provided by the caller to store the resulting parent
directory.
Other vendor implementations may return a pointer to internal storage
space instead.
The advantage of the former approach is that it ensures thread-safety,
while also placing no upper limit on the supported length of the
pathname.
.Pp
The algorithm used by this implementation also discards redundant
slashes and
.Qq \&.
pathname components from the pathname string.
.Sh SEE ALSO
.Xr basename 1 ,
.Xr dirname 1 ,
.Xr basename 3
.Sh STANDARDS
The
.Fn dirname
function conforms to
.St -xpg4.2 .
.Sh HISTORY
The
.Fn dirname
function first appeared in
.Ox 2.2
and
.Fx 4.2 .
.Pp
In
.Fx 12.0 ,
this function was reimplemented to store its result in the provided
input buffer.
.Sh AUTHORS
.An Nuxi, the Netherlands