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e2f6816100
Now that we've updated the prototypes of the basename(3) and dirname(3) functions to conform to POSIX, let's go ahead and reimplement dirname(3) in such a way that it's thread-safe, but also guaranteed to succeed. C libraries like glibc, musl and the one that's part of Solaris already follow such an approach. Move the existing implementation to another source file, freebsd11_dirname.c to keep existing users of the API that pass in a constant string happy, using symbol versioning. Put a new version of the function in dirname.c, obtained from CloudABI's C library. This version scans through the pathname string from left to right, normalizing it, while discarding the last pathname component. Reviewed by: emaste, jilles Differential Revision: https://reviews.freebsd.org/D7355
90 lines
2.4 KiB
Groff
90 lines
2.4 KiB
Groff
.\" $OpenBSD: dirname.3,v 1.17 2007/05/31 19:19:28 jmc Exp $
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.\"
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.\" Copyright (c) 1997 Todd C. Miller <Todd.Miller@courtesan.com>
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.\"
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.\" Permission to use, copy, modify, and distribute this software for any
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.\" purpose with or without fee is hereby granted, provided that the above
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.\" copyright notice and this permission notice appear in all copies.
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.\"
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.\" THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.\" MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
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.\" ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
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.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
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.\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
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.\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 12, 2016
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.Dt DIRNAME 3
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.Os
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.Sh NAME
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.Nm dirname
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.Nd extract the directory part of a pathname
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.Sh SYNOPSIS
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.In libgen.h
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.Ft char *
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.Fn dirname "char *path"
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.Sh DESCRIPTION
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The
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.Fn dirname
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function is the converse of
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.Xr basename 3 ;
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it returns a pointer to the parent directory of the pathname pointed to by
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.Fa path .
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Any trailing
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.Sq \&/
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characters are not counted as part of the directory
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name.
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.Sh RETURN VALUES
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If
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.Fa path
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is a null pointer, the empty string, or contains no
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.Sq \&/
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characters,
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.Fn dirname
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returns a pointer to the string
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.Qq \&. ,
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signifying the current directory.
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Otherwise,
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it returns a pointer to the parent directory of
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.Fa path .
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.Sh IMPLEMENTATION NOTES
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This implementation of
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.Fn dirname
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uses the buffer provided by the caller to store the resulting parent
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directory.
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Other vendor implementations may return a pointer to internal storage
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space instead.
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The advantage of the former approach is that it ensures thread-safety,
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while also placing no upper limit on the supported length of the
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pathname.
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.Pp
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The algorithm used by this implementation also discards redundant
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slashes and
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.Qq \&.
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pathname components from the pathname string.
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.Sh SEE ALSO
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.Xr basename 1 ,
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.Xr dirname 1 ,
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.Xr basename 3
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.Sh STANDARDS
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The
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.Fn dirname
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function conforms to
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.St -xpg4.2 .
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.Sh HISTORY
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The
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.Fn dirname
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function first appeared in
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.Ox 2.2
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and
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.Fx 4.2 .
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.Pp
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In
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.Fx 12.0 ,
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this function was reimplemented to store its result in the provided
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input buffer.
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.Sh AUTHORS
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.An Nuxi, the Netherlands
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