0f7f3352c8
It allows one to trivially convert an absolute path to a relative path and the reverse. The test programs themselves are very useful in scripts but the real use comes shortly with the -r and -a arguments to ln. These are sometimes known as the --relative and --absolute flags and can force a symlink to be relative when you only have an absolue path. Another place these are sometimes used is to add -a and -r args to 'realpath'. Incredibly useful in Makefiles. I was going to just add the files in with 'ln' but a library makes more sense. The test programs may come out in their own right some day for scripting. released under a BSD 2-clause: * Copyright (c) 1997 Shigio Yamaguchi. All rights reserved. * Copyright (c) 1999 Tama Communications Corporation. All rights reserved. The test directry does not conform to any framework. Not connected to build. doc people may want to play with the manual pages. Obtained from: https://www.tamacom.com/pathconvert.html Shigio Yamaguchi. MFC after: 1 month Relnotes: yes Sponsored by: Panzura, Tama Communications Corporation
137 lines
3.8 KiB
Groff
137 lines
3.8 KiB
Groff
.\"
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.\" Copyright (c) 1997 Shigio Yamaguchi. All rights reserved.
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.\" Copyright (c) 1999 Tama Communications Corporation. All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd Dec 15, 1997"
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.Dt ABS2REL 3
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.Os
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.Sh NAME
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.Nm abs2rel
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.Nd make a relative path name from an absolute path name
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.Sh SYNOPSIS
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.Ft "char *"
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.Fn abs2rel "const char *path" "const char *base" "char *result" "size_t size"
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.Sh DESCRIPTION
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The
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.Fn abs2rel
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function makes a relative path name from an absolute path name
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.Fa path
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based on a directory
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.Fa base
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and copies the resulting path name into the memory referenced by
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.Fa result .
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The
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.Fa result
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argument must refer to a buffer capable of storing at least
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.Fa size
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characters.
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The resulting path name may include symbolic links.
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The
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.Fn abs2rel
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function doesn't check whether or not any path exists.
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.Sh "RETURN VALUES"
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The
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.Fn abs2rel
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function returns relative path name on success.
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If an error occurs,
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it returns
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.Dv NULL .
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.Sh ERRORS
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The
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.Fn abs2rel
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function may fail and set the external variable
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.Va errno
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to indicate the error.
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.Bl -tag -width Er
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.It Bq Er EINVAL
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The
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.Fa base
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directory isn't an absolute path name or the
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.Fa size
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argument is zero.
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.It Bq Er ERANGE
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The
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.Fa size
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argument is greater than zero but smaller than the length of the pathname plus 1.
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.Sh EXAMPLE
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char result[MAXPATHLEN];
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char *path = abs2rel("/usr/src/sys", "/usr/local/lib", result, MAXPATHLEN);
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yields:
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path == "../../src/sys"
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Similarly,
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path1 = abs2rel("/usr/src/sys", "/usr", result, MAXPATHLEN);
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path2 = abs2rel("/usr/src/sys", "/usr/src/sys", result, MAXPATHLEN);
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yields:
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path1 == "src/sys"
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path2 == "."
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.Sh BUGS
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If the
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.Fa base
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directory includes symbolic links,
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the
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.Fn abs2rel
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function produces the wrong path.
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For example, if '/sys' is a symbolic link to '/usr/src/sys',
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char *path = abs2rel("/usr/local/lib", "/sys", result, MAXPATHLEN);
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yields:
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path == "../usr/local/lib" /* It's wrong!! */
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You should convert the base directory into a real path in advance.
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.Pp
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path = abs2rel("/sys/kern", realpath("/sys", resolvedname), result, MAXPATHLEN);
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yields:
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path == "../../../sys/kern" /* It's correct but ... */
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That is correct, but a little redundant. If you wish get the simple
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answer 'kern', do the following.
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path = abs2rel(realpath("/sys/kern", r1), realpath("/sys", r2),
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result, MAXPATHLEN);
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The
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.Fn realpath
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function assures correct result, but don't forget that
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.Fn realpath
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requires that all but the last component of the path exist.
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.Sh "SEE ALSO"
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.Xr rel2abs 3
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.Sh AUTHORS
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Shigio Yamaguchi (shigio@tamacom.com)
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