137 lines
3.8 KiB
Groff
137 lines
3.8 KiB
Groff
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.\"
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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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