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33 .Nd make a relative path name from an absolute path name
36 .Fn abs2rel "const char *path" "const char *base" "char *result" "size_t size"
40 function makes a relative path name from an absolute path name
44 and copies the resulting path name into the memory referenced by
48 argument must refer to a buffer capable of storing at least
52 The resulting path name may include symbolic links.
55 function doesn't check whether or not any path exists.
59 function returns relative path name on success.
66 function may fail and set the external variable
68 to indicate the error.
73 directory isn't an absolute path name or the
79 argument is greater than zero but smaller than the length of the pathname plus 1.
81 char result[MAXPATHLEN];
82 char *path = abs2rel("/usr/src/sys", "/usr/local/lib", result, MAXPATHLEN);
86 path == "../../src/sys"
90 path1 = abs2rel("/usr/src/sys", "/usr", result, MAXPATHLEN);
91 path2 = abs2rel("/usr/src/sys", "/usr/src/sys", result, MAXPATHLEN);
101 directory includes symbolic links,
104 function produces the wrong path.
105 For example, if '/sys' is a symbolic link to '/usr/src/sys',
107 char *path = abs2rel("/usr/local/lib", "/sys", result, MAXPATHLEN);
111 path == "../usr/local/lib" /* It's wrong!! */
113 You should convert the base directory into a real path in advance.
116 path = abs2rel("/sys/kern", realpath("/sys", resolvedname), result, MAXPATHLEN);
120 path == "../../../sys/kern" /* It's correct but ... */
122 That is correct, but a little redundant. If you wish get the simple
123 answer 'kern', do the following.
125 path = abs2rel(realpath("/sys/kern", r1), realpath("/sys", r2),
130 function assures correct result, but don't forget that
132 requires that all but the last component of the path exist.
136 Shigio Yamaguchi (shigio@tamacom.com)