1 .\" Copyright (C) 1999 Andries Brouwer (aeb@cwi.nl)
3 .\" %%%LICENSE_START(VERBATIM)
4 .\" Permission is granted to make and distribute verbatim copies of this
5 .\" manual provided the copyright notice and this permission notice are
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8 .\" Permission is granted to copy and distribute modified versions of this
9 .\" manual under the conditions for verbatim copying, provided that the
10 .\" entire resulting derived work is distributed under the terms of a
11 .\" permission notice identical to this one.
13 .\" Since the Linux kernel and libraries are constantly changing, this
14 .\" manual page may be incorrect or out-of-date. The author(s) assume no
15 .\" responsibility for errors or omissions, or for damages resulting from
16 .\" the use of the information contained herein. The author(s) may not
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18 .\" which is licensed free of charge, as they might when working
21 .\" Formatted or processed versions of this manual, if unaccompanied by
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25 .\" Rewritten old page, 990824, aeb@cwi.nl
26 .\" 2004-12-14, mtk, added discussion of resolved_path == NULL
28 .TH REALPATH 3 2013-03-15 "" "Linux Programmer's Manual"
30 realpath \- return the canonicalized absolute pathname
33 .B #include <limits.h>
34 .B #include <stdlib.h>
36 .BI "char *realpath(const char *" path ", char *" resolved_path );
40 Feature Test Macro Requirements for glibc (see
41 .BR feature_test_macros (7)):
47 _BSD_SOURCE || _XOPEN_SOURCE\ >=\ 500 ||
48 _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED
53 expands all symbolic links and resolves references
57 characters in the null-terminated string named by
59 to produce a canonicalized absolute pathname.
60 The resulting pathname is stored as a null-terminated string,
64 in the buffer pointed to by
66 The resulting path will have no symbolic link,
74 is specified as NULL, then
78 to allocate a buffer of up to
80 bytes to hold the resolved pathname,
81 and returns a pointer to this buffer.
82 The caller should deallocate this buffer using
84 .\" Even if we use resolved_path == NULL, then realpath() will still
85 .\" return ENAMETOOLONG if the resolved pathname would exceed PATH_MAX
86 .\" bytes -- MTK, Dec 04
90 .\" function first appeared in 4.4BSD, contributed by Jan-Simon Pendry.
94 returns a pointer to the
97 Otherwise, it returns NULL, the contents
102 is set to indicate the error.
106 Read or search permission was denied for a component of the path prefix.
111 .\" (In libc5 this would just cause a segfault.)
112 (In glibc versions before 2.3,
113 this error is also returned if
118 An I/O error occurred while reading from the filesystem.
121 Too many symbolic links were encountered in translating the pathname.
124 A component of a pathname exceeded
126 characters, or an entire pathname exceeded
131 The named file does not exist.
134 A component of the path prefix is not a directory.
136 On Linux, this function appeared in libc 4.5.21.
138 4.4BSD, POSIX.1-2001.
140 POSIX.1-2001 says that the behavior if
142 is NULL is implementation-defined.
143 POSIX.1-2008 specifies the behavior described in this page.
145 In 4.4BSD and Solaris, the limit on the pathname length is
147 (found in \fI<sys/param.h>\fP).
152 as found in \fI<limits.h>\fP or provided by the
155 A typical source fragment would be
162 path_max = pathconf(path, _PC_PATH_MAX);
169 (But see the BUGS section.)
171 .\" 2012-05-05, According to Casper Dik, the statement about
172 .\" Solaris was not true at least as far back as 1997, and
173 .\" may never have been true.
175 .\" The 4.4BSD, Linux and SUSv2 versions always return an absolute
177 .\" Solaris may return a relative pathname when the
179 .\" argument is relative.
182 is given in \fI<unistd.h>\fP in libc4 and libc5,
183 but in \fI<stdlib.h>\fP everywhere else.
185 If the call fails with either
191 is not NULL, then the prefix of
193 that is not readable or does not exist is returned in
196 The POSIX.1-2001 standard version of this function is broken by design,
197 since it is impossible to determine a suitable size for the output buffer,
199 According to POSIX.1-2001 a buffer of size
203 need not be a defined constant, and may have to be obtained using
207 does not really help, since, on the one hand POSIX warns that
210 may be huge and unsuitable for mallocing memory,
211 and on the other hand
213 may return \-1 to signify that
217 .I "resolved_path\ ==\ NULL"
218 feature, not standardized in POSIX.1-2001,
219 but standardized in POSIX.1-2008, allows this design problem to be avoided.
221 The libc4 and libc5 implementation contained a buffer overflow
222 (fixed in libc-5.4.13).
223 Thus, set-user-ID programs like
225 needed a private version.
228 .BR canonicalize_file_name (3),
233 This page is part of release 3.65 of the Linux
236 A description of the project,
237 and information about reporting bugs,
239 \%http://www.kernel.org/doc/man\-pages/.