.\" Copyright (C) 1999 Andries Brouwer (aeb@cwi.nl) .\" .\" %%%LICENSE_START(VERBATIM) .\" Permission is granted to make and distribute verbatim copies of this .\" manual provided the copyright notice and this permission notice are .\" preserved on all copies. .\" .\" Permission is granted to copy and distribute modified versions of this .\" manual under the conditions for verbatim copying, provided that the .\" entire resulting derived work is distributed under the terms of a .\" permission notice identical to this one. .\" .\" Since the Linux kernel and libraries are constantly changing, this .\" manual page may be incorrect or out-of-date. The author(s) assume no .\" responsibility for errors or omissions, or for damages resulting from .\" the use of the information contained herein. The author(s) may not .\" have taken the same level of care in the production of this manual, .\" which is licensed free of charge, as they might when working .\" professionally. .\" .\" Formatted or processed versions of this manual, if unaccompanied by .\" the source, must acknowledge the copyright and authors of this work. .\" %%%LICENSE_END .\" .\" Rewritten old page, 990824, aeb@cwi.nl .\" 2004-12-14, mtk, added discussion of resolved_path == NULL .\" .TH REALPATH 3 2017-09-15 "" "Linux Programmer's Manual" .SH NAME realpath \- return the canonicalized absolute pathname .SH SYNOPSIS .nf .B #include .B #include .PP .BI "char *realpath(const char *" path ", char *" resolved_path ); .fi .PP .in -4n Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .in .PP .BR realpath (): .ad l .RS 4 _XOPEN_SOURCE\ >=\ 500 .\" || _XOPEN_SOURCE\ &&\ _XOPEN_SOURCE_EXTENDED || /* Glibc since 2.19: */ _DEFAULT_SOURCE || /* Glibc versions <= 2.19: */ _BSD_SOURCE .RE .ad .SH DESCRIPTION .BR realpath () expands all symbolic links and resolves references to .IR "/./" ", " "/../" and extra \(aq/\(aq characters in the null-terminated string named by .I path to produce a canonicalized absolute pathname. The resulting pathname is stored as a null-terminated string, up to a maximum of .B PATH_MAX bytes, in the buffer pointed to by .IR resolved_path . The resulting path will have no symbolic link, .I "/./" or .I "/../" components. .PP If .I resolved_path is specified as NULL, then .BR realpath () uses .BR malloc (3) to allocate a buffer of up to .B PATH_MAX bytes to hold the resolved pathname, and returns a pointer to this buffer. The caller should deallocate this buffer using .BR free (3). .\" Even if we use resolved_path == NULL, then realpath() will still .\" return ENAMETOOLONG if the resolved pathname would exceed PATH_MAX .\" bytes -- MTK, Dec 04 .\" .SH HISTORY .\" The .\" .BR realpath () .\" function first appeared in 4.4BSD, contributed by Jan-Simon Pendry. .SH RETURN VALUE If there is no error, .BR realpath () returns a pointer to the .IR resolved_path . .PP Otherwise, it returns NULL, the contents of the array .I resolved_path are undefined, and .I errno is set to indicate the error. .SH ERRORS .TP .B EACCES Read or search permission was denied for a component of the path prefix. .TP .B EINVAL .I path is NULL. .\" (In libc5 this would just cause a segfault.) (In glibc versions before 2.3, this error is also returned if .IR resolved_path is NULL.) .TP .B EIO An I/O error occurred while reading from the filesystem. .TP .B ELOOP Too many symbolic links were encountered in translating the pathname. .TP .B ENAMETOOLONG A component of a pathname exceeded .B NAME_MAX characters, or an entire pathname exceeded .B PATH_MAX characters. .TP .B ENOENT The named file does not exist. .TP .B ENOMEM Out of memory. .TP .B ENOTDIR A component of the path prefix is not a directory. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lb lb lb l l l. Interface Attribute Value T{ .BR realpath () T} Thread safety MT-Safe .TE .SH CONFORMING TO 4.4BSD, POSIX.1-2001. .PP POSIX.1-2001 says that the behavior if .I resolved_path is NULL is implementation-defined. POSIX.1-2008 specifies the behavior described in this page. .SH NOTES In 4.4BSD and Solaris, the limit on the pathname length is .B MAXPATHLEN (found in \fI\fP). SUSv2 prescribes .B PATH_MAX and .BR NAME_MAX , as found in \fI\fP or provided by the .BR pathconf (3) function. A typical source fragment would be .PP .in +4n .EX #ifdef PATH_MAX path_max = PATH_MAX; #else path_max = pathconf(path, _PC_PATH_MAX); if (path_max <= 0) path_max = 4096; #endif .EE .in .PP (But see the BUGS section.) .PP .\" 2012-05-05, According to Casper Dik, the statement about .\" Solaris was not true at least as far back as 1997, and .\" may never have been true. .\" .\" The 4.4BSD, Linux and SUSv2 versions always return an absolute .\" pathname. .\" Solaris may return a relative pathname when the .\" .I path .\" argument is relative. .\" The prototype of .\" .BR realpath () .\" is given in \fI\fP in libc4 and libc5, .\" but in \fI\fP everywhere else. .SS GNU extensions If the call fails with either .BR EACCES or .BR ENOENT and .I resolved_path is not NULL, then the prefix of .I path that is not readable or does not exist is returned in .IR resolved_path . .SH BUGS The POSIX.1-2001 standard version of this function is broken by design, since it is impossible to determine a suitable size for the output buffer, .IR resolved_path . According to POSIX.1-2001 a buffer of size .B PATH_MAX suffices, but .B PATH_MAX need not be a defined constant, and may have to be obtained using .BR pathconf (3). And asking .BR pathconf (3) does not really help, since, on the one hand POSIX warns that the result of .BR pathconf (3) may be huge and unsuitable for mallocing memory, and on the other hand .BR pathconf (3) may return \-1 to signify that .B PATH_MAX is not bounded. The .I "resolved_path\ ==\ NULL" feature, not standardized in POSIX.1-2001, but standardized in POSIX.1-2008, allows this design problem to be avoided. .\" .LP .\" The libc4 and libc5 implementation contained a buffer overflow .\" (fixed in libc-5.4.13). .\" Thus, set-user-ID programs like .\" .BR mount (8) .\" needed a private version. .SH SEE ALSO .BR realpath (1), .BR readlink (2), .BR canonicalize_file_name (3), .BR getcwd (3), .BR pathconf (3), .BR sysconf (3) .SH COLOPHON This page is part of release 4.16 of the Linux .I man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at \%https://www.kernel.org/doc/man\-pages/.