realpath(3) [netbsd man page]
REALPATH(3) BSD Library Functions Manual REALPATH(3) NAME
realpath -- returns the canonicalized absolute pathname LIBRARY
Standard C Library (libc, -lc) SYNOPSIS
#include <sys/param.h> #include <stdlib.h> char * realpath(const char * restrict pathname, char * restrict resolvedname); DESCRIPTION
The realpath() function resolves all symbolic links, extra ``/'' characters and references to /./ and /../ in pathname, and copies the resulting absolute pathname into the memory referenced by resolvedname. The resolvedname argument must refer to a buffer capable of storing at least MAXPATHLEN characters. The realpath() function will resolve both absolute and relative paths and return the absolute pathname corresponding to pathname. RETURN VALUES
If resolvednamed is NULL, it will be allocated and the returned pointer can be deallocated using free(3). The realpath() function returns resolvedname on success. If an error occurs, realpath() returns NULL, and resolvedname was not allocated by realpath, it will contain the pathname which caused the problem. ERRORS
The function realpath() may fail and set the external variable errno for any of the errors specified for the library functions chdir(2), close(2), fchdir(2), lstat(2), malloc(3), open(2), readlink(2) and getcwd(3). SEE ALSO
getcwd(3) STANDARDS
realpath() first appeared in X/Open Portability Guide Issue 4, Version 2 (``XPG4.2'') and is part of IEEE Std 1003.1-2001 (``POSIX.1''). HISTORY
The realpath() function call first appeared in 4.4BSD. In NetBSD 7.0 the function was updated to accept a NULL pointer for the resolvedname argument. BUGS
This implementation of realpath() differs slightly from the Solaris implementation. The 4.4BSD version always returns absolute pathnames, whereas the Solaris implementation will, under certain circumstances, return a relative resolvedname when given a relative pathname. BSD
June 21, 2012 BSD
Check Out this Related Man Page
REALPATH(3) Linux Programmer's Manual REALPATH(3) NAME
realpath - return the canonicalized absolute pathname SYNOPSIS
#include <limits.h> #include <stdlib.h> char *realpath(const char *path, char *resolved_path); Feature Test Macro Requirements for glibc (see feature_test_macros(7)): realpath(): _BSD_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED DESCRIPTION
realpath() expands all symbolic links and resolves references to /./, /../ and extra '/' characters in the null-terminated string named by path to produce a canonicalized absolute pathname. The resulting pathname is stored as a null-terminated string, up to a maximum of PATH_MAX bytes, in the buffer pointed to by resolved_path. The resulting path will have no symbolic link, /./ or /../ components. If resolved_path is specified as NULL, then realpath() uses malloc(3) to allocate a buffer of up to PATH_MAX bytes to hold the resolved pathname, and returns a pointer to this buffer. The caller should deallocate this buffer using free(3). RETURN VALUE
If there is no error, realpath() returns a pointer to the resolved_path. Otherwise it returns a NULL pointer, and the contents of the array resolved_path are undefined, and errno is set to indicate the error. ERRORS
EACCES Read or search permission was denied for a component of the path prefix. EINVAL Either path or resolved_path is NULL. (In libc5 this would just cause a segfault.) But, see NOTES below. EIO An I/O error occurred while reading from the file system. ELOOP Too many symbolic links were encountered in translating the pathname. ENAMETOOLONG A component of a pathname exceeded NAME_MAX characters, or an entire pathname exceeded PATH_MAX characters. ENOENT The named file does not exist. ENOTDIR A component of the path prefix is not a directory. VERSIONS
On Linux this function appeared in libc 4.5.21. CONFORMING TO
4.4BSD, POSIX.1-2001. POSIX.1-2001 says that the behavior if resolved_path is NULL is implementation-defined. POSIX.1-2008 specifies the behavior described in this page. NOTES
In 4.4BSD and Solaris the limit on the pathname length is MAXPATHLEN (found in <sys/param.h>). SUSv2 prescribes PATH_MAX and NAME_MAX, as found in <limits.h> or provided by the pathconf(3) function. A typical source fragment would be #ifdef PATH_MAX path_max = PATH_MAX; #else path_max = pathconf(path, _PC_PATH_MAX); if (path_max <= 0) path_max = 4096; #endif (But see the BUGS section.) The 4.4BSD, Linux and SUSv2 versions always return an absolute pathname. Solaris may return a relative pathname when the path argument is relative. The prototype of realpath() is given in <unistd.h> in libc4 and libc5, but in <stdlib.h> everywhere else. 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, resolved_path. According to POSIX.1-2001 a buffer of size PATH_MAX suffices, but PATH_MAX need not be a defined constant, and may have to be obtained using pathconf(3). And asking pathconf(3) does not really help, since, on the one hand POSIX warns that the result of pathconf(3) may be huge and unsuitable for mallocing memory, and on the other hand pathconf(3) may return -1 to signify that PATH_MAX is not bounded. The resolved_path == NULL feature, not standardized in POSIX.1-2001, but standardized in POSIX.1-2008, allows this design problem to be avoided. The libc4 and libc5 implementation contains a buffer overflow (fixed in libc-5.4.13). Thus, set-user-ID programs like mount(8) need a pri- vate version. SEE ALSO
readlink(2), canonicalize_file_name(3), getcwd(3), pathconf(3), sysconf(3) COLOPHON
This page is part of release 3.27 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. 2010-09-20 REALPATH(3)