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canonicalize_file_name(3) [centos man page]

CANONICALIZE_FILE_NAME(3)				     Linux Programmer's Manual					 CANONICALIZE_FILE_NAME(3)

canonicalize_file_name - return the canonicalized absolute pathname SYNOPSIS
#define _GNU_SOURCE /* See feature_test_macros(7) */ #include <stdlib.h> char *canonicalize_file_name(const char *path); DESCRIPTION
The canonicalize_file_name() function returns a null-terminated string containing the canonicalized absolute pathname corresponding to path. In the returned string, symbolic links are resolved, as are . and .. pathname components. Consecutive slash (/) characters are replaced by a single slash. The returned string is dynamically allocated by canonicalize_file_name() and the caller should deallocate it with free(3) when it is no longer required. The call canonicalize_file_name(path) is equivalent to the call: realpath(path, NULL); RETURN VALUE
On success, canonicalize_file_name() returns a null-terminated string. On error (e.g., a pathname component is unreadable or does not exist), canonicalize_file_name() returns NULL and sets errno to indicate the error. ERRORS
See realpath(3). CONFORMING TO
This function is a GNU extension. SEE ALSO
readlink(2), realpath(3) COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at GNU

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REALPATH(3)						     Linux Programmer's Manual						       REALPATH(3)

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 2010-09-20 REALPATH(3)
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