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realpath (3)
  • realpath (1) ( FreeBSD man: Команды и прикладные программы пользовательского уровня )
  • realpath (3) ( Solaris man: Библиотечные вызовы )
  • realpath (3) ( FreeBSD man: Библиотечные вызовы )
  • realpath (3) ( Русские man: Библиотечные вызовы )
  • >> realpath (3) ( Linux man: Библиотечные вызовы )
  • realpath (3) ( POSIX man: Библиотечные вызовы )
  •  

    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  

    DESCRIPTION

    realpath() expands all symbolic links and resolves references to /./, /../ and extra aq/aq 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 butes, 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. The global variable 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 says that the behavior if resolved_path is NULL is implementation-defined. POSIX.1-2008 specifies the behavior described in this page. 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

    Avoid using this function. It is broken by design since (unless using the non-standard resolved_path == NULL feature) it is impossible to determine a suitable size for the output buffer, resolved_path. According to POSIX 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 libc4 and libc5 implementation contains a buffer overflow (fixed in libc-5.4.13). Thus, set-user-ID programs like mount(8) need a private version.  

    SEE ALSO

    readlink(2), canonicalize_file_name(3), getcwd(3), pathconf(3), sysconf(3)  

    COLOPHON

    This page is part of release 3.14 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/.


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUE
    ERRORS
    VERSIONS
    CONFORMING TO
    BUGS
    SEE ALSO
    COLOPHON


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