pathconf

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



NAME
       fpathconf, pathconf - get configuration values for files

SYNOPSIS
       #include <unistd.h>

       long fpathconf(int fd, int name);
       long pathconf(const char *path, int name);

DESCRIPTION
       fpathconf() gets a value for the configuration option name for the open
       file descriptor fd.

       pathconf() gets a value for configuration option name for the filename
       path.

       The corresponding macros defined in <unistd.h> are minimum values; if an
       application wants to take advantage of values which may change, a call to
       fpathconf() or pathconf() can be made, which may yield more liberal
       results.

       Setting name equal to one of the following constants returns the
       following configuration options:

       _PC_LINK_MAX
              The maximum number of links to the file.  If fd or path refer to a
              directory, then the value applies to the whole directory.  The
              corresponding macro is _POSIX_LINK_MAX.

       _PC_MAX_CANON
              The maximum length of a formatted input line, where fd or path
              must refer to a terminal.  The corresponding macro is
              _POSIX_MAX_CANON.

       _PC_MAX_INPUT
              The maximum length of an input line, where fd or path must refer
              to a terminal.  The corresponding macro is _POSIX_MAX_INPUT.

       _PC_NAME_MAX
              The maximum length of a filename in the directory path or fd that
              the process is allowed to create.  The corresponding macro is
              _POSIX_NAME_MAX.

       _PC_PATH_MAX
              The maximum length of a relative pathname when path or fd is the
              current working directory.  The corresponding macro is
              _POSIX_PATH_MAX.

       _PC_PIPE_BUF
              The maximum number of bytes that can be written atomically to a
              pipe of FIFO.  For fpathconf(), fd should refer to a pipe or FIFO.
              For fpathconf(), path should refer to a FIFO or a directory; in
              the latter case, the returned value corresponds to FIFOs created
              in that directory.  The corresponding macro is _POSIX_PIPE_BUF.

       _PC_CHOWN_RESTRICTED
              This returns a positive value if the use of chown(2) and fchown(2)
              for changing a file's user ID is restricted to a process with
              appropriate privileges, and changing a file's group ID to a value
              other than the process's effective group ID or one of its
              supplementary group IDs is restricted to a process with
              appropriate privileges.  According to POSIX.1, this variable shall
              always be defined with a value other than -1.  The corresponding
              macro is _POSIX_CHOWN_RESTRICTED.

              If fd or path refers to a directory, then the return value applies
              to all files in that directory.

       _PC_NO_TRUNC
              This returns nonzero if accessing filenames longer than
              _POSIX_NAME_MAX generates an error.  The corresponding macro is
              _POSIX_NO_TRUNC.

       _PC_VDISABLE
              This returns nonzero if special character processing can be
              disabled, where fd or path must refer to a terminal.

RETURN VALUE
       The return value of these functions is one of the following:

       *  On error, -1 is returned and errno is set to indicate the cause of the
          error (for example, EINVAL, indicating that name is invalid).

       *  If name corresponds to a maximum or minimum limit, and that limit is
          indeterminate, -1 is returned and errno is not changed.  (To
          distinguish an indeterminate limit from an error, set errno to zero
          before the call, and then check whether errno is nonzero when -1 is
          returned.)

       *  If name corresponds to an option, a positive value is returned if the
          option is supported, and -1 is returned if the option is not
          supported.

       *  Otherwise, the current value of the option or limit is returned.  This
          value will not be more restrictive than the corresponding value that
          was described to the application in <unistd.h> or <limits.h> when the
          application was compiled.

ERRORS
       EACCES (pathconf()) Search permission is denied for one of the
              directories in the path prefix of path.

       EBADF  (fpathconf()) fd is not a valid file descriptor.

       EINVAL name is invalid.

       EINVAL The implementation does not support an association of name with
              the specified file.

       ELOOP  (pathconf()) Too many symbolic links were encountered while
              resolving path.

       ENAMETOOLONG
              (pathconf()) path is too long.

       ENOENT (pathconf()) A component of path does not exist, or path is an
              empty string.

       ENOTDIR
              (pathconf()) A component used as a directory in path is not in
              fact a directory.

ATTRIBUTES
       For an explanation of the terms used in this section, see attributes(7).

       ┌────────────────────────┬───────────────┬─────────┐
       │Interface               Attribute     Value   │
       ├────────────────────────┼───────────────┼─────────┤
       │fpathconf(), pathconf() │ Thread safety │ MT-Safe │
       └────────────────────────┴───────────────┴─────────┘
CONFORMING TO
       POSIX.1-2001, POSIX.1-2008.

NOTES
       Files with name lengths longer than the value returned for name equal to
       _PC_NAME_MAX may exist in the given directory.

       Some returned values may be huge; they are not suitable for allocating
       memory.

SEE ALSO
       getconf(1), open(2), statfs(2), confstr(3), sysconf(3)

COLOPHON
       This page is part of release 5.09 of the Linux 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/.




GNU                                2017-07-13                       FPATHCONF(3)