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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).

       ┌────────────────────────┬───────────────┬─────────┐
       │InterfaceAttributeValue   │
       ├────────────────────────┼───────────────┼─────────┤
       │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

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