GENWiki

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  fol-
     lowing 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  direc-
            tory;  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 corre-
            sponding 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 dis-
            abled, 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 distin-

        guish 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 directo-
            ries 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.