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  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 FI-
              FOs 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  ap-
              plies 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  re-
          turned.)

       *  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  re-
              solving 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 at-
       tributes(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
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       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)