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PATHCONF(2)                 BSD System Calls Manual                PATHCONF(2)

NAME
     pathconf, fpathconf -- get configurable pathname variables

SYNOPSIS
     #include <&lt;unistd.h>&gt;

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

     long
     fpathconf(int fd, int name);

DESCRIPTION
     The pathconf() and fpathconf() functions provide a method for applica-
     tions to determine the current value of a configurable system limit or
     option variable associated with a pathname or file descriptor.

     For pathconf, the path argument is the name of a file or directory.  For
     fpathconf, the fd argument is an open file descriptor.  The name argument
     specifies the system variable to be queried.  Symbolic constants for each
     name value are found in the include file <unistd.h>.

     The available values are as follows:

     _PC_LINK_MAX
             The maximum file link count.

     _PC_MAX_CANON
             The maximum number of bytes in a terminal canonical input line.

     _PC_MAX_INPUT
             The maximum number of bytes for which space is available in a
             terminal input queue.

     _PC_NAME_MAX
             The maximum number of bytes in a file name.

     _PC_PATH_MAX
             The maximum number of bytes in a pathname.

     _PC_PIPE_BUF
             The maximum number of bytes which will be written atomically to a
             pipe.

     _PC_CHOWN_RESTRICTED
             Returns 1 if appropriate privileges are required for the chown(2)
             system call, otherwise 0.  IEEE Std 1003.1-2001 (``POSIX.1'')
             requires appropriate privilege in all cases, but this behavior
             was optional in prior editions of the standard.

     _PC_NO_TRUNC
             Returns 1 if attempts to use pathname components longer than
             {NAME_MAX} will result in an [ENAMETOOLONG] error; otherwise,
             such components will be truncated to {NAME_MAX}.  IEEE Std
             1003.1-2001 (``POSIX.1'') requires the error in all cases, but
             this behavior was optional in prior editions of the standard, and
             some non-POSIX-compliant file systems do not support this behav-
             ior.

     _PC_VDISABLE
             Returns the terminal character disabling value.

     _PC_2_SYMLINKS
             Returns 1 if the filesystem supports the creation of symbolic
             links within the specified directory; the meaning of
             _PC_2_SYMLINKS is unspecified for non-directory files.

     _PC_ALLOC_SIZE_MIN
             Minimum number of bytes of storage allocated for any portion of a
             file.

     _PC_ASYNC_IO
             Returns 1 if asynchronous I/O is supported, otherwise 0.

     _PC_FILESIZEBITS
             Number of bits needed to represent the maximum file size.

     _PC_PRIO_IO
             Returns 1 if prioritized I/O is supported, otherwise 0.

     _PC_REC_INCR_XFER_SIZE
             Recommended increment for file transfer sizes between
             _PC_REC_MIN_XFER_SIZE and _PC_REC_MAX_XFER_SIZE.

     _PC_REC_MAX_XFER_SIZE
             Maximum recommended file transfer size.

     _PC_REC_MIN_XFER_SIZE
             Minimum recommended file transfer size.

     _PC_REC_XFER_ALIGN
             Recommended file transfer buffer alignment.

     _PC_SYMLINK_MAX
             Maximum number of bytes in a symbolic link.

     _PC_SYNC_IO
             Returns 1 if synchronized I/O is supported, otherwise 0.

     _PC_TIMESTAMP_RESOLUTION
             The resolution in nanoseconds of file timestamps.

RETURN VALUES
     If the call to pathconf or fpathconf is not successful, -1 is returned
     and errno is set appropriately.  Otherwise, if the variable is associated
     with functionality that does not have a limit in the system, -1 is
     returned and errno is not modified.  Otherwise, the current variable
     value is returned.

ERRORS
     If any of the following conditions occur, the pathconf and fpathconf
     functions shall return -1 and set errno to the corresponding value.

     [EINVAL]           The value of the name argument is invalid.

     [EINVAL]           The implementation does not support an association of
                        the variable name with the associated file.

     [EIO]              An I/O error occurred while reading from the file sys-
                        tem.

     pathconf() will fail if:

     [ENOTDIR]          A component of the path prefix is not a directory.

     [ENAMETOOLONG]     A component of a pathname exceeded NAME_MAX characters
                        (but see _PC_NO_TRUNC above), or an entire pathname
                        (including the terminating NUL) exceeded PATH_MAX
                        bytes.

     [ENOENT]           The named file does not exist.

     [EACCES]           Search permission is denied for a component of the
                        path prefix.

     [ELOOP]            Too many symbolic links were encountered in translat-
                        ing the pathname.

     [EFAULT]           path points outside the process's allocated address
                        space.

     fpathconf() will fail if:

     [EBADF]            fd is not a valid open file descriptor.

SEE ALSO
     sysconf(3), sysctl(3)

STANDARDS
     The pathconf and fpathconf functions conform to IEEE Std 1003.1-2008
     (``POSIX.1'').

HISTORY
     The pathconf and fpathconf functions first appeared in 4.4BSD.

BSD                             March 28, 2017                             BSD