NAME

     pathconf, lpathconf, fpathconf — get configurable pathname variables

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <unistd.h>

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

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

     long
     fpathconf(int fd, int name);

DESCRIPTION

     The pathconf(), lpathconf() and fpathconf() system calls provide a method for applications
     to determine the current value of a configurable system limit or option variable associated
     with a pathname or file descriptor.

     For pathconf() and lpathconf(), 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 lpathconf() system call is like pathconf() except in the case where the named file is a
     symbolic link, in which case lpathconf() returns information about the link, while
     pathconf() returns information about the file the link references.

     The available values are as follows:

     _PC_LINK_MAX
             The maximum file link count.

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

     _PC_MAX_INPUT
             The minimum 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
             Return 1 if appropriate privilege is 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
             Return greater than zero 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 behavior.

     _PC_VDISABLE
             Returns the terminal character disabling value.

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

     _PC_PRIO_IO
             Returns 1 if prioritised I/O is supported for this file, otherwise 0.

     _PC_SYNC_IO
             Returns 1 if synchronised I/O is supported for this file, otherwise 0.

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

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

     _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_ACL_EXTENDED
             Returns 1 if an Access Control List (ACL) can be set on the specified file,
             otherwise 0.

     _PC_ACL_NFS4
             Returns 1 if an NFSv4 ACLs can be set on the specified file, otherwise 0.

     _PC_ACL_PATH_MAX
             Maximum number of ACL entries per file.

     _PC_CAP_PRESENT
             Returns 1 if a capability state can be set on the specified file, otherwise 0.

     _PC_INF_PRESENT
             Returns 1 if an information label can be set on the specified file, otherwise 0.

     _PC_MAC_PRESENT
             Returns 1 if a Mandatory Access Control (MAC) label can be set on the specified
             file, otherwise 0.

     _PC_MIN_HOLE_SIZE
             If a file system supports the reporting of holes (see lseek(2)), pathconf() and
             fpathconf() return a positive number that represents the minimum hole size returned
             in bytes.  The offsets of holes returned will be aligned to this same value.  A
             special value of 1 is returned if the file system does not specify the minimum hole
             size but still reports holes.

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() system calls 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.

     The pathconf() system call 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 path name exceeded {PATH_MAX}
                        characters.

     [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 translating the pathname.

     [EIO]              An I/O error occurred while reading from or writing to the file system.

     [EINTEGRITY]       Corrupted data was detected while reading from the file system.

     The fpathconf() system call will fail if:

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

     [EIO]              An I/O error occurred while reading from or writing to the file system.

     [EINTEGRITY]       Corrupted data was detected while reading from the file system.

SEE ALSO

     lseek(2), sysctl(3)

HISTORY

     The pathconf() and fpathconf() system calls first appeared in 4.4BSD.  The lpathconf()
     system call first appeared in FreeBSD 8.0.