PATHCONF(2)

NAME
fpathconf, pathconf - get configurable pathname variables

SYNOPSIS
#include <unistd.h>
long
fpathconf(int fildes, int name);
long
pathconf(const char *path, int name);

DESCRIPTION

The pathconf() and fpathconf() functions provides 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, the path argument is the name of a file or directory. For fpathconf, the fildes 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 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 privileges are required for the chown(2) system call, otherwise 0.

_PC_NO_TRUNC
    Return 1 if file names longer than KERN_NAME_MAX are truncated.

_PC_VDISABLE
    Returns the terminal character disabling value.

_PC_XATTR_SIZE_BITS
    Returns the number of bits used to store maximum extended attribute size in bytes. For example, if the maximum attribute size supported by a file system is 128K, the value returned will be 18. However a value 18 can mean that the maximum attribute size can be anywhere from (256KB - 1) to 128KB. As a special case, the resource fork can have much larger size, and some file system specific extended attributes can have smaller and preset size; for example, Finder Info is always 32 bytes.

_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 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.

pathconf() will fail if:

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

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

[ELOOP]
    Too many symbolic links are encountered in translating the pathname. This is taken to be indicative of a looping symbolic link.

[ENAMETOOLONG]
    A component of a pathname exceeded 255 characters, or an entire path name exceeded 1023 characters.

[ENOENT]
    The named file does not exist.

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

fpathconf() will fail if:

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

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

SEE ALSO
sysctl(3)

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