PATHCONF(2)

NAME
pathconf, fpathconf - get configurable pathname variables

LIBRARY
libc

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

DESCRIPTION
The pathconf() and fpathconf() functions 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, 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 <unistd.h> header.

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 filename, not including a terminating null character.

_PC_PATH_MAX
    The maximum number of bytes in a pathname, including the terminating null character.

_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 0 if filenames longer than {NAME_MAX} are silently truncated, or non-zero if an error is generated when {NAME_MAX} is exceeded.

_PC_VDISABLE
    Returns the terminal character disabling value.

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

_PC_FILESIZEBITS
    If the maximum size file that could ever exist on the mounted file system is maxsize, then the returned value is 2 plus the floor of the base 2 logarithm of maxsize.

_PC_SYMLINK_MAX
    The maximum number of bytes in a symbolic link.

_PC_2_SYMLINKS
    When referring to a directory the system supports the creation of symbolic links within that directory; for nondirectory files, the meaning of {_PC_2_SYMLINKS} is undefined.

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, or 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 occurred while reading from or writing to the file system.

[ELOOP]
    Too many symbolic links were encountered in translating the pathname.

[ENAMETOOLONG]
    A component of a pathname exceeded {NAME_MAX} characters, or an entire path name exceeded {PATH_MAX} characters.

[ENOENT]
    The named file does not exist.

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

fpathconf() will fail if:

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

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

SEE ALSO
sysctl(3)

STANDARDS
The pathconf() and fpathconf() functions conform to p1003.1-90.

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