NAME

pathconf, fpathconf — get configurable pathname variables

LIBRARY

Standard C Library (libc, -lc)

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 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]

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 IEEE Std 1003.1-1990 (“POSIX.1”).

HISTORY

The pathconf and fpathconf functions first appeared in 4.4BSD.