pathconf(2)

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() system calls provide a method

for applications to determine the current value of a configurable sys

tem limit or
option variable associated with a pathname or file descrip

tor.

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. Sym

bolic 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 privilege is required for

the chown(2)
system call, otherwise 0. requires appropriate

privilege in all
cases, but this behavior was optional in prior edi

tions of the
standard.

_PC_NO_TRUNC

Return greater than zero if attempts to use pathname

components
longer than {NAME_MAX} will result in an [ENAMETOO

LONG] error;
otherwise, such components will be truncated to

{NAME_MAX}.
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 be

tween
_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_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.

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 corre

sponding value.

[EINVAL] The value of the name argument is in

valid.

[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} charac

ters (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 compo

nent of the

path prefix.

[ELOOP] Too many symbolic links were encountered

in translat

ing the pathname.

[EIO] An I/O error occurred while reading from

or writing to

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.

SEE ALSO

sysctl(3)

HISTORY

The pathconf() and fpathconf() system calls first appeared

in 4.4BSD.

BSD November 4, 2002

BSD