NAME
pathconf,
fpathconf —
get configurable pathname
variables
LIBRARY
library “libc”
SYNOPSIS
#include
<unistd.h>
long
pathconf(const
char *path, int
name);
long
fpathconf(int
fd, int name);
DESCRIPTION
Thepathconf()
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 ofmaxsize. _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
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.