NAME
pathconf,
lpathconf, fpathconf
— get configurable pathname
variables
LIBRARY
library “libc”
SYNOPSIS
#include
<unistd.h>
long
pathconf(const
char *path, int
name);
long
lpathconf(const
char *path, int
name);
long
fpathconf(int
fd, int name);
DESCRIPTION
Thepathconf(),
lpathconf() and fpathconf()
system calls 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()
and lpathconf(), 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 include file
<unistd.h>.
The
lpathconf()
system call is like pathconf() except in the case
where the named file is a symbolic link, in which case
lpathconf() returns information about the link,
while pathconf() returns information about the file
the link references.
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. IEEE Std 1003.1-2001 (“POSIX.1”) requires appropriate privilege in all cases, but this behavior was optional in prior editions of the standard.
_PC_NO_TRUNC- Return greater than zero if attempts to use pathname components longer
than {
NAME_MAX} will result in an [ENAMETOOLONG] error; otherwise, such components will be truncated to {NAME_MAX}. IEEE Std 1003.1-2001 (“POSIX.1”) 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 between
_PC_REC_MIN_XFER_SIZEand_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_NFS4- Returns 1 if an NFSv4 ACLs 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.
_PC_MIN_HOLE_SIZE- If a file system supports the reporting of holes (see
lseek(2)),
pathconf() andfpathconf() 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()
system calls 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.
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} characters (but see_PC_NO_TRUNCabove), or an entire path name exceeded {PATH_MAX} characters. - [
ENOENT] - The named file does not exist.
- [
EACCES] - Search permission is denied for a component of the path prefix.
- [
ELOOP] - Too many symbolic links were encountered in translating 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
HISTORY
The pathconf() and
fpathconf() system calls first appeared in
4.4BSD. The lpathconf()
system call first appeared in FreeBSD 8.0.