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Name

fpathconf, pathconf - get configurable pathname variables

Synopsis

#include <unistd.h>

long fpathconf(int fildes, int name);

long pathconf(const char *path, int name);

MT-Level

pathconf() is Async-Signal-Safe

Description

The functions fpathconf() and pathconf() return the current value of a configurable limit or option associated with a file or directory. The path argument points to the pathname of a file or directory; fildes is an open file descriptor; and name is the symbolic constant (defined in <unistd.h>) representing the configurable system limit or option to be returned.

The values returned by pathconf() and fpathconf() depend on the type of file specified by path or fildes. The following table contains the symbolic constants supported by pathconf() and fpathconf() along with the POSIX defined return value. The return value is based on the type of file specified by path or fildes. 


Value of name    See Note
_PC_LINK_MAX    1
_PC_MAX_CANNON    2
_PC_MAX_INPUT    2
_PC_NAME_MAX    3,4
_PC_PATH_MAX    4,5
_PC_PIPE_BUF    6
_PC_CHOWN_RESTRICTED    7
_PC_NO_TRUNC    3,4
_PC_VDISABLE    2
_PC_ASYNC_IO    2
_PC_PRIO_IO    2
_PC_SYNC_IO    1

Notes:

1
If path or fildes refers to a directory, the value returned applies to the directory itself.
2
The behavior is undefined if path or fildes does not refer to a terminal file.
3
If path or fildes refers to a directory, the value returned applies to the filenames within the directory.
4
The behavior is undefined if path or fildes does not refer to a directory.
5
If path or fildes refers to a directory, the value returned is the maximum length of a relative pathname when the specified directory is the working directory.
6
If path or fildes refers to a pipe or FIFO, the value returned applies to the pipe or FIFO. If path or fildes refers to a directory, the value returned applies to any FIFOs that exist or can be created within the directory. If path or fildes refer to any other type of file, the behavior is undefined.
7
If path or fildes refers to a directory, the value returned applies to any files, other than directories, that exist or can be created within the directory.

The value of the configurable system limit or option specified by name does not change during the lifetime of the calling process.

Return Values

If fpathconf or pathconf are invoked with an invalid symbolic constant or the symbolic constant corresponds to a configurable system limit or option not supported on the system, a value of -1 is returned to the invoking process. If the function fails because the configurable system limit or option corresponding to name is not supported on the system the value of errno is not changed.

Errors

fpathconf() fails if the following is true:

EBADF
fildes is not a valid file descriptor.

pathconf() fails if one or more of the following are true:

EACCES
search permission is denied for a component of the path prefix.
ELOOP
too many symbolic links are encountered while translating path.
EMULTIHOP
components of path require hopping to multiple remote machines and file system type does not allow it.
ENAMETOOLONG
the length of a pathname exceeds {PATH_MAX}, or a pathname component is longer than {NAME_MAX} while {_POSIX_NO_TRUNC} is in effect.
ENOENT
path is needed for the command specified and the named file does not exist or if the path argument points to an empty string.
ENOLINK
path points to a remote machine and the link to that machine is no longer active.
ENOTDIR
a component of the path prefix is not a directory.

Both fpathconf() and pathconf() fail if the following is true:

EINVAL
if name is an invalid value.

See Also

sysconf(3C) , limits(4)

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