NAME

fpathconf, pathconf - get configurable pathname variables

 SYNOPSIS

#include <unistd.h>

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

 DESCRIPTION

The fpathconf() and pathconf() functions provide a method for the application to determine the current value of a configurable limit or option (variable) that is associated with a file or directory.

For pathconf(), the path argument points to the pathname of a file or directory.

For fpathconf(), the fildes argument is an open file descriptor.

The name argument represents the variable to be queried relative to that file or directory. Implementations will support all of the variables listed in the following table and may support others. The variables in the following table come from <limits.h> or <unistd.h> and the symbolic constants, defined in <unistd.h>, are the corresponding values used for name:

Variable	Value of name	Notes
FILESIZEBITS	_PC_FILESIZEBITS	3,4
LINK_MAX	_PC_LINK_MAX	1
MAX_CANON	_PC_MAX_CANON	2
MAX_INPUT	_PC_MAX_INPUT	2
NAME_MAX	_PC_NAME_MAX	3,4
PATH_MAX	_PC_PATH_MAX	4,5
PIPE_BUF	_PC_PIPE_BUF	6
_POSIX_CHOWN_RESTRICTED	_PC_CHOWN_RESTRICTED	7
_POSIX_NO_TRUNC	_PC_NO_TRUNC	3,4
_POSIX_VDISABLE	_PC_VDISABLE	2
_POSIX_ASYNC_IO	_PC_ASYNC_IO	8
_POSIX_PRIO_IO	_PC_PRIO_IO	8
_POSIX_SYNC_IO	_PC_SYNC_IO	8

Notes:

1. If path or fildes refers to a directory, the value returned applies to the directory itself.

2. If path or fildes does not refer to a terminal file, it is unspecified whether an implementation supports an association of the variable name with the specified file.

3. If path or fildes refers to a directory, the value returned applies to filenames within the directory.

4. If path or fildes does not refer to a directory, it is unspecified whether an implementation supports an association of the variable name with the specified file.

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 refers to a FIFO, or fildes refers to a pipe or FIFO, the value returned applies to the referenced object. If path or fildes refers to a directory, the value returned applies to any FIFO that exists or can be created within the directory. If path or fildes refers to any other type of file, it is unspecified whether an implementation supports an association of the variable name with the specified file.

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.

8. If path or fildes refers to a directory, it is unspecified whether an implementation supports an association of the variable name with the specified file.

 RETURN VALUE

If name is an invalid value, both pathconf() and fpathconf() return -1 and errno is set to indicate the error.

If the variable corresponding to name has no limit for the path or file descriptor, both pathconf() and fpathconf() return -1 without changing errno. If the implementation needs to use path to determine the value of name and the implementation does not support the association of name with the file specified by path, or if the process did not have appropriate privileges to query the file specified by path, or path does not exist, pathconf() returns -1 and errno is set to indicate the error.

If the implementation needs to use fildes to determine the value of name and the implementation does not support the association of name with the file specified by fildes, or if fildes is an invalid file descriptor, fpathconf() will return -1 and errno is set to indicate the error.

Otherwise pathconf() or fpathconf() returns the current variable value for the file or directory without changing errno. The value returned will not be more restrictive than the corresponding value available to the application when it was compiled with the implementation's <limits.h> or <unistd.h>.

 ERRORS

The pathconf() function will fail if:

[EINVAL]

The value of name is not valid.

[ELOOP]

Too many symbolic links were encountered in resolving path.

The pathconf() function may fail if:

[EACCES]

Search permission is denied for a component of the path prefix.

[EINVAL]

The implementation does not support an association of the variable name with the specified file.

[ENAMETOOLONG]

The length of the path argument exceeds {PATH_MAX} or a pathname component is longer than {NAME_MAX}.

[ENAMETOOLONG]

Pathname resolution of a symbolic link produced an intermediate result whose length exceeds {PATH_MAX}.

[ENOENT]

A component of path does not name an existing file or path is an empty string.

[ENOTDIR]

A component of the path prefix is not a directory.

The fpathconf() function will fail if:

[EINVAL]

The value of name is not valid.

The fpathconf() function may fail if:

[EBADF]

The fildes argument is not a valid file descriptor.

[EINVAL]

The implementation does not support an association of the variable name with the specified file.

 EXAMPLES

None.

 APPLICATION USAGE

None.

 FUTURE DIRECTIONS

None.

 SEE ALSO

confstr(), sysconf(), <limits.h>, <unistd.h>, the XCU specification of getconf.

DERIVATION

Derived from the POSIX.1-1988 standard.