получить значения конфигурации для файлов (get configuration values for files)
Имя (Name)
fpathconf, pathconf - get configuration values for files
Синопсис (Synopsis)
#include <unistd.h>
long fpathconf(int fd, int name);
long pathconf(const char *path, int name);
Описание (Description)
fpathconf() gets a value for the configuration option name for
the open file descriptor fd.
pathconf() gets a value for configuration option name for the
filename path.
The corresponding macros defined in <unistd.h> are minimum
values; if an application wants to take advantage of values which
may change, a call to fpathconf() or pathconf() can be made,
which may yield more liberal results.
Setting name equal to one of the following constants returns the
following configuration options:
_PC_LINK_MAX
The maximum number of links to the file. If fd or path
refer to a directory, then the value applies to the whole
directory. The corresponding macro is _POSIX_LINK_MAX.
_PC_MAX_CANON
The maximum length of a formatted input line, where fd or
path must refer to a terminal. The corresponding macro is
_POSIX_MAX_CANON.
_PC_MAX_INPUT
The maximum length of an input line, where fd or path must
refer to a terminal. The corresponding macro is
_POSIX_MAX_INPUT.
_PC_NAME_MAX
The maximum length of a filename in the directory path or
fd that the process is allowed to create. The
corresponding macro is _POSIX_NAME_MAX.
_PC_PATH_MAX
The maximum length of a relative pathname when path or fd
is the current working directory. The corresponding macro
is _POSIX_PATH_MAX.
_PC_PIPE_BUF
The maximum number of bytes that can be written atomically
to a pipe of FIFO. For fpathconf(), fd should refer to a
pipe or FIFO. For fpathconf(), path should refer to a
FIFO or a directory; in the latter case, the returned
value corresponds to FIFOs created in that directory. The
corresponding macro is _POSIX_PIPE_BUF.
_PC_CHOWN_RESTRICTED
This returns a positive value if the use of chown(2) and
fchown(2) for changing a file's user ID is restricted to a
process with appropriate privileges, and changing a file's
group ID to a value other than the process's effective
group ID or one of its supplementary group IDs is
restricted to a process with appropriate privileges.
According to POSIX.1, this variable shall always be
defined with a value other than -1. The corresponding
macro is _POSIX_CHOWN_RESTRICTED.
If fd or path refers to a directory, then the return value
applies to all files in that directory.
_PC_NO_TRUNC
This returns nonzero if accessing filenames longer than
_POSIX_NAME_MAX generates an error. The corresponding
macro is _POSIX_NO_TRUNC.
_PC_VDISABLE
This returns nonzero if special character processing can
be disabled, where fd or path must refer to a terminal.
Возвращаемое значение (Return value)
The return value of these functions is one of the following:
* On error, -1 is returned and errno is set to indicate the
error (for example, EINVAL, indicating that name is invalid).
* If name corresponds to a maximum or minimum limit, and that
limit is indeterminate, -1 is returned and errno is not
changed. (To distinguish an indeterminate limit from an
error, set errno to zero before the call, and then check
whether errno is nonzero when -1 is returned.)
* If name corresponds to an option, a positive value is returned
if the option is supported, and -1 is returned if the option
is not supported.
* Otherwise, the current value of the option or limit is
returned. This value will not be more restrictive than the
corresponding value that was described to the application in
<unistd.h> or <limits.h> when the application was compiled.
Ошибки (Error)
EACCES (pathconf()) Search permission is denied for one of the
directories in the path prefix of path.
EBADF (fpathconf()) fd is not a valid file descriptor.
EINVAL name is invalid.
EINVAL The implementation does not support an association of name
with the specified file.
ELOOP (pathconf()) Too many symbolic links were encountered
while resolving path.
ENAMETOOLONG
(pathconf()) path is too long.
ENOENT (pathconf()) A component of path does not exist, or path
is an empty string.
ENOTDIR
(pathconf()) A component used as a directory in path is
not in fact a directory.
Атрибуты (Attributes)
For an explanation of the terms used in this section, see
attributes(7).
┌──────────────────────────────────────┬───────────────┬─────────┐
│Interface │ Attribute │ Value │
├──────────────────────────────────────┼───────────────┼─────────┤
│fpathconf(), pathconf() │ Thread safety │ MT-Safe │
└──────────────────────────────────────┴───────────────┴─────────┘
Стандарты (Conforming to)
POSIX.1-2001, POSIX.1-2008.
Примечание (Note)
Files with name lengths longer than the value returned for name
equal to _PC_NAME_MAX may exist in the given directory.
Some returned values may be huge; they are not suitable for
allocating memory.
Смотри также (See also)
getconf(1), open(2), statfs(2), confstr(3), sysconf(3)
