fpathconf, pathconf — get configuration values for files
#include <unistd.h>
long
fpathconf( |
int fd, |
int name); |
long
pathconf( |
const char *path, |
int name); |
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_MAXThe 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_CANONThe 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_INPUTThe maximum length of an input line, where
fd or
path must refer
to a terminal. The corresponding macro is _POSIX_MAX_INPUT.
_PC_NAME_MAXThe 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_MAXThe maximum length of a relative pathname when
path or
fd is the
current working directory. The corresponding macro is
_POSIX_PATH_MAX.
_PC_PIPE_BUFThe 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_RESTRICTEDThis 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_TRUNCThis returns nonzero if accessing filenames longer
than _POSIX_NAME_MAX
generates an error. The corresponding macro is
_POSIX_NO_TRUNC.
_PC_VDISABLEThis returns nonzero if special character processing
can be disabled, where fd or path must refer to a
terminal.
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.
(pathconf()) Search
permission is denied for one of the directories in the
path prefix of path.
(fpathconf())
fd is not a
valid file descriptor.
name is
invalid.
The implementation does not support an association
of name with
the specified file.
(pathconf()) Too many
symbolic links were encountered while resolving
path.
(pathconf())
path is too
long.
(pathconf()) A
component of path does not exist, or
path is an
empty string.
(pathconf()) A
component used as a directory in path is not in fact a
directory.
For an explanation of the terms used in this section, see attributes(7).
| Interface | Attribute | Value |
fpathconf(), pathconf() |
Thread safety | MT-Safe |
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.
This page is part of release 5.11 of the Linux man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
https://www.kernel.org/doc/man−pages/.
|
Copyright (c) 1993 by Thomas Koenig (ig25rz.uni-karlsruhe.de) and Copyright (C) 2017 Michael Kerrisk <mtk.manpagesgmail.com> %%%LICENSE_START(VERBATIM) Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Since the Linux kernel and libraries are constantly changing, this manual page may be incorrect or out-of-date. The author(s) assume no responsibility for errors or omissions, or for damages resulting from the use of the information contained herein. The author(s) may not have taken the same level of care in the production of this manual, which is licensed free of charge, as they might when working professionally. Formatted or processed versions of this manual, if unaccompanied by the source, must acknowledge the copyright and authors of this work. %%%LICENSE_END Modified Wed Jul 28 11:12:26 1993 by Rik Faith (faithcs.unc.edu) FIXME Probably all of the following should be documented: _PC_SYNC_IO, _PC_ASYNC_IO, _PC_PRIO_IO, _PC_SOCK_MAXBUF, _PC_FILESIZEBITS, _PC_REC_INCR_XFER_SIZE, _PC_REC_MAX_XFER_SIZE, _PC_REC_MIN_XFER_SIZE, _PC_REC_XFER_ALIGN, _PC_ALLOC_SIZE_MIN, _PC_SYMLINK_MAX, _PC_2_SYMLINKS |