FPATHCONF(3) Linux Programmer's Manual FPATHCONF(3)
NAME
fpathconf, pathconf - get configuration values for files
SYNOPSIS
#include <unistd.h>
long fpathconf(int fd, int name);
long pathconf(const char *path, int name);
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 fol-
lowing 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 direc-
tory; 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 corre-
sponding 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 dis-
abled, where fd or path must refer to a terminal.
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 cause of
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 distin-
guish 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.
ERRORS
EACCES (pathconf()) Search permission is denied for one of the directo-
ries 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.
ATTRIBUTES
For an explanation of the terms used in this section, see
attributes(7).
+------------------------+---------------+---------+
|Interface | Attribute | Value |
+------------------------+---------------+---------+
|fpathconf(), pathconf() | Thread safety | MT-Safe |
+------------------------+---------------+---------+
CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
NOTES
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.
SEE ALSO
getconf(1), open(2), statfs(2), confstr(3), sysconf(3)
COLOPHON
This page is part of release 4.15 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/.
GNU 2017-07-13 FPATHCONF(3)
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