fpathconf, pathconf - get configuration values for files
Standard C library (
libc,
-lc)
#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_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.
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.
- 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.
For an explanation of the terms used in this section, see
attributes(7).
Interface |
Attribute |
Value |
fpathconf (), pathconf () |
Thread safety |
MT-Safe |
POSIX.1-2001, POSIX.1-2008.
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.
getconf(1),
open(2),
statfs(2),
confstr(3),
sysconf(3)