fpathconf, pathconf - get configuration values for files
long fpathconf(int fd, int name);
long pathconf(const char *path, int name);
() gets a value for the configuration option name
open file descriptor fd
() gets a value for configuration option name
The corresponding macros defined in <unistd.h>
are minimum values;
if an application wants to take advantage of values which may change, a call
() or pathconf
() can be made, which may yield more
equal to one of the following constants returns the
following configuration options:
- 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.
- The maximum length of a formatted input line, where
fd or path must refer to a terminal. The corresponding macro
- The maximum length of an input line, where fd or
path must refer to a terminal. The corresponding macro is
- 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.
- The maximum length of a relative pathname when path
or fd is the current working directory. The corresponding macro is
- 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
- 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
- If fd or path refers to a directory, then the
return value applies to all files in that directory.
- This returns nonzero if accessing filenames longer than
_POSIX_NAME_MAX generates an error. The corresponding macro is
- 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 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 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
- 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)
|fpathconf (), pathconf ()
Files with name lengths longer than the value returned for name
may exist in the given directory.
Some returned values may be huge; they are not suitable for allocating memory.
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