pathconf.2 (2010 09)

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pathconf(2) pathconf(2)
8. _POSIX_CHOWN_RESTRICTED
is defined if the privilege group
PRIV_GLOBAL has been
granted the
CHOWN privilege (see getprivgrp (2) and chown(2)). In all other cases,
_POSIX_CHOWN_RESTRICTED
is undefined and
pathconf() or fpathconf() returns −1
without changing
errno. To determine if
chown() can be performed on a file, it is simplest
to attempt the
chown() operation and check the return value for failure or success.
9.
_POSIX_SYNC_IO
, when defined, determines whether synchronized IO operations may be
performed for the associated file (see open(2)). If path or fildes refers to a directory, it is
unspecified whether or not the implementation supports an association of the variable name
with the specified file.
10. For file systems that are not large file enabled, the
_PC_FILESIZEBITS
return value will be
less than or equal to 32. For file systems that are large file enabled, the
_PC_FILESIZEBITS
return value will be between 33 and 63.
11.
_POSIX_ASYNC_IO
, when defined, determines whether asynchronous I/O operations may be
performed for the associated file.
12.
_POSIX_PRIO_IO
, when defined, determines whether prioritized I/O is supported for the
associated file.
If the variable corresponding to name is not defined for path or fildes , the
pathconf() and fpath-
conf() functions succeed and return a value of −1, without changing the value of errno
.
Upon any other successful completion, these functions return the value of the named variable with
respect to the specified file or directory, as described above.
Otherwise, a value of − 1 is returned and
errno is set to indicate the error.
ERRORS
The
pathconf() and fpathconf() fail if any of the following conditions are encountered:
[EACCES] A component of the path prefix denies search permission.
[EBADF] The fildes argument is not a valid open file descriptor.
[EFAULT] path points outside the allocated address space of the process.
[EINVAL] The value of name is not valid or the implementation does not support an
association of the variable name with the specified file.
[ELOOP] Too many symbolic links were encountered in translating path .
[ENAMETOOLONG] The length of the specified path name exceeds
PATH_MAX bytes, or the
length of a component of the path name exceeds
NAME_MAX bytes while
_POSIX_NO_TRUNC is in effect.
[ENOENT] The file named by path does not exist (for example, path is null, or a com-
ponent of path does not exist).
[ENOTDIR] A component of the path prefix is not a directory.
EXAMPLES
The following example sets val to the value of
MAX_CANON for the device file being used as the standard
input. If the standard input is a terminal, this value is the maximum number of input characters that
can be entered on a single input line before typing the newline character:
if (isatty(0))
val = fpathconf(0, _PC_MAX_CANON);
The following code segment shows two calls to pathconf . The first determines whether a file name longer
than NAME_MAX bytes will be truncated to NAME_MAX bytes in the /tmp directory. If so, the second call
is made to determine the actual value of NAME_MAX so that an error can be printed if a user-supplied file
name stored in filebuf will be truncated in this directory:
extern int errno;
char *filebuf;
errno = 0; /* reset errno */
if ( pathconf("/tmp" _PC_NO_TRUNC) == -1 ) {
/* _POSIX_NO_TRUNC is not in effect for this directory */
if (strlen(filebuf) > pathconf("/tmp", PC_NAME_MAX)) {
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