pathconf(2)
NAME
fpathconf, pathconf - get configurable pathname variables
SYNOPSIS
#include <unistd.h>
long fpathconf(int fildes, int name);
long pathconf(const char *path, int name);
DESCRIPTION
The fpathconf() and pathconf() functions provide a method
for the application to determine the current value of a con-
figurable limit or option ( variable ) that is associated
with a file or directory.
For pathconf(), the path argument points to the pathname of
a file or directory.
For fpathconf(), the fildes argument is an open file
descriptor.
The name argument represents the variable to be queried
relative to that file or directory. The variables in the
following table come from <limits.h> or <unistd.h> and the
symbolic constants, defined in <unistd.h>, are the
corresponding values used for name:
_________________________________________________________________
| Variable | Value of name | Notes |
|________________________|________________________|______________|
| FILESIZEBITS | _PC_FILESIZEBITS | 3,4 |
|________________________|________________________|______________|
| LINK_MAX | _PC_LINK_MAX | 1 |
|________________________|________________________|______________|
| MAX_CANON | _PC_MAX_CANON | 2 |
|________________________|________________________|______________|
| MAX_INPUT | _PC_MAX_INPUT | 2 |
|________________________|________________________|______________|
| NAME_MAX | _PC_NAME_MAX | 3,4 |
|________________________|________________________|______________|
| PATH_MAX | _PC_PATH_MAX | 4,5 |
|________________________|________________________|______________|
| PIPE_BUF | _PC_PIPE_BUF | 6 |
|________________________|________________________|______________|
| XATTR_ENABLED | _PC_XATTR_ENABLED | 1 |
|________________________|________________________|______________|
| XATTR_EXISTS | _PC_XATTR_EXISTS | 1 |
|________________________|________________________|______________|
| _POSIX_CHOWN_RESTRICTED| _PC_CHOWN_RESTRICTED | 7 |
|________________________|________________________|______________|
| _POSIX_NO_TRUNC | _PC_NO_TRUNC | 3,4 |
|________________________|________________________|______________|
| _POSIX_VDISABLE | _PC_VDISABLE | 2 |
|________________________|________________________|______________|
| _POSIX_ASYNC_IO | _PC_ASYNC_IO | 8 |
|________________________|________________________|______________|
| _POSIX_PRIO_IO | _PC_PRIO_IO | 8 |
|________________________|________________________|______________|
| _POSIX_SYNC_IO | _PC_SYNC_IO | 8 |
|________________________|________________________|______________|
Notes:
1. If path or fildes refers to a directory, the value
returned applies to the directory itself.
2. If path or fildes does not refer to a terminal file, it
is unspecified whether an implementation supports an
association of the variable name with the specified file.
3. If path or fildes refers to a directory, the value
returned applies to filenames within the directory.
4. If path or fildes does not refer to a directory, it is
unspecified whether an implementation supports an associ-
ation of the variable name with the specified file.
5. If path or fildes refers to a directory, the value
returned is the maximum length of a relative pathname
when the specified directory is the working directory.
6. If path refers to a FIFO, or fildes refers to a pipe or
FIFO, the value returned applies to the referenced
object. If path or fildes refers to a directory, the
value returned applies to any FIFO that exists or can be
created within the directory. If path or fildes refers
to any other type of file, it is unspecified whether an
implementation supports an association of the variable
name with the specified file.
7. If path or fildes refers to a directory, the value
returned applies to any files, other than directories,
that exist or can be created within the directory.
8. If path or fildes refers to a directory, it is unspeci-
fied whether an implementation supports an association of
the variable name with the specified file.
RETURN VALUES
If name is an invalid value, both pathconf() and fpathconf()
return -1 and errno is set to indicate the error.
If the variable corresponding to name has no limit for the
path or file descriptor, both pathconf() and fpathconf()
return -1 without changing errno. If the implementation
needs to use path to determine the value of name and the
implementation does not support the association of name with
the file specified by path, or if the process did not have
appropriate privileges to query the file specified by path,
or path does not exist, pathconf() returns -1 and errno is
set to indicate the error.
If the implementation needs to use fildes to determine the
value of name and the implementation does not support the
association of name with the file specified by fildes, or if
fildes is an invalid file descriptor, fpathconf() will
return -1 and errno is set to indicate the error.
Otherwise pathconf() or fpathconf() returns the current
variable value for the file or directory without changing
errno. The value returned will not be more restrictive than
the corresponding value available to the application when it
was compiled with the implementation's <limits.h> or
<unistd.h>.
ERRORS
The pathconf() function will fail if:
EINVAL
The value of name is not valid.
ELOOP Too many symbolic links were encountered in resolving
path.
The pathconf() function may fail if:
EACCES
Search permission is denied for a component of the
path prefix.
EINVAL
The implementation does not support an association of
the variable name with the specified file.
ENAMETOOLONG
The length of the path argument exceeds PATH_MAX or a
pathname component is longer than NAME_MAX.
ENAMETOOLONG
Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds PATH_MAX.
ENOENT
A component of path does not name an existing file or
path is an empty string.
ENOTDIR
A component of the path prefix is not a directory.
The fpathconf() function will fail if:
EINVAL
The value of name is not valid.
The fpathconf() function may fail if:
EBADF The fildes argument is not a valid file descriptor.
EINVAL
The implementation does not support an association of
the variable name with the specified file.
ATTRIBUTES
See attributes(5) for descriptions of the following attri-
butes:
_______________________________________________________________
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
| ____________________________|________________________________|_
| Interface Stability | fpathconf() is Standard; path|
| | conf() is Stable |
|_____________________________|________________________________|
| MT-Level | pathconf() is Async-Signal-Safe|
|_____________________________|________________________________|
SEE ALSO
sysconf(3C), limits(4), attributes(5), standards(5)
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