FPATHCONF(2) System Calls FPATHCONF(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 determine the current value of a
configurable 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 |
+----------------------------+--------------------------+-------+
|{ACL_ENABLED} | _PC_ACL_ENABLED | 10 |
+----------------------------+--------------------------+-------+
|{FILESIZEBITS} | _PC_FILESIZEBITS | 3,4 |
+----------------------------+--------------------------+-------+
|{LINK_MAX} | _PC_LINK_MAX | 1 |
+----------------------------+--------------------------+-------+
|{MAX_CANON} | _PC_MAX_CANON | 2 |
+----------------------------+--------------------------+-------+
|{MAX_INPUT} | _PC_MAX_INPUT | 2 |
+----------------------------+--------------------------+-------+
|{MIN_HOLE_SIZE} | _PC_MIN_HOLE_SIZE | 11 |
+----------------------------+--------------------------+-------+
|{NAME_MAX} | _PC_NAME_MAX | 3, 4 |
+----------------------------+--------------------------+-------+
|{PATH_MAX} | _PC_PATH_MAX | 4,5 |
+----------------------------+--------------------------+-------+
|{PIPE_BUF} | _PC_PIPE_BUF | 6 |
+----------------------------+--------------------------+-------+
|{POSIX_ALLOC_SIZE_MIN} | _PC_ALLOC_SIZE_MIN | |
+----------------------------+--------------------------+-------+
|{POSIX_REC_INCR_XFER_SIZE} | _PC_REC_INCR_XFER_SIZE | |
+----------------------------+--------------------------+-------+
|{POSIX_REC_MAX_XFER_SIZE} | _PC_REC_MAX_XFER_SIZE | |
+----------------------------+--------------------------+-------+
|{POSIX_REC_MIN_XFER_SIZE} | _PC_REC_MIN_XFER_SIZE | |
+----------------------------+--------------------------+-------+
|{POSIX_REC_XFER_ALIGN} | _PC_REC_XFER_ALIGN | |
+----------------------------+--------------------------+-------+
|{SYMLINK_MAX} | _PC_SYMLINK_MAX | 4, 9 |
+----------------------------+--------------------------+-------+
|{XATTR_ENABLED} | _PC_XATTR_ENABLED | 1 |
+----------------------------+--------------------------+-------+
|{SATTR_ENABLED} | _PC_SATTR_ENABLED | |
+----------------------------+--------------------------+-------+
|{XATTR_EXISTS} | _PC_XATTR_EXISTS | 1 |
+----------------------------+--------------------------+-------+
|{SATTR_EXISTS} | _PC_SATTR_EXISTS | |
+----------------------------+--------------------------+-------+
|{ACCESS_FILTERING} | _PC_ACCESS_FILTERING | 12 |
+----------------------------+--------------------------+-------+
|_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 |
+----------------------------+--------------------------+-------+
|_POSIX_TIMESTAMP_RESOLUTION | _PC_TIMESTAMP_RESOLUTION | 1 |
+----------------------------+--------------------------+-------+


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 association
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 unspecified
whether an implementation supports an association of the
variable name with the specified file.

9. If path or fildes refers to a directory, the value returned is
the maximum length of the string that a symbolic link in that
directory can contain.

10. If path or fildes refers to a file or directory in a file
system that supports ACLs, the value returned is the bitwise
inclusive OR of the following flags associated with ACL types
supported by the file system; otherwise 0 is returned.

_ACL_ACE_ENABLED
The file system supports ACE ACLs.


_ACL_ACLENT_ENABLED
The file system supports UFS aclent ACLs.


11. If a filesystem supports the reporting of holes (see lseek(2),
pathconf() and fpathconf() return a positive number that
represents the minimum hole size returned in bytes. The
offsets of holes returned will be aligned to this same value.
A special value of 1 is returned if the filesystem does not
specify the minimum hole size but still reports holes.

12. If path or fildes refers to a directory and the file system in
which the directory resides supports access filtering, a non-
zero value is returned. Otherwise, 0 is returned.

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 pathconf() needs to use path to determine the value of name and
pathconf() 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 fpathconf() needs to use fildes to determine the value of name and
fpathconf() does not support the association of name with the file
specified by fildes, or if fildes is an invalid file descriptor,
fpathconf() returns -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 <limits.h> or <unistd.h>.

ERRORS


The pathconf() function will fail if:

EINVAL
The value of name is not valid.


ELOOP
A loop exists in symbolic links encountered during resolution
of the path argument.


The fpathconf() function will fail if:

EINVAL
The value of name is not valid.


The pathconf() function may fail if:

EACCES
Search permission is denied for a component of the path
prefix.


EINVAL
An association of the variable name with the specified
file is not supported.


ENAMETOOLONG
The length of the path argument exceeds {PATH_MAX} or a
pathname component is longer than {NAME_MAX}.


ENAMETOOLONG
As a result of encountering a symbolic link in resolution
of the path argument, the length of the substituted
pathname string exceeded {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 may fail if:

EBADF
The fildes argument is not a valid file descriptor.


EINVAL
An association of the variable name with the specified file is
not supported.


USAGE


The {SYMLINK_MAX} variable applies only to the fpathconf() function.

ATTRIBUTES


See attributes(5) for descriptions of the following attributes:


+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Committed |
+--------------------+-------------------+
|MT-Level | Async-Signal-Safe |
+--------------------+-------------------+
|Standard | See standards(5). |
+--------------------+-------------------+

SEE ALSO


lseek(2), confstr(3C), limits.h(3HEAD), sysconf(3C), attributes(5),
standards(5)


September 1, 2009 FPATHCONF(2)