pathconf, fpathconf - Retrieve file implementation characteristics
#include <unistd.h>
long pathconf(
const char *path,
int name ); long fpathconf(
int filedes,
int name );
Interfaces documented on this reference page conform to
industry standards as follows:
fpathconf(), pathconf(): POSIX.1, XSH4.0, XSH4.2, XSH5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Specifies the pathname. If the final component of path is
a symbolic link, it will be traversed and file name resolution
will continue. Specifies an open file descriptor.
Specifies the configuration attribute to be queried.
The fpathconf() and pathconf() functions provide a method
for an application to determine the current value of a
configurable limit or option (variable) that is associated
with a file or directory.
For pathconf(), the path parameter points to the pathname
of a file or directory. Read, write, or execute permission
of the named file is not required, but all directories in
the path leading to the file must be searchable.
The following is a list of the system variables whose values
are returned by pathconf() and fpathconf() and the
symbolic constants (shown in parentheses) that are the
corresponding values used for the name parameter. The
variables come from either the <limits.h> or <unistd.h>
header file and the symbolic constants are defined in
<unistd.h>.
The minimum number of bits needed to represent as a signed
integer value the maximum size of a regular file that is
allowed in the specified directory. The maximum number of
links to the file.
If path or filedes refers to a directory, the value
returned applies to the directory itself. The maximum
number of bytes in a canonical input line.
The association of this variable name with the
specified file is guaranteed only when path or
filedes refers to a terminal file. The minimum
number of bytes for which space is available in an
input queue; therefore, the maximum number of bytes
a portable application may require to be typed as
input before reading them.
The association of this variable name with the
specified file is guaranteed only when path or
filedes refers to a terminal file. The maximum
number of bytes in a file name (not including a
terminating null).
If path or filedes refers to a directory, the value
returned applies to file names within the directory.
The association of this variable name with the
specified file is guaranteed only when path or
filedes refers to a directory. The maximum number
of bytes in a pathname (including a terminating
null).
If path or filedes refers to a directory, the value
returned is the maximum length of a relative pathname
when the specified directory is the working
directory.
The association of this variable name with the
specified file is guaranteed only when path or
filedes refers to a directory. The maximum number
of bytes guaranteed to be atomic when writing to a
pipe.
If path refers to a FIFO, or filedes refers to a
pipe or FIFO, the value returned applies to the
referenced object. If path or filedes refers to a
directory, the value returned applies to any FIFO
that exists or can be created within the directory.
The association of this variable name with the
specified file is not guaranteed if path or filedes
refers to any other type of file. [Tru64
UNIX] The Access Control List (ACL) processing
status value for the file. The return indicates if
an ACL can be set on the file and if ACL processing
is enabled for the file. The return does not indicate
if an ACL is set on the file.
Returns 1 if ACLs are supported and enabled for the
file. This indicates that ACLs can be set on the
file and that ACL checking and ACL inheritance are
enabled on the file.
Returns 0 if ACLs are supported for the file, but
are not enabled. This indicates that ACLs can be
set on the file, but that ACL checking and ACL
inheritance are not enabled on the file.
Returns -1 with errno set to [EINVAL] if ACLs are
not supported for the file. This indicates that
the filesystem containing the file does not support
ACLs. The use of chown() is restricted to a process
with appropriate privileges, and to changing
the group ID of a file only to the effective group
ID of the process or to one of its supplementary
group IDs.
If the path or filedes parameter refers to a directory,
the value returned applies to any files
(other than directories) that exist or can be
created within the directory. Returns 0 (zero) if
supplying a component name longer than allowed by
NAME_MAX will cause an error. Returns 1 if long
component names are truncated.
If path or filedes refers to a directory, the value
returned applies to file names within the directory.
The association of this variable name with the
specified file is guaranteed only when path or
filedes refers to a directory. Asynchronous I/O
may be performed for the specified file. Returns a
value other than -1 on all applicable files. (On
Tru64 UNIX systems, asynchronous I/O is supported
for all applicable files.) Prioritized input and
output operations may be performed on the specified
file. Returns -1. (Prioritized I/O is not available
on Tru64 UNIX systems.) Synchronous I/O may be
performed for the specified file. Returns a value
other than -1 on all applicable files. (On Tru64
UNIX systems, synchronous I/O is supported for all
applicable files.) A character value used to disable
terminal special characters.
The association of this variable name with the
specified file is guaranteed only when path or
filedes refers to a terminal file.
Upon successful completion, the pathconf() or fpathconf()
function returns the specified parameter.
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 pathconf() function fails, errno may be set to the
following value: Search permission is denied for a component
of the path prefix. Too many symbolic links were
encountered in translating a pathname. The name parameter
is invalid. [Tru64 UNIX] The path argument is an invalid
address. The length of the path string exceeds PATH_MAX
or a pathname component is longer than NAME_MAX.
Pathname resolution of a symbolic link produced an
intermediate result whose length exceeds PATH_MAX.
The named file does not exist or the path argument
points to an empty string. A component of the path
prefix is not a directory.
If the fpathconf() function fails, errno may be set to the
following value: The name parameter specifies an unknown
or inapplicable characteristic. The filedes argument is
not a valid file descriptor. [Tru64 UNIX] The named file
has been revoked.
Standards: standards(5)
pathconf(2)
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