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pathconf(2)
NAME
pathconf, fpathconf - Retrieve file implementation characteristics
SYNOPSIS
#include <unistd.h>
long pathconf(
const char *path,
int name );
long fpathconf(
int filedes,
int name );
STANDARDS
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.
PARAMETERS
path Specifies the pathname. If the final component of path is a
symbolic link, it will be traversed and file name resolution will
continue.
filedes Specifies an open file descriptor.
name Specifies the configuration attribute to be queried.
DESCRIPTION
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>.
FILESIZEBITS (_PC_FILESIZEBITS)
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.
LINK_MAX (_PC_LINK_MAX)
The maximum number of links to the file.
If path or filedes refers to a directory, the value returned applies to
the directory itself.
MAX_CANON (_PC_MAX_CANON)
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.
MAX_INPUT (_PC_MAX_INPUT)
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.
NAME_MAX (_PC_NAME_MAX)
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.
PATH_MAX (_PC_PATH_MAX)
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.
PIPE_BUF (_PC_PIPE_BUF)
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.
_POSIX_ACL_EXTENDED (_PC_ACL_EXTENDED)
[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.
_POSIX_CHOWN_RESTRICTED (_PC_CHOWN_RESTRICTED)
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.
_POSIX_NO_TRUNC (_PC_NO_TRUNC)
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.
_POSIX_ASYNC_IO (_PC_ASYNC_IO)
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.)
_POSIX_PRIO_IO (_PC_PRIO_IO)
Prioritized input and output operations may be performed on the
specified file. Returns -1. (Prioritized I/O is not available on Tru64
UNIX systems.)
_POSIX_SYNC_IO (_PC_SYNC_IO)
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.)
_POSIX_VDISABLE (_PC_VDISABLE)
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.
RETURN VALUES
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.
ERRORS
If the pathconf() function fails, errno may be set to the following value:
[EACCES]
Search permission is denied for a component of the path prefix.
[ELOOP] Too many symbolic links were encountered in translating a pathname.
[EINVAL]
The name parameter is invalid.
[EFAULT]
[Tru64 UNIX] The path argument is an invalid address.
[ENAMETOOLONG]
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.
[ENOENT]
The named file does not exist or the path argument points to an
empty string.
[ENOTDIR]
A component of the path prefix is not a directory.
If the fpathconf() function fails, errno may be set to the following value:
[EINVAL]
The name parameter specifies an unknown or inapplicable
characteristic.
[EBADF] The filedes argument is not a valid file descriptor.
[EIO] [Tru64 UNIX] The named file has been revoked.
SEE ALSO
Standards: standards(5)
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