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AIX Version 4.3 Base Operating System and Extensions Technical Reference, Volume 1
pathconf or fpathconf Subroutine
Purpose
Retrieves file-implementation characteristics.
Library
Standard C Library (libc.a)
Syntax
#include <unistd.h>
long pathconf (Path, Name)
const char *Path;
int Name;
long fpathconf(FileDescriptor, Name)
int FileDescriptor, Name;
Description
The pathconf subroutine allows an application to determine the
characteristics of operations supported by the file system contained by the file named by the Path
parameter. 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 fpathconf subroutine allows an application to retrieve the
same information for an open file.
Parameters
Path |
Specifies the path name. |
FileDescriptor |
Specifies an open file descriptor. |
Name |
Specifies the configuration attribute to be queried. If this attribute is not applicable to the
file specified by the Path or FileDescriptor parameter, the pathconf subroutine
returns an error. Symbolic values for the Name parameter are defined in the unistd.h file:
- _PC_LINK_MAX
- Specifies the maximum number of links to the file.
- _PC_MAX_CANON
- Specifies the maximum number of bytes in a canonical input line. This value is applicable only
to terminal devices.
- _PC_MAX_INPUT
- Specifies the maximum number of bytes allowed in an input queue. This value is applicable only
to terminal devices.
- _PC_NAME_MAX
- Specifies the maximum number of bytes in a file name, not including a terminating null
character. This number can range from 14 through 255. This value is applicable only to a directory
file.
- _PC_PATH_MAX
- Specifies the maximum number of bytes in a path name, not including a terminating null
character.
- _PC_PIPE_BUF
- Specifies the maximum number of bytes guaranteed to be written atomically. This value is
applicable only to a first-in-first-out (FIFO).
- _PC_CHOWN_RESTRICTED
- Returns 0 if the use of the chown subroutine is restricted to a process with appropriate
privileges, and if the chown subroutine is restricted 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.
- _PC_NO_TRUNC
- Returns 0 if long component names are truncated. This value is applicable only to a directory
file.
- _PC_VDISABLE
- This is always 0. No disabling character is defined. This value is applicable only to a
terminal device.
Note: The _PC_FILESIZEBITS and PC_SYNC_IO flags apply to AIX Version 4.3 and later releases.
- _PC_FILESIZEBITS
- Returns the minimum number of bits required to hold the file system's maximum file size as a signed integer. The smallest value returned is 32.
- _PC_SYNC_IO
- Returns -1 if the file system does not support the
Synchronized Input and Output option. Any value other than -1 is returned if the file system
supports the option.
|
Notes: - If the Name parameter has a value of _PC_LINK_MAX, and if
the Path or FileDescriptor parameter refers to a directory, the value returned applies to
the directory itself.
- If the Name parameter has a value of _PC_NAME_MAX or
_PC_NO_TRUNC, and if the Path or FileDescriptor parameter refers to a directory, the
value returned applies to filenames within the directory.
- If the Name parameter has a value if _PC_PATH_MAX, and if
the Path or FileDescriptor parameter refers to a directory that is the working directory,
the value returned is the maximum length of a relative pathname.
- If the Name parameter has a value of _PC_PIPE_BUF, and if
the Path parameter refers to a FIFO special file or the FileDescriptor parameter refers to a
pipe or a FIFO special file, the value returned applies to the referenced object. If the Path or
FileDescriptor parameter refers to a directory, the value returned applies to any FIFO special file
that exists or can be created within the directory.
- If the Name parameter has a value of _PC_CHOWN_RESTRICTED,
and if the Path or FileDescriptor parameter refers to a directory, the value returned
applies to any files, other than directories, that exist or can be created within the directory.
Return Values
If the pathconf or fpathconf subroutine is successful, the
specified parameter is returned. Otherwise, a value of -1 is returned and the errno global variable
is set to indicate the error.
If the variable corresponding to the Name parameter has no limit for the Path parameter or
the FileDescriptor parameter, both the pathconf and fpathconf subroutines return a
value of -1 without changing the errno global variable.
Error Codes
The pathconf or fpathconf subroutine fails if the
following error occurs:
EINVAL |
The name parameter specifies an unknown or inapplicable characteristic. |
The pathconf subroutine can also fail if any of the following
errors occur:
EACCES |
Search permission is denied for a component of the path prefix. |
EINVAL |
The implementation does not support an association of the Name parameter with the
specified file. |
ENAMETOOLONG |
The length of the Path parameter string exceeds the PATH_MAX value. |
ENAMETOOLONG |
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 parameter points to an empty string. |
ENOTDIR |
A component of the path prefix is not a directory. |
ELOOP |
Too many symbolic links were encountered in resolving path. |
The fpathconf subroutine can fail if either of the following
errors occur:
EBADF |
The File Descriptor parameter is not valid. |
EINVAL |
The implementation does not support an association of the Name parameter with the
specified file. |
Implementation Specifics
These subroutines are part of Base Operating System (BOS) Runtime.
Related Information
The chown subroutine, confstr subroutine, sysconf subroutine.
Files,
Directories, and File Systems for Programmers, Subroutines Overview in AIX Version 4.3 General Programming Concepts: Writing and Debugging Programs.
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