pathconf()

Return the value of a configurable limit

Synopsis:

#include <unistd.h>

long pathconf( const char* path, 
               int name );

Arguments:

path: The name of the file whose limit you want to get.
name: The name of the configurable limit; see below.

Library:

libc

Use the -l c option to qcc to link against this library. This library is usually included automatically.

Description:

The pathconf() function returns a value of a configurable limit indicated by name, which is associated with the filename given in path.

Configurable limits are defined in <confname.h>, and include at least the following values:

_PC_2_SYMLINKS: 1 if symbolic links can be created, 0 if not.
_PC_ALLOC_SIZE_MIN: Minimum number of bytes of storage actually allocated for any portion of a file.
_PC_ASYNC_IO: Defined if asynchronous I/O is supported for the file.
_PC_CASE_PRESERVING: (QNX Neutrino 7.0 or later) 1 if the filesystem preserves the case in file names, or 0 if it doesn't. If this function indicates an error of EINVAL, you shouldn't make any assumptions about the filesystem's behavior.
_PC_CASE_SENSITIVE: (QNX Neutrino 7.0 or later) 1 if the filesystem is sensitive to the case in file names, or 0 if it isn't. If this function indicates an error of EINVAL, you shouldn't make any assumptions about the filesystem's behavior.
_PC_CHOWN_RESTRICTED: If defined (not -1), indicates that the use of the chown() function is restricted to a process with root privileges, and to changing the group ID of a file to the effective group ID of the process or to one of its supplementary group IDs.
_PC_FILESIZEBITS: Minimum number of bits needed to represent, as a signed integer value, the maximum size of a regular file allowed in the specified directory.
_PC_LINK_DIR: Defined (not -1) if the filesystem permits the unlinking of a directory.
_PC_LINK_MAX: Maximum value of a file's link count.
_PC_MAX_CANON: Maximum number of bytes in a terminal's canonical input buffer (edit buffer).
_PC_MAX_INPUT: Maximum number of bytes in a terminal's raw input buffer.
_PC_NAME_MAX: Maximum number of bytes in a file name (not including the terminating null).
_PC_NO_TRUNC: If defined (not -1), indicates that the use of pathname components longer than the value given by _PC_NAME_MAX will generate an error.
_PC_PATH_MAX: Maximum number of bytes in a pathname (including the terminating null).
_PC_PIPE_BUF: Maximum number of bytes that can be written atomically when writing to a pipe.
_PC_PRIO_IO: Defined (not -1) if prioritized I/O is supported for the file.
_PC_REC_INCR_XFER_SIZE: Recommended increment for file transfer sizes between the _PC_REC_MIN_XFER_SIZE and _PC_REC_MAX_XFER_SIZE values.
_PC_REC_MAX_XFER_SIZE: Maximum recommended file transfer size.
_PC_REC_MIN_XFER_SIZE: Minimum recommended file transfer size.
_PC_REC_XFER_ALIGN: Recommended file transfer buffer alignment.
_PC_SYMLINK_MAX: Maximum length (in bytes) of a symbolic link name.
_PC_SYMLOOP_MAX: Maximum length of a symbolic link chain. This is the maximum number of symbolic links that can be reliably traversed when resolving a pathname in the absence of a loop.
_PC_SYNC_IO: Defined (not -1) if synchronous I/O is supported for the file.
_PC_VDISABLE: If defined (not -1), this is the character value which can be used to individually disable special control characters in the termios control structure.

Returns:

The requested configurable limit, or -1 if an error occurs (errno is set).

Errors:

EACCES: Search permission is denied for a component of path.
EINVAL: The name argument is invalid, or the indicated limit isn't supported.
ELOOP: Too many levels of symbolic links or prefixes.
ENAMETOOLONG: The path argument, or a component of path, is too long.
ENOENT: The file doesn't exist.
ENOSYS: The pathconf() function isn't implemented for the filesystem underlying the path specified in path.
ENOTDIR: A component of the path prefix isn't a directory.

Examples:

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int main( void )
  {
    long value;

    value = pathconf( "/dev/con1", _PC_MAX_INPUT );
    printf( "Input buffer size is %ld bytes\n",
        value );
    return EXIT_SUCCESS;
  }

Classification:

POSIX 1003.1

Safety:
Cancellation point	Yes
Interrupt handler	No
Signal handler	Yes
Thread	Yes