NAME

io_timeout_ctl() − establish a time limit for I/O operations

SYNOPSIS

#include <dvio.h>

int io_timeout_ctl(int eid, long time);

DESCRIPTION

io_timeout_ctl() assigns a timeout value to the specified eid (entity identifier).  eid is an entity identifier of an open HP-IB raw bus, auto-addressed, Centronics-compatible parallel, or GPIO device file obtained from an open(), dup(), fcntl(), or creat() call.  time is a long integer value specifying the length of the timeout in microseconds.  A value of 0 for time specifies no timeout (infinity). 

This timeout applies to future read and write requests on this eid. If a read or write request does not complete within the specified time limit, the request is aborted and returns an error indication. If an operation is aborted due to a timeout, errno is set to ETIMEDOUT. 

Although the timeout value is specified in microseconds, the resolution of the timeout is system-dependent.  For example, a particular system might have a resolution of 10 milliseconds, in which case the specified timeout value is rounded up to the next 10 msec boundary.  A timeout value of zero means that the system never causes a timeout.  When a file is opened, a zero timeout value is assigned by default. 

Entity identifiers for the same device file obtained by separate open() calls have their own timeout values associated with them.  Entity identifiers for the same device file obtained by dup() or inherited by a fork() call share the same timeout value.  In the latter case, if one process changes the timeout, the new timeout is in effect for all such eids.

RETURN VALUE

io_timeout_ctl() returns 0 (zero) if successful, or −1 if an error was encountered. 

ERRORS

io_timeout_ctl() fails under the following circumstances, and sets errno (see errno(2)) to the value indicated:

[EBADF] eid does not refer to an open file. 

[ENOTTY] eid does not refer to a channel device file. 

AUTHOR

io_timeout_ctl() was developed by HP. 

Hewlett-Packard Company  —  HP-UX Release 10.20:  July 1996