User`s guide

Programming with VISA 3
Agilent VISA User’s Guide 91
When the session holding the exclusive lock unlocks the
resource via the viUnlock function, all the sessions sharing
the lock again have all the access privileges associated with
the shared lock.
/* lockshr.c
This example program queries a GPIB device for
an identification string and prints the results.
Note that you must change the address. */
#include <visa.h>
#include <stdio.h>
void main () {
ViSession defaultRM, vi;
char buf [256] = {0};
char lockkey [256] = {0};
/* Open session to GPIB device at address 22 */
viOpenDefaultRM (&defaultRM);
viOpen (defaultRM, "GPIB0::22::INSTR",
VI_NULL,VI_NULL,&vi);
/* acquire a shared lock so only this process
and processes that we know about can access
this resource */
viLock (vi, VI_SHARED_LOCK, 2000, VI_NULL,
lockkey);
/* at this time, we can make 'lockkey'
available to other processes that we know
about. This can be done with shared memory or
other inter-process communication methods.
These other processes can then call
"viLock(vi,VI_SHARED_LOCK, 2000, lockkey,
lockkey)" and they will also have access to
this resource. */
/* Initialize device */
viPrintf (vi, "*RST\n");