gbatch_jobmon - monitor changes to the job queue

# NAME

gbatch_jobmon - monitor changes to the job queue

# SYNOPSIS

#include <gbatch.h>

int gbatch_jobmon(const int fd, void (*fn)(const int))

int gbatch_setmon(const int fd, HWND hWnd, UINT wMsg)

int gbatch_procmon(const int fd)

void gbatch_unsetmon(const int fd)

# DESCRIPTION

## Unix and GNU/Linux

The function gbatch_jobmon() is used to set a function to monitor changes to the job queue.

fd is a file descriptor which was previously returned by a successful call to `gbatch_open(3)`.

fn is a pointer to a function which must be declared as returning void and taking one `const int` argument. Alternatively, this may be `NULL` to cancel monitoring.

The function fn will be called upon each change to the job list. The argument passed will be fd. Note that any changes to the job queue are reported (including changes on other hosts whose details are passed through) as the API does not record which jobs the user is interested in.

## Windows

The gbatch_setmon routine may be used to monitor changes to the job queue or variable list. Its parameters are as follows.

fd is a file descriptor previously returned by gbatch_open.

hWnd is a windows handle to which messages should be sent.

wMsg is the message id to be passed to the window (`WM_USER` or a constant based on this is suggested).

To decode the message, the gbatch_procmon is provided. This returns `XBWINAPI_JOBPROD` to indicate a change or changes to the job queue and `XBWINAPI_VARPROD` to indicate a change or changes to the variable list. If there are changes to both, two or more messages will be sent, each of which should be decoded via separate gbatch_procmon calls.

To cancel monitoring, invoke the routine

     gbatch_unsetmon(fd)

If no monitoring is in progress, or the descriptor is invalid, this call is just ignored.

# RETURN VALUES

The function gbatch_jobmon() returns 0 if successful otherwise the error code `XBAPI_INVALID_FD` if the file descriptor is invalid. Invalid fn parameters will not be detected and the application program will probably crash.

# EXAMPLE

     void note_mod(const int fd)  {
         job_changes++;
     }
     . . .

     gbatch_jobmon(fd, note_mod);
     . . .

     if (job_changes) { /* handle changes */
     . . .
     }

# SEE ALSO

`gbatch_close(3)`, `gbatch_open(3)`, `gbatch_varmon(3)`.

# COPYRIGHT

Copyright (c) 2009 Free Software Foundation, Inc. This is free software. You may redistribute copies of it under the terms of the GNU General Public License <http://www.gnu.org/licenses/gpl.html>. There is NO WARRANTY, to the extent permitted by law.

# AUTHOR

John M Collins, Xi Software Ltd.