gspool_jobmon(3) set a function to monitor changes to jobs


#include <gspool.h>

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

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

int gspool_procmon(const int fd)

void gspool_unsetmon(const int fd)


Unix and GNU/Linux

The gspool_jobmon() function is used to set the function fn to be called upon notification of any changes to the jobs list.

fd is a file descriptor previously returned by gspool_open.

fn is 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.


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

fd is a file descriptor previously returned by gspool_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 gspool_procmon is provided. This returns "XTWINAPI_JOBPROD" to indicate a change or changes to the job queue and "XTWINAPI_PTRPROD" to indicate a change or changes to the printer list. If there are changes to both, two or more messages will be sent, each of which should be decoded via separate gspool_procmon calls.

To cancel monitoring, invoke the routine


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


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


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 <>. There is NO WARRANTY, to the extent permitted by law.


John M Collins, Xi Software Ltd.