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/*
* sample asynchronous outboard module.
*
* uses a signal to ask to be woken after a certain delay.
* if a given file has been changed, reimport the data.
*
* see watchfile.mdf, which must be loaded before this can be run.
* also see Makefile_architecture.name for how to compile this.
*/
#include <dx/dx.h>
#include <unistd.h>
#include <signal.h>
#include <stdio.h>
#include <sys/stat.h>
static Pointer id = NULL;
static time_t lastchanged;
static int seconds;
static char filename[1024];
/*
* this routine is called each time the alarm signal is
* issued.
*/
void signalcatch()
{
struct stat Buffer;
time_t changed;
/* stat the file to find out its last modification time */
if (stat(filename, &Buffer) == 0)
{
/* the last time the file was changed */
changed = Buffer.st_mtime;
/* compare to the last time the file was checked */
if (lastchanged != changed)
{
/* the file has changed. Rerun the main program. */
DXReadyToRun(id);
}
/* else the file hasn't changed since last time we checked */
else
{
/* go back to sleep for some seconds, but first reset the
* alarm */
signal(SIGALRM, signalcatch);
alarm(seconds);
}
}
}
Error
m_WatchFile(Object *in, Object *out)
{
struct stat Buffer;
char *file;
/* the first input is the filename to check */
if (!in[0])
{
DXSetError(ERROR_MISSING_DATA,"missing filename");
return ERROR;
}
if (!DXExtractString(in[0], &file))
{
DXSetError(ERROR_BAD_PARAMETER,"filename must be a string");
return ERROR;
}
/* put the filename into a static global variable */
strcpy(filename,file);
/* the second input is the number of seconds to wait between checks */
/* the default is 10 seconds */
if (!in[1])
seconds = 10;
else
{
if (!DXExtractInteger(in[1], &seconds))
{
DXSetError(ERROR_BAD_PARAMETER,"seconds must be an integer");
return ERROR;
}
}
/* the first time through, get the module id for the DXReadyToRun call */
if (!id) {
id = DXGetModuleId();
if (!id) {
out[0] = NULL;
return ERROR;
}
}
/* get the last modification time of the file */
if (stat(filename, &Buffer) != 0) {
DXSetError(ERROR_BAD_PARAMETER,"file %s not found", filename);
return ERROR;
}
lastchanged = Buffer.st_mtime;
/* import the data from the file */
out[0] = DXImportDX(filename, NULL, NULL, NULL, NULL);
/* set the alarm for the next wakeup */
signal(SIGALRM, signalcatch);
alarm(seconds);
return OK;
}
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