how signal works

[thaj]

Hi,
I want to know how the signal works in the following code. The signal is called for every true and false condition and quits the application also. I want to know how signal works in the following code. Can anyone pls. help me to explain this.

while (1) {
/* check for a file to process */
/* process files until no more exist */
if ((wms_input = FindInbound(input_file_dir,input_file_ext)) != (char *)NULL) {
signal(SIGTERM, SIG_IGN);
sleep(1); /* used to ensure that file is completely ftped */

if((fp = fopen(wms_input,"r")) == NULL)
{
sprintf(jnlmsg, "Cannot open file %s",wms_input);
ssw_jnlreq(0,"AP",INF,pgm_nm,1000,jnlmsg,0,0);
signal(SIGTERM, term_handler);
sprintf(target_fname, "%s.err.old", wms_input);
rename(wms_input, target_fname);
continue;
}
sprintf(jnlmsg, "Processing file %s",wms_input);
ssw_jnlreq(0,"AP",INF,pgm_nm,1000,jnlmsg,0,0);

proc_ret = process_wmsinput();

if (proc_ret == 1) {
sprintf(jnlmsg, "Bad File Cont:%s.err.old",wms_input);
ssw_jnlreq(0,"AP",INF,pgm_nm,1000,jnlmsg,0,0);
signal(SIGTERM, term_handler);
sprintf(target_fname, "%s.err.old", wms_input);
rename(wms_input, target_fname);
continue;
}
else if (proc_ret == -1) {
sprintf(target_fname, "%s.unp.old", wms_input);
unlink(target_fname);
rename(wms_input, target_fname);
sprintf(jnlmsg, "Processing %s complete",wms_input);
ssw_jnlreq(0,"AP",INF,pgm_nm,1000,jnlmsg,0,0);
signal(SIGTERM, term_handler);
}
else {
sprintf(target_fname, "%s.old", wms_input);
unlink(target_fname);
rename(wms_input, target_fname);
sprintf(jnlmsg, "Processing %s complete",wms_input);
ssw_jnlreq(0,"AP",INF,pgm_nm,1000,jnlmsg,0,0);
signal(SIGTERM, term_handler);
}


}
else sleep(sleep_interval);
}
exit (0);
}

int term_handler(sig)
int sig;
{
ssw_jnlreq(0,"AP",INF,pgm_nm,1000,"Received shutdown notification",0,0);

exit(0);
}