Startpunkten

Lab1/lab1.c

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+/* ===========================================
+*   Lab 1 i C & UNIX
+*  ==========================================
+*      Semaforer
+*  ==========================================
+*   Christian Ohlsson, di7chro@cse.kau.se
+*   Karlstads universitet
+*   991110
+* ===========================================
+*/
+
+#include <signal.h>
+#include <stdio.h>
+
+#define WAITTIME 3
+#define PERMS 0000
+
+int P(char *name){
+   while(creat(name,PERMS) == -1) ;
+}
+void V(char *name){
+   unlink(name);
+}
+void handleSig(){
+   V("A");
+   V("B");
+   V("C");
+   exit(0);
+}
+void A(){
+   while(1) {
+       P("A"); 
+       write(1, "A", 1);
+       V("B");
+       sleep(WAITTIME);
+       P("A");
+       write(1, "A", 1);
+       V("C");
+       sleep(WAITTIME);
+   }
+}
+void B(){ 
+   while(1) {
+       P("B");
+       write(1, "B\n", 2);
+       V("A");
+   }
+} 
+void C() {
+   while(1) {
+       P("C");
+       write(1, "C\n", 2);
+       V("A");
+   }
+}
+int main() {
+   int pidA, pidB, stat;
+   if((signal(SIGINT,  handleSig)) ==  SIG_ERR) {
+       perror("\nCould not initialize signals\n"); 
+       exit(0);
+   }
+   signal(SIGTERM, SIG_IGN); 
+   P("B");
+   P("C");
+   if((pidA=fork()) > 0) {
+      if((pidB=fork()) > 0) {
+         A();
+         waitpid(pidA, &stat, 0);
+         waitpid(pidB, &stat, 0);
+      }
+      if(pidB == 0)
+         C();
+   }
+   if(pidA == 0)
+      B();
+   perror("\nCould not fork.\n"); 
+   return 0;
+}