- Added comment to OS ass3.

os/ass3/fishbones.c

@@ -29,29 +29,30 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 	
 	do
 	{
-		/* Read 1 character from the pipe into 'c' here.
-		   Be sure to test that you have indeed read a character.
-		   If you get an error (read returns a negative value) or
-		   an end-of-file (read returns zero), end your program
-		   with an exit(1) */
-		
+        /* Read next character from pipe */
 		if( read(pipe_id[0], &c, 1) <= 0 )
 		{
-			fprintf(log1, "Child %d exited with error \n", myNumber);
-			fprintf(log2, "Child %d exited with error \n", myNumber);
-			fprintf(log3, "Child %d exited with error \n", myNumber);
+            /* Error while reading from the pipe, exit */
+			fprintf(log1, "Child %d read from pipe with error "
+                          "and exited \n", myNumber);
+			fprintf(log2, "Child %d read from pipe with error "
+                          "and exited \n", myNumber);
+			fprintf(log3, "Child %d read from pipe with error "
+                          "and exited \n", myNumber);
 			fclose(log1);
 			fclose(log2);
 			fclose(log3);
 			exit(1);
 		}
 		
+        /* Character read successfully, process it */
 		fprintf(log1, "Child %d read character %x: '%c'\n", myNumber, c, c);
 		fprintf(log2, "Child %d read character %x: '%c'\n", myNumber, c, c);
 		fprintf(log3, "Child %d read character %x: '%c'\n", myNumber, c, c);
 
 		if( c == 'P' )
         {
+                /* Decrease antidote level or exit the process */
 				if( !antidote )
 				{
 					fprintf(log1, "Child %d has no antidote for poison "
@@ -72,6 +73,7 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 		}
         else if( c == 'A' )
         {
+                /* Increase antidote level */
 				antidote++;
 				fprintf(log1, "Child %d finds antidote (now has %d) \n",
 				        myNumber, antidote);
@@ -82,6 +84,7 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 		}
 	} while( c != '\0' );
 	
+    /* Close logs and exit normally */
 	fprintf(log1, "Child %d normal exit \n", myNumber);
 	fprintf(log2, "Child %d normal exit \n", myNumber);
 	fprintf(log3, "Child %d normal exit \n", myNumber);
@@ -92,9 +95,9 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 }
 
 void
-signal_handler(int action)
+signal_handler(int signum)
 {
-    switch( action )
+    switch( signum )
     {
         case SIGINT:
             
@@ -134,15 +137,15 @@ main(int argc, char * argv[])
 		exit(1);
 	}	
 
-    //action.sa_handler = signal_handler;
+    action.sa_handler = signal_handler;
 
-    //if( sigaction(SIGINT, &action, NULL) < 0
-    //    || sigaction(SIGTERM, &action, NULL) < 0
-    //    || sigaction(SIGCHLD, &action, NULL) < 0 )
-    //{
-    //    perror("An error occured while binding the signal handlers \n");
-    //    exit(1);
-    //}
+    if( sigaction(SIGINT, &action, NULL) < 0
+        || sigaction(SIGTERM, &action, NULL) < 0
+        || sigaction(SIGCHLD, &action, NULL) < 0 )
+    {
+        perror("An error occured while binding the signal handlers \n");
+        exit(1);
+    }
     
 	while( (c = getchar()) )
 	{
@@ -165,16 +168,19 @@ main(int argc, char * argv[])
 		
 		if( c == 'q' )
 		{
+            /* Exit program */
 			break;
 		}
 		else if( c != 'f' )
 		{
+            /* Write character to pipe for child processes */
 			if( write(pipe_id[1], &c, 1) != 1 )
 			{
 				perror("Cannot write to pipe \n");
 				exit(1);
 			}
                
+            /* Wait for child process to 'eat poison' */
 			if( c == 'P' )
                 wait(NULL);
 		}
@@ -190,12 +196,15 @@ main(int argc, char * argv[])
 			switch( (child_id = fork()) )
 			{
 				case -1:
+                    /* An error occured while forking */
 					perror("Child could not be created \n");
 					exit(1);
 				case 0:
+                    /* Child process after fork: read from pipe */
 					gup(log1, log2, pipe_id, kiddoCount);
 					break;
 				default:
+                    /* Parent proces after fork: Print child's process id */
 					fprintf(log1, "Started child process %d with id %d \n",
                             kiddoCount, child_id);
 					fprintf(log2, "Started child process %d with id %d \n",
@@ -204,6 +213,7 @@ main(int argc, char * argv[])
 		}
 	}
     
+    /* Close logs and exit normally */
 	fprintf(log1, "Program exited normally \n");
 	fprintf(log2, "Program exited normally \n");
 	fclose(log1);