- Implemented signals in OS ass3.

os/ass3/fishbones.c

@@ -6,6 +6,8 @@
 #include <errno.h>
 #include <signal.h>
 
+static pid_t parent_pid;
+
 /*
  * Read from pipe (child processes only).
  */
@@ -22,49 +24,47 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 	fprintf(log1, "This is child number %d\n", myNumber);
 	fprintf(log2, "This is child number %d\n", myNumber);
 	
-	/* just for sure - open one more log file .... */
-	
+	/* Open a line buffered log. */
 	log3 = fopen("child.log3", "wt+");
 	setvbuf(log3, NULL, _IOLBF, BUFSIZ);
-	/* log3 is line buffered - a line of output is written 
-	   immediately on encountering an end-of-line */
+
 	fprintf(log3, "This is child number %d\n", myNumber);
 	
 	do
 	{
-        /* Read next character from pipe */
+		/* Read next character from pipe */
 		if( read(pipe_id[0], &c, 1) <= 0 )
 		{
-            /* Error while reading from the pipe, exit */
+			/* Error while reading from the pipe, exit */
 			fprintf(log1, "Child %d read from pipe with error "
-                          "and exited \n", myNumber);
+			              "and exited \n", myNumber);
 			fprintf(log2, "Child %d read from pipe with error "
-                          "and exited \n", myNumber);
+			              "and exited \n", myNumber);
 			fprintf(log3, "Child %d read from pipe with error "
-                          "and exited \n", myNumber);
+			              "and exited \n", myNumber);
 			fclose(log1);
 			fclose(log2);
 			fclose(log3);
 			exit(1);
 		}
 		
-        /* Character read successfully, process it */
+		/* 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 */
+		{
+				/* Decrease antidote level or exit the process */
 				if( !antidote )
 				{
 					fprintf(log1, "Child %d has no antidote for poison "
-                                  "and will exit \n", myNumber);
+					              "and will exit \n", myNumber);
 					fprintf(log2, "Child %d has no antidote for poison "
-                                  "and will exit \n", myNumber);
+					              "and will exit \n", myNumber);
 					fprintf(log3, "Child %d has no antidote for poison "
-                                  "and will exit \n", myNumber);
-                    break;
+					              "and will exit \n", myNumber);
+					break;
 				}
 				else
 				{
@@ -72,11 +72,11 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 					fprintf(log1, "antidote used (%d left) \n", antidote);
 					fprintf(log2, "antidote used (%d left) \n", antidote);
 					fprintf(log3, "antidote used (%d left) \n", antidote);
-                }
+				}
 		}
-        else if( c == 'A' )
-        {
-                /* Increase antidote level */
+		else if( c == 'A' )
+		{
+				/* Increase antidote level */
 				antidote++;
 				fprintf(log1, "Child %d finds antidote (now has %d) \n",
 				        myNumber, antidote);
@@ -87,7 +87,7 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 		}
 	} while( c != '\0' );
 	
-    /* Close logs and exit normally */
+	/* 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);
@@ -103,18 +103,34 @@ static void gup(FILE * log1, FILE * log2, int pipe_id[2], int myNumber)
 void
 signal_handler(int signum)
 {
-    switch( signum )
-    {
-        case SIGINT:
-            
-            break;
-        case SIGTERM:
-            
-            break;
-        case SIGCHLD:
-            
-            break;
-    }
+	char *sig = "TERM";
+	pid_t pid;
+
+	switch( signum )
+	{
+		case SIGINT:
+			sig = "INT";
+		case SIGTERM:
+			if( (pid = getpid()) == parent_pid )
+			{	
+				printf("Parent process received SIG%s and will exit \n", sig);
+			}
+			else
+			{
+				printf("Process with id %d received SIG%s and will exit \n",
+				       pid, sig);
+			}
+			exit(1);
+		case SIGCHLD:
+			puts("Parent process received SIGCHLD");
+			pid = wait(NULL);
+			printf("Child with id %d exited \n", pid);
+			break;
+		default:
+			puts("This handler is unapplicable for this type of signal");
+	}
+	
+	errno = 0;
 }
 
 /*
@@ -126,38 +142,54 @@ main(int argc, char * argv[])
 	FILE * log1;
 	FILE * log2;
 	char c;
-	int kiddoCount = 0, pipe_id[2];//, i = 1;
-	struct sigaction action;
-    
+	int kiddoCount = 0, pipe_id[2];
+	struct sigaction action = {.sa_handler = signal_handler};
+	
+	/* Save parent process id for signal handler */
+	parent_pid = getpid();
+
+	/* Open one buffered and one unbuffered log */
 	printf("argc: %d\n", argc);
 	log1 = fopen("child.log1", "wt+");
 	log2 = fopen("child.log2", "wt+");
 	setvbuf(log2, NULL, _IONBF, BUFSIZ);
-	/* So log1 is buffered; log2 is not buffered, which means that output
-	 * to log2 is written immediately. */
 	
 	/* Create pipe, exit with error on failure */
-    if( pipe(pipe_id) )
+	if( pipe(pipe_id) )
 	{
 		fprintf(stderr, "Error %d occured while creating the pipe \n",
-                errno);
+		        errno);
 		exit(1);
 	}	
-    
-    /* Bind signal handlers */
-    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);
-    }
-    
-    /* Keep reading input */
+	
+	/* Bind signal handlers */
+	if( sigaction(SIGINT, &action, NULL)
+		+ sigaction(SIGTERM, &action, NULL)
+		+ sigaction(SIGCHLD, &action, NULL) < 0 )
+	{
+		perror("An error occured while binding the signal handlers \n");
+		exit(1);
+	}
+	
+	/* Keep reading input */
 	while( (c = getchar()) )
 	{
+		if( c == EOF )
+		{
+			if( errno == EINTR )
+			{
+				/* Wait for signal handler to end */
+				continue;
+			}
+			else
+			{
+				puts("Error while reading input from stdin");
+				fclose(log1);
+				fclose(log2);
+				exit(1);
+			}
+		}
+
 		/* Ignore newlines and spaces */
 		if( c == '\n' || c == 32 )
 		{
@@ -170,25 +202,25 @@ main(int argc, char * argv[])
 		
 		if( c == 'q' )
 		{
-            /* Exit program */
+			/* Exit program */
 			break;
 		}
 		else if( c != 'f' )
 		{
-            /* Write character to pipe for child processes */
-			if( write(pipe_id[1], &c, 1) != 1 )
+			/* Write character to pipe for child processes */
+			if( write(pipe_id[1], &c, 1) <= 0 )
 			{
 				perror("Cannot write to pipe \n");
 				exit(1);
 			}
-               
-            /* Wait for child process to 'eat the poison' */
-			if( c == 'P' )
-                wait(NULL);
+			   
+			/* Wait for child process to 'eat the poison' */
+			//if( c == 'P' )
+			//	wait(NULL);
 		}
 		else
 		{
-            pid_t child_id;
+			pid_t child_id;
 			
 			kiddoCount++;
 			
@@ -198,24 +230,26 @@ main(int argc, char * argv[])
 			switch( (child_id = fork()) )
 			{
 				case -1:
-                    /* An error occured while forking */
+					/* An error occured while forking */
 					perror("Child could not be created \n");
 					exit(1);
 				case 0:
-                    /* Child process after fork: read from pipe */
+					/* Child process after fork: Start reading from pipe */
 					gup(log1, log2, pipe_id, kiddoCount);
 					break;
 				default:
-                    /* Parent proces after fork: Print child's process id */
+					/* Parent proces after fork: Print child's process id */
 					fprintf(log1, "Started child process %d with id %d \n",
-                            kiddoCount, child_id);
+					        kiddoCount, child_id);
 					fprintf(log2, "Started child process %d with id %d \n",
-                            kiddoCount, child_id);
+					        kiddoCount, child_id);
+					printf("Started child process %d with id %d \n",
+					       kiddoCount, child_id);
 			}
 		}
 	}
-    
-    /* Close logs and exit normally */
+	
+	/* Close logs and exit normally */
 	fprintf(log1, "Program exited normally \n");
 	fprintf(log2, "Program exited normally \n");
 	fclose(log1);