some practices added

CSE344 - System Programming/Coding Practices/practice13.c

@@ -0,0 +1,44 @@
+// Create a process and kill it by using kill() system call.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <signal.h>
+
+int main(int argc, char *argv[])
+{
+ pid_t pid;
+ int status;
+
+ // kill(getpid(), SIGKILL); // kills itself
+
+ // parent process created first, then child process
+ // after 5 second delay, parent process being killed
+ // so the child process never gets a chance to terminate
+
+ pid = fork();
+ if (pid == 0)
+ {
+ printf("Child process is created. PID: %d\n", getpid());
+ sleep(10);
+ printf("Child process is terminated.\n");
+ }
+ else if (pid > 0)
+ {
+ printf("Parent process is created. PID: %d\n", getpid());
+ sleep(5);
+ kill(pid, SIGKILL);
+ wait(&status);
+ printf("Parent process is terminated.\n");
+ // print pid
+ }
+ else
+ {
+ perror("fork");
+ exit(1);
+ }
+
+ return 0;
+}

CSE344 - System Programming/Coding Practices/practice14.c

@@ -0,0 +1,29 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+
+void sigint_handler(int sig)
+{
+ printf("Received SIGINT signal.\n");
+ if (signal(SIGINT, SIG_DFL) == SIG_ERR)
+ {
+ printf("Error setting signal handler for SIGINT.\n");
+ exit(1);
+ }
+}
+
+int main()
+{
+ // Install the signal handler for SIGINT
+ signal(SIGINT, sigint_handler);
+
+ printf("Press Ctrl+C to send a SIGINT signal.\n");
+
+ // Loop forever
+ while (1)
+ {
+ // Do some work
+ }
+ return 0;
+}

CSE344 - System Programming/Coding Practices/practice15.c

@@ -0,0 +1,58 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+
+// First signals will be handled by the signal handlers
+// after that, the default signal handlers will be called
+
+void sigint_handler(int sig)
+{
+ printf("Received SIGINT signal.\n");
+ if (signal(SIGINT, SIG_DFL) == SIG_ERR)
+ {
+ printf("Error setting signal handler for SIGINT.\n");
+ exit(1);
+ }
+}
+
+void sigterm_handler(int sig)
+{
+ printf("Received SIGTERM signal.\n");
+ if (signal(SIGTERM, SIG_DFL) == SIG_ERR)
+ {
+ printf("Error setting signal handler for SIGTERM.\n");
+ exit(1);
+ }
+}
+
+void sigkill_handler(int sig)
+{
+ // Handling SIGKILL is not possible, so this function will never be called
+ printf("Received SIGKILL signal.\n");
+ if (signal(SIGKILL, SIG_DFL) == SIG_ERR)
+ {
+ printf("Error setting signal handler for SIGKILL.\n");
+ exit(1);
+ }
+}
+
+int main()
+{
+ // Install the signal handlers
+ signal(SIGINT, sigint_handler);
+ signal(SIGTERM, sigterm_handler);
+ signal(SIGKILL, sigkill_handler); // SIGKILL cannot be caught or ignored
+
+ printf("Press Ctrl+C to send a SIGINT signal.\n");
+ printf("To kill this process by SIGTERM, use the following command: kill -SIGTERM %d\n", getpid());
+ printf("To kill this process by SIGKILL, use the following command: kill -9 %d\n", getpid());
+
+ // Loop forever
+ while (1)
+ {
+ // Do some work
+ }
+
+ return 0;
+}

CSE344 - System Programming/Coding Practices/practice16.c

@@ -0,0 +1,45 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <unistd.h>
+
+void critical_operation()
+{
+ printf("Performing critical operation... ('enter' to continue)\n");
+ // Do some work
+ while (1)
+ {
+ if (getchar() == '\n')
+ {
+ break;
+ }
+ }
+ printf("Critical operation complete.\n");
+}
+
+int main()
+{
+ sigset_t mask; // create a signal set
+ sigemptyset(&mask); // initialize the signal set
+ sigaddset(&mask, SIGINT); // add SIGINT to the signal set
+ sigaddset(&mask, SIGTSTP); // add SIGTSTP to the signal set
+ sigprocmask(SIG_BLOCK, &mask, NULL); // block the signals in the signal set
+
+ // Pressing Ctrl+C will not interrupt the program
+ printf("Press Ctrl+C to interrupt the program...\n");
+
+ // Pressing Ctrl+Z will not interrupt the program
+ printf("Press Ctrl+Z to send a SIGTSTP signal...\n");
+
+ // to SIGKILL the program, use the following command: kill -9 <pid> from another terminal
+ printf("To kill this process by SIGKILL, use the following command: kill -9 %d\n", getpid());
+
+ // Perform a critical operation that must not be interrupted
+ critical_operation();
+ // Unblock the SIGINT signal
+ sigprocmask(SIG_UNBLOCK, &mask, NULL);
+
+ printf("Program complete.\n");
+
+ return 0;
+}