ex1,2 w6

#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>

void sigusr1_handler(int signum) {
    // Read and print the contents of text.txt
    char buffer[1024];
    int file_descriptor = open("text.txt", O_RDONLY);
    ssize_t bytes_read;
    while ((bytes_read = read(file_descriptor, buffer, sizeof(buffer))) > 0) {
        write(STDOUT_FILENO, buffer, bytes_read);
    }
    close(file_descriptor);
}

void sigusr2_handler(int signum) {
    // Print a termination message and exit
    printf("Process terminating...\n");
    exit(0);
}

void sigterm_handler(int signum) {
    // Print a termination message and exit
    printf("Process terminating...\n");
    exit(0);
}

int main() {
    // Create the agent.pid file and write the PID into it
    FILE* pid_file = fopen("/var/run/agent.pid", "w");
    if (pid_file == NULL) {
        perror("Error creating agent.pid file");
        exit(1);
    }
    fprintf(pid_file, "%d", getpid());
    fclose(pid_file);

    // Register signal handlers for SIGUSR1, SIGUSR2, and SIGTERM
    signal(SIGUSR1, sigusr1_handler);
    signal(SIGUSR2, sigusr2_handler);
    signal(SIGTERM, sigterm_handler);

    // Read and print the initial contents of text.txt
    char buffer[1024];
    int file_descriptor = open("text.txt", O_RDONLY);
    ssize_t bytes_read;
    while ((bytes_read = read(file_descriptor, buffer, sizeof(buffer))) > 0) {
        write(STDOUT_FILENO, buffer, bytes_read);
    }
    close(file_descriptor);

    // Sleep indefinitely
    while (1) {
        sleep(3600);  // Sleep for a long time (1 hour)
    }

    return 0;
}


#include <stdio.h>
#include <stdlib.h>
#include <signal.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/stat.h>

int agent_pid;

void sigint_handler(int signum) {
    // Send SIGTERM to the agent and exit
    if (agent_pid > 0) {
        kill(agent_pid, SIGTERM);
    }
    exit(0);
}

int main() {
    // Check if the agent.pid file exists
    struct stat stat_buffer;
    if (stat("/var/run/agent.pid", &stat_buffer) == -1) {
        perror("Error: No agent found.");
        exit(1);
    }

    // Try to open the agent.pid file to get the agent's PID
    FILE* pid_file = fopen("/var/run/agent.pid", "r");
    if (pid_file == NULL) {
        perror("Error reading agent PID.");
        exit(1);
    }
    fscanf(pid_file, "%d", &agent_pid);
    fclose(pid_file);

    printf("Agent found.\n");

    // Register the Ctrl+C signal handler
    signal(SIGINT, sigint_handler);

    while (1) {
        printf("Choose a command {\"read\", \"exit\", \"stop\", \"continue\"}: ");
        char command[20];
        scanf("%s", command);

        if (strcmp(command, "read") == 0) {
            // Send SIGUSR1 to the agent
            kill(agent_pid, SIGUSR1);
        } else if (strcmp(command, "exit") == 0) {
            // Send SIGUSR2 to the agent and exit
            kill(agent_pid, SIGUSR2);
            exit(0);
        } else if (strcmp(command, "stop") == 0) {
            // Send SIGSTOP to the agent
            kill(agent_pid, SIGSTOP);
        } else if (strcmp(command, "continue") == 0) {
            // Send SIGCONT to the agent
            kill(agent_pid, SIGCONT);
        } else {
            printf("Invalid command.\n");
        }
    }

    return 0;
}