Aim :

Write a C/C++ program to set up a real-time clock interval timer using the alarm API.

Theory :

• First, every signal has a name. These names all begin with the three characters SIG .For example,SIGABRT is the abort signal that is generated when a process calls the abort function.
• SIGALRM is the alarm signal that is generated when the timer set by the alarm function goes off.
• Use the alarm API for generating a signal after certain time interval as specified by the user.

Code :

 #include<stdio.h>
 #include<stdlib.h>
 #include<unistd.h>
 #include<signal.h>
 #define INTERVAL 5
 void callme(int sig_no)
 {
    alarm(INTERVAL);
    printf("Hello!!\n");
 }
 int main()
 {
    struct sigaction action;
    action.sa_handler=(void(*)(int))callme;
    sigaction(SIGALRM,&action,0);
    alarm(2);
    sleep(5);
    return 0;
 }

Output :

1. Open a terminal.
2. Change directory to the file location in both the terminals.
3. Open a file using command followed by program_name

   vi 10_alarm_signal_handler.cpp 

   and then enter the source code and save it.
4. Then compile the program using

   g++ 10_alarm_signal_handler.cpp

5. If there are no errors after compilation execute the program using

   ./a.out

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