processes.c

 /* basic operations with processes, UNIX-native */

 /* pointer arithmetics:
  *
  * push(pointer, v) INDICATES *(pointer++) = v
  * pop(pointer) INDICATES *(--pointer)
  * (*++v)[0] INDICATES (**++v)
  *           INDICATES first char in v
  *           INDICATES name of string/vector v
  * likewise, *v[0] INDICATES **v
  *       and *v[n] INDICATES **(v + n)
  * returntype (*funct)(args) INDICATES a function funct with arguments args which returns...
  * char **argv INDICATES pointer to char pointer
  * int(*v)[len] INDICATES pointer "v" to a vector of "len" int elements
  * int *v[len] INDICATES vector "v" of "len" pointers to int elements
  * void *funct() INDICATES function "funct" that returns a pointer-to-void
  * void (*funct)() INDICATES pointer to a function "funct" that returns void
  *
  */

 /* useful characters: [] # */

 # include <stdio.h>
 # include <unistd.h> // execlp is defined here

 # define BUFFERSIZE 1024

 int main(int argc, char * argv[])
    {
     /* PID generation and fork() call */
     int pid = fork(); // process ID is now the ID of the current process
     if(pid == 0) printf("{Call 1} Child process, PID = %d\n", pid);
     else printf("{Call 1} Parent process, PID = %d\n", pid);


     /* process status */
     pid = fork();
     int status; // process status
     if(pid == 0) printf("{Call 2} Child process, PID = %d\n", pid);
     else
    {
     wait(&status); // waits until at least one child terminates
     printf("{Call 2} Parent process, PID = %d\n", pid);
    }


    /* exec* calls */
    execlp("ls", "ls", 0);
    printf("execlp(...) not executed");
    }