processesB.c

/* basic operations with processes, part B, 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 CMDLEN 256

 int main(int argc, char * argv[])
    {
     char cmd[CMDLEN];
     int pid, status, cond;
     cond = 1;

     while(cond > 0) // NOTE: THE LOOP DOES NOT BREAK (presumably because of the char, not char*, declaration?)
    {
     printf("Command ('quit' to leave): ");
     scanf("%s", cmd); // memorises the command input by user
     if(strcmp(cmd, "quit") == 0)
        {
         cond = 0;
         break;
        }

     pid = fork(); // forks the current process
     // if(pid == -1) exit(1);
     if(pid == 0) execlp(cmd, cmd, 0); // if current process is child process, replaces it with the cmd
     else wait(&status); // else, waits until first child death
    }
    }