shellpipe.c

 /* simple shell, parses batches of commands separated by pipes and executes them in separate processes */
 /* useful characters: [] # */

 # include <stdio.h>
 # include <string.h>
 # include <fcntl.h> // for O_RDONLY
 # include <stdlib.h> // for exit()
 # include <unistd.h> // for execlp()

 # define errormsg(x) { puts(x); exit(1); }
 # define SIZE 1024

 int main(int argc, char * argv[])
    {
     char *cmd[SIZE]; // stores the current command
     int index = 0; // read index
     int quit = 0;
     int processes = 0; // active processes
     int status; // child or parent process
     char c;
     printf("Type command: ");
     while(!quit && c != EOF)
    {
     index++;
     c = getchar();
     if(c != '\0' && c != '|')
        cmd[index] = c;
     if(c == '|') // executes command and empties buffer
        {
         int pid = fork();
         processes++; // process added
         if(pid != 0) wait(&status);
         execlp(cmd, cmd, 0);
         cmd = ""; // COMPILATION ERROR here
        }
     if(strcmp(cmd, "quit\n") == 0) quit = 1;
    }
     printf("Batch executed\n");
     int i;
     for(i = 0; i < processes; i++) // waits until all processes have terminated
    wait(&status);
    }