shell.c

#include <stdio.h>
#include <stdlib.h>
#include <readline/readline.h>
#include <readline/history.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <assert.h>

#define MAXARGS 100
#define PIPE_READ 0
#define PIPE_WRITE 1

typedef struct command {
    char *cmd;
    int argc;
    char *argv[MAXARGS+1];
    struct command *next;
} COMMAND;

char* inputfile = NULL;
char* outputfile = NULL;
int background_exec = 0;

COMMAND* parse(char* linha);
void print_parse(COMMAND* commlist);
void execute_commands(COMMAND* commlist);
void free_commlist(COMMAND* commlist);

#include "parser.c"

int main(int argc, char* argv[]) {
  char *linha;
  COMMAND *com;

  while (1) {
    if ((linha = readline("my_prompt$ ")) == NULL)
      exit(0);
    if (strlen(linha) != 0) {
      add_history(linha);
      com = parse(linha);
      if (com) {
	print_parse(com);
	execute_commands(com);
	free_commlist(com);
      }
    }
    free(linha);
  }
}


void print_parse(COMMAND* commlist) {
  int n, i;

  printf("---------------------------------------------------------\n");
  printf("BG: %d IN: %s OUT: %s\n", background_exec, inputfile, outputfile);
  n = 1;
  while (commlist != NULL) {
    printf("#%d: cmd '%s' argc '%d' argv[] '", n, commlist->cmd, commlist->argc);
    i = 0;
    while (commlist->argv[i] != NULL) {
      printf("%s,", commlist->argv[i]);
      i++;
    }
    printf("%s'\n", commlist->argv[i]);
    commlist = commlist->next;
    n++;
  }
  printf("---------------------------------------------------------\n");
}

void free_commlist(COMMAND *commlist){
}

void execute_commands(COMMAND *commlist) {
  int fd[2];
  pid_t pid;
  int n_pipes=2; //pipes needed
  COMMAND *aux = commlist;

  int i;
  for(i=0;i<n_pipes; i++){
    int oldfd = 0;

    if(fd[0]!=0){
      close(fd[1]);
      oldfd = fd[0];
    }
      pipe(fd);

      if((pid=fork())<0){perror("Fork Failed");}
      else
        if(pid == 0){

          if(inputfile!=NULL){
            int in = open(inputfile,O_RDONLY);
            dup2(in,STDIN_FILENO);
            inputfile = NULL;
          }

          if(outputfile != NULL){
            int out = open(outputfile, O_RDWR |O_CREAT | O_TRUNC, S_IRWXU);
            dup2(out,STDOUT_FILENO);
            outputfile = NULL;
          }

          if(oldfd)
            dup2(oldfd,STDIN_FILENO);

          if(commlist->cmd == "grepwc"){
            if(i==0){
              if(execlp("grep","grep","celio",NULL)<0){
                perror("Bad command");
                exit(1);
              }
            }

            if(i==1){
              if(execlp("wc","wc","-l",NULL) < 0){
                perror("Bad command");
                exit(1);
              }
            }
          }
        }//child
  }
}