/* minish.c - example of a minimalistic shell 
 * Comments in code deliberately omitted. :-)
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/wait.h>
#include <signal.h>
#include <setjmp.h>
#include <glob.h>

#define MAXLINE 80

static int cpid = 0;

void inthandler(int sig)
{
  if (cpid) {
    kill(cpid, sig);
    waitpid(cpid, NULL, 0);
    fprintf(stderr, "killed child with pid %d\n", cpid);
    cpid = 0;
  }
  signal(SIGINT, inthandler);
}

int main(int argc, char **argv)
{
  char line[MAXLINE+1], *args[MAXLINE], *p, **arg;
  int bg, tmppid, i;
  glob_t globbuf;
  int globflags;

  if (argc>=2 && !freopen(argv[1], "r", stdin)) {
    perror(argv[1]);
    exit(errno);
  }

  signal(SIGINT, inthandler);

  while (printf("%s","$ "), fgets(line, MAXLINE, stdin)) {
    bg = 0;
    if ((p = strchr(line, '\n'))) {
      *p=0; 
    } else { 
      fprintf(stderr, "line too long\n"); 
      exit(1); 
    }
    p = line;
    while (*p == ' ') 
      ++p;
    if (*p == '#' || !*p) 
      continue;     
    else {
      *(arg=args) = p;           
      while ((p = strchr(p, ' '))) {
	while (*p == ' ') 
	  *p++ = 0;
	if (*p) {
	  if (*p == '&')
	    bg = 1;
	  else
	    *++arg=p;
	}
      }
    }
    *++arg=NULL;

    globflags = GLOB_NOCHECK | GLOB_NOSORT | GLOB_ERR;
    for (i=0; args[i]; i++) {
      glob(args[i], globflags, NULL, &globbuf);
      globflags |= GLOB_APPEND;
    }

    if (!strcmp(line,"exit")) {
      exit(args[1] ? atoi(args[1]) : 0);
    }

    switch ((cpid=fork())) {
    case 0: 
      execvp(args[0], globbuf.gl_pathv);
      perror(args[0]);
      exit(errno);
    case -1: 
      perror("fork() failed");
      break;
    default: 
      if (!bg)
	waitpid(cpid,NULL,0);
      else
	fprintf(stderr,"** Backrounded, pid %d\n", cpid);
      cpid = 0;
      if ((tmppid = waitpid(-1,NULL,WNOHANG)) > 0)
	fprintf(stderr, "** Child with pid %d finished\n", tmppid);
    } 
  }

  exit(0);
}