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

void prep_exe(char *sttp, char **path, char ***argv)
{
  char *p;
  char *endp;
  static int max, i;
  for (p = sttp; *p != '\0'; p++)
    ;
  endp = p;
  i = 0;
  for (p = sttp; p < endp; p++) {
    if (*p == ' ') {
      *p = '\0';
      p++;
      i++;
      for (;*p == ' '; p++)
        ;
    }
  }
  max = i + 2;
  *argv = malloc(sizeof(char *) * max);
  *path = sttp;
  (*argv)[0] = sttp;
  i = 1;
  for (p = sttp; p < endp; p++) {
    if (*p == '\0') {
      p++;
      for (;*p == ' '; p++)
        ;
      (*argv)[i++] = p;
    }
  }
  (*argv)[i] = NULL;
  return;
}

char *cut(char *comline, char *last)
{
  char *p;
  for (p = last; *p != '|' && p > comline; p--)
    ;
  if (p > comline) {
    *p = '\0';
    return p + 1;
  } else {
    return p;
  }
}

void task(char *comline)
{
  char *endpos, *p, *path, **argv;
  int pid, status;
  int fd[2];
  for (p = comline; *p != '\0'; p++)
    ;
  p = cut(comline, p);
  endpos = p;
  if (fork() == 0) {
    for (;;) {
      if (p < endpos) {
        dup2(fd[1], 1);
        close(fd[1]);
        close(fd[0]);
      }
      if (p > comline) {
        pipe(fd);
        if ((pid = fork()) == 0) {
          p = cut(comline, p);
          continue;
        } else {
          dup2(fd[0], 0);
          close(fd[0]);
          close(fd[1]);
          prep_exe(p, &path, &argv);
          execv(path, argv);
          /* not reached if no error */
          fprintf(stderr, "cannot found %s\n", path);
          free(*argv);
          exit(-1);
        }
      } else {
        prep_exe(p, &path, &argv);
        execv(path, argv);
        /* not reached if no error */
        fprintf(stderr, "cannot found %s\n", path);
        free(*argv);
        exit(-1);
      }
    } /* for (;;) */
  } else {
    wait(&status);
    putchar('\n');
  }
}
#define BUFFSIZE 1024 /* >= 2 */
char *mygetline(FILE *fp)
{
  static char inbuff[BUFFSIZE];
  char *outbuff_malloc, *tmpbuff;
  char *p, *q;
  int fEOL;
  if ((outbuff_malloc = malloc(1)) == NULL) {
    return NULL;
  }
  *outbuff_malloc = '\0';
  fEOL = 0;
  do {
    if ((q = fgets(inbuff, BUFFSIZE, fp)) == NULL)
      break;
    for (p = inbuff; *p != '\0'; p++)
      ;
    if (*(p - 1) == '\n') {
      *(p - 1) = '\0';
      fEOL = 1;
    }
    if ((tmpbuff = realloc(outbuff_malloc, strlen(outbuff_malloc) + strlen(inbuff) + 1)) ==NULL) {
      free(outbuff_malloc);
      return NULL;
    }
    strcat(tmpbuff, inbuff);
    outbuff_malloc = tmpbuff;
  } while (!fEOL);
  if (q == NULL) {
    free(outbuff_malloc);
    return NULL;
  }
  return outbuff_malloc;
}

int main()
{
  char *inputLine_malloc;

  for (;;) {
    printf("> ");
    if ((inputLine_malloc = mygetline(stdin)) == NULL) {
      break;
    }
    if (strstr(inputLine_malloc, "exit") != NULL) {
      free(inputLine_malloc);
      break;
    } else {
      task(inputLine_malloc);
      free(inputLine_malloc); /* NULL ok */
    }
  }
  return 0;
}
/* end */

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