dpipe.c

/* Copyright 2003 Renzo Davoli
 * Licensed under the GPL
 */

#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>

static char *progname;
static int alternate_stdin;
static int alternate_stdout;


void usage() {
  fprintf(stderr, "Usage:\n\t%s cmd1 [arg1...] = cmd2 [arg2...]\n\n", progname);
  kill(getpgrp(), SIGTERM);
  exit(-1);
}


int splitindex(int argc, char *argv[], int *dirchar) {
  register int i;

  for (i = 0; i < argc; i++) {
    if (*dirchar == argv[i][0] && argv[i][1] == '=') {
      (argv[i])++;
      *dirchar = 0;
    }
    if (argv[i][0] == '=') {
      if (argv[i][1] == '}' || argv[i][1] == '{')
        *dirchar = argv[i][1];
      break;
    }
  }
  return i;
}


static void alternate_fd() {
  char numstr[10];
  alternate_stdin = open("/dev/null", O_RDONLY);
  alternate_stdout = open("/dev/null", O_RDONLY);
  close(alternate_stdin);
  close(alternate_stdout);
  snprintf(numstr, 10, "%d", alternate_stdin);
  setenv("ALTERNATE_STDIN", numstr, 1);
  snprintf(numstr, 10, "%d", alternate_stdout);
  setenv("ALTERNATE_STDOUT", numstr, 1);
}


int recmain(int argc, char *argv[], int olddirchar) {
  int split;
  int newdirchar = olddirchar;

  split = splitindex(argc, argv, &newdirchar);
  if (split >= argc) {
    if (newdirchar != 0)
      usage();
    execvp(argv[0], argv);
  } else {
    char **argv1, **argv2;
    int p1[2], p2[2];

    if (argc < 3 || split == 0 || split == argc - 1)
      usage();

    pipe(p1);
    if (olddirchar == 0)
      pipe(p2);
    argv[split] = NULL;
    argv1 = argv;
    argv2 = argv + (split + 1);

    if (fork()) {
      switch (olddirchar) {
        case 0:
          close(p1[1]);
          close(p2[0]);
          if (p1[0] != alternate_stdin) {
            dup2(p1[0], alternate_stdin);
            close(p1[0]);
          }
          if (p1[0] != alternate_stdout) {
            dup2(p2[1], alternate_stdout);
            close(p2[1]);
          }
          break;
        case '}':
          close(p1[0]);
          dup2(p1[1], STDOUT_FILENO);
          close(p1[1]);
          break;
        case '{':
          close(p1[1]);
          dup2(p1[0], STDIN_FILENO);
          close(p1[0]);
          break;
        default:
          fprintf(stderr, "CHECA\n");
      }
      execvp(argv1[0], argv1);
    } else {
      switch (olddirchar) {
        case 0:
          close(p2[1]);
          close(p1[0]);
          dup2(p2[0], STDIN_FILENO);
          dup2(p1[1], STDOUT_FILENO);
          close(p2[0]);
          close(p1[1]);
          break;
        case '}':
          close(p1[1]);
          dup2(p1[0], STDIN_FILENO);
          close(p1[0]);
          break;
        case '{':
          close(p1[0]);
          dup2(p1[1], STDOUT_FILENO);
          close(p1[1]);
          break;
        default:
          fprintf(stderr, "CHECA\n");
      }
      recmain(argc - split - 1, argv2, newdirchar);
    }
  }
  return 0;
}


int main(int argc, char *argv[]) {
  int split;
  char **argv1, **argv2;
  int p1[2], p2[2];
  int dirchar = 0;

  progname = argv[0];
  argv++;
  argc--;

  alternate_fd();
  split = splitindex(argc, argv, &dirchar);

  if (argc < 3 || split == 0 || split >= argc - 1)
    usage();

  pipe(p1);
  pipe(p2);
  argv[split] = NULL;
  argv1 = argv;
  argv2 = argv + (split + 1);

  if (fork()) {
    close(p1[1]);
    close(p2[0]);
    dup2(p1[0], STDIN_FILENO);
    dup2(p2[1], STDOUT_FILENO);
    close(p1[0]);
    close(p2[1]);
    execvp(argv1[0], argv1);
  } else {
    close(p2[1]);
    close(p1[0]);
    dup2(p2[0], STDIN_FILENO);
    dup2(p1[1], STDOUT_FILENO);
    close(p1[1]);
    close(p2[0]);
    recmain(argc - split - 1, argv2, dirchar);
  }
  return (0);
}