unix.c

/*  $Id$

    Part of SWI-Prolog

    Author:        Jan Wielemaker
    E-mail:        jan@swi.psy.uva.nl
    WWW:           http://www.swi-prolog.org
    Copyright (C): 1985-2002, University of Amsterdam

    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    This library is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with this library; if not, write to the Free Software
    Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
*/

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <SWI-Stream.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <assert.h>
#include "clib.h"
#include <signal.h>
#include <string.h>
#include <errno.h>
#ifdef HAVE_ALLOCA_H
#include <alloca.h>
#endif
#ifdef HAVE_CRT_EXTERNS_H
#include <crt_externs.h>
#endif

install_t
install_unix(void);

/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Unix process management.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */

static IOSTREAM *
name_to_stream(const char *name)
{ IOSTREAM *s;
  term_t t = PL_new_term_ref();

  PL_put_atom_chars(t, name);
  if ( PL_get_stream_handle(t, &s) )
    return s;

  return NULL;
}


static void
flush_stream(const char *name)
{ IOSTREAM *s;

  if ( (s = name_to_stream(name)) )
    Sflush(s);

  PL_release_stream(s);
}



static foreign_t
pl_fork(term_t a0)
{ pid_t pid;

  flush_stream("user_output");		/* general call to flush all IO? */

  if ( (pid = fork()) < 0 )
    return PL_resource_error("memory");

  if ( pid > 0 )
  { return PL_unify_integer(a0, pid);
  } else
  { PL_set_prolog_flag("pid", PL_INTEGER, (intptr_t)getpid());

    return PL_unify_atom_chars(a0, "child");
  }
}


#define free_argv(n) \
	{ int _k; \
	  for( _k=1; _k <= n; _k++) \
	    free(argv[_k]); \
	  free(argv); \
	}

static foreign_t
pl_exec(term_t cmd)
{ int argc;
  atom_t name;

  if ( PL_get_name_arity(cmd, &name, &argc) )
  { term_t a = PL_new_term_ref();
    char **argv = malloc(sizeof(char*) * (argc + 2));
    int i;

    argv[0] = (char *)PL_atom_chars(name);

    for(i=1; i<=argc; i++)
    { char *s;

      if ( PL_get_arg(i, cmd, a) &&
	   PL_get_chars(a, &s, CVT_ALL|REP_MB|BUF_MALLOC) )
	argv[i] = s;
      else
      { free_argv(i-1);
	return pl_error("exec", 1, NULL, ERR_ARGTYPE, i, a, "atomic");
      }
    }
    argv[argc+1] = NULL;

    execvp(argv[0], argv);
    free_argv(argc);
    return pl_error("exec", 1, NULL, ERR_ERRNO, errno, "execute", "command", cmd);
  }

  return pl_error("exec", 1, NULL, ERR_ARGTYPE, 1, cmd, "compound");
}


static foreign_t
pl_wait(term_t Pid, term_t Status)
{ int status;
  pid_t pid = -1;
  int pid_i;

  if ( PL_is_variable(Pid) )
  { pid = -1;
  } else if ( PL_get_integer_ex(Pid, &pid_i) )
  { if ( pid_i <= 0 )
      return PL_domain_error("process_id", Pid);
    pid = pid_i;
  } else
    return FALSE;

  for(;;)
  { pid = waitpid(pid, &status, 0);
    if ( pid == -1 && errno == EINTR )
    { if ( PL_handle_signals() < 0 )
	return FALSE;
    } else
    { break;
    }
  }

  if ( pid == -1 )
    return pl_error("wait", 2, NULL, ERR_ERRNO, errno, "wait", "process", Pid);

  if ( PL_unify_integer(Pid, pid) )
  { if ( WIFEXITED(status) )
      return PL_unify_term(Status,
			   CompoundArg("exited", 1),
			   IntArg(WEXITSTATUS(status)));
    if ( WIFSIGNALED(status) )
      return PL_unify_term(Status,
			   CompoundArg("signaled", 1),
			   IntArg(WTERMSIG(status)));
    if ( WIFSTOPPED(status) )
      return PL_unify_term(Status,
			   CompoundArg("stopped", 1),
			   IntArg(WSTOPSIG(status)));
    assert(0);
  }

  return FALSE;
}


static foreign_t
pl_kill(term_t Pid, term_t Sig)
{ int pid;
  int sig;

  if ( !PL_get_integer(Pid, &pid) )
    return pl_error("kill", 2, NULL, ERR_ARGTYPE, 1, Pid, "pid");
  if ( !PL_get_signum_ex(Sig, &sig) )
    return FALSE;

  if ( kill(pid, sig) < 0 )
    return pl_error("kill", 2, NULL, ERR_ERRNO, errno,
		    "kill", "process", Pid);

  return TRUE;
}


		 /*******************************
		 *	   STREAM STUFF		*
		 *******************************/

static foreign_t
pl_pipe(term_t Read, term_t Write)
{ int fd[2];
  IOSTREAM *in, *out;

  if ( pipe(fd) != 0 )
    return pl_error("pipe", 2, NULL, ERR_ERRNO, errno, "create", "pipe", 0);

  in  = Sfdopen(fd[0], "r");
  out = Sfdopen(fd[1], "w");

  if ( PL_open_stream(Read, in) &&
       PL_open_stream(Write, out) )
    return TRUE;

  return FALSE;
}


static int
get_stream_no(term_t t, IOSTREAM **s, int *fn)
{ if ( PL_get_integer(t, fn) )
    return TRUE;
  if ( PL_get_stream_handle(t, s) )
  { *fn = Sfileno(*s);
    return TRUE;
  }

  return FALSE;
}


static foreign_t
pl_dup(term_t from, term_t to)
{ IOSTREAM *f = NULL, *t = NULL;
  int rval = FALSE;
  int fn, tn;

  if ( !get_stream_no(from, &f, &fn) ||
       !get_stream_no(to, &t, &tn) )
    goto out;

  if ( dup2(fn, tn) < 0 )
  { pl_error("dup", 2, NULL, ERR_ERRNO, errno, "dup", "stream", from);
    goto out;
  } else
  { rval = TRUE;
  }

out:
  if ( f )
    PL_release_stream(f);
  if ( t )
    PL_release_stream(t);

  return rval;
}


static foreign_t
pl_environ(term_t l)
{
#ifdef HAVE__NSGETENVIRON
  char **environ = *_NSGetEnviron();
#else
  extern char **environ;
#endif
  char **e;
  term_t t = PL_copy_term_ref(l);
  term_t t2 = PL_new_term_ref();
  term_t nt = PL_new_term_ref();
  term_t vt = PL_new_term_ref();
  functor_t FUNCTOR_equal2 = PL_new_functor(PL_new_atom("="), 2);

  for(e = environ; *e; e++)
  { char *s = strchr(*e, '=');

    if ( !s )
      s = *e + strlen(*e);

    { int len = s-*e;
      char *name = alloca(len+1);

      strncpy(name, *e, len);
      name[len] = '\0';
      PL_put_atom_chars(nt, name);
      PL_put_atom_chars(vt, s+1);
      if ( !PL_cons_functor(nt, FUNCTOR_equal2, nt, vt) ||
	   !PL_unify_list(t, t2, t) ||
	   !PL_unify(t2, nt) )
	return FALSE;
    }
  }

  return PL_unify_nil(t);
}


		 /*******************************
		 *	    DEAMON IO		*
		 *******************************/

static IOSTREAM *log_stream = NULL;		/* Write log output here */

static ssize_t
read_eof(void *handle, char *buf, size_t count)
{ return 0;
}


static ssize_t
write_null(void *handle, char *buf, size_t count)
{ if ( log_stream )
  { Slock(log_stream);
    Sfwrite(buf, count, sizeof(char), log_stream);
    Sunlock(log_stream);
  }

  return count;
}


static long
seek_error(void *handle, long pos, int whence)
{ return -1;
}


static int
close_null(void *handle)
{ return 0;
}


static IOFUNCTIONS dummy =
{ read_eof,
  write_null,
  seek_error,
  close_null,
  NULL
};


static void
close_underlying_fd(IOSTREAM *s)
{ if ( s )
  { int fd;

    if ( (fd = Sfileno(s)) >= 0 && (s->flags & SIO_ISATTY) )
    { close(fd);

      s->functions = &dummy;
      s->flags &= ~SIO_FILE|SIO_ISATTY;	/* no longer a file */
      s->flags |= SIO_LBUF;		/* do line-buffering */
    }
  }
}


static void
detach_process(void)
{
#ifdef HAVE_SETSID
  setsid();
#else
  int fd;

  if ( (fd = open("/dev/tty", 2)) )
  { ioctl(fd, TIOCNOTTY, NULL);		/* detach from controlling tty */
    close(fd);
  }
#endif
}

static foreign_t
pl_detach_IO(term_t stream)
{ if ( !log_stream )
  { IOSTREAM *s;

    if ( !PL_get_stream_handle(stream, &s) )
      return FALSE;
    log_stream = s;
    PL_release_stream(s);

    close_underlying_fd(Serror);
    close_underlying_fd(Soutput);
    close_underlying_fd(Sinput);

    detach_process();
  }

  return TRUE;
}


install_t
install_unix(void)
{ PL_register_foreign("fork_",     1, pl_fork, 0);
  PL_register_foreign("exec",      1, pl_exec, 0);
  PL_register_foreign("wait",      2, pl_wait, 0);
  PL_register_foreign("kill",      2, pl_kill, 0);
  PL_register_foreign("pipe",      2, pl_pipe, 0);
  PL_register_foreign("dup",       2, pl_dup, 0);
  PL_register_foreign("detach_IO", 1, pl_detach_IO, 0);
  PL_register_foreign("environ",   1, pl_environ, 0);
}