exec_cmd.c

/*
** exec_cmd.c for 42sh in /home/seblu/devel/c/42sh/src/execution
**
** Made by Seblu
** Login   <seblu@epita.fr>
**
** Started on  Sat Apr  8 07:38:48 2006 Seblu
** Last update Sun May 21 17:07:27 2006 Seblu
*/

#define DEBUG_EXEC 0

#include <unistd.h>
#include <assert.h>
#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <fcntl.h>
#include "../main/42sh.h"
#include "../ast/ast.h"
#include "execution.h"
#include "../builtin/builtin.h"
#include "../var/var.h"
#include "../globbing/quoting.h"
#include "../history/history.h"
#include "../expand/expand.h"

#include "mem.h"

#define rederror(prompt) do { perror(prompt); return 0; } while (0)

struct			s_reds_context
{
  int			old;
  int			save;
  int			end;
};

static void		create_fork(struct s_cmd *cmd, struct s_42sh *sh);
static void		launch_cmd(struct s_cmd *cmd);
static int		apply_reds(struct s_redir **reds);
static void		parse_prefix(char **prefix, int glob, struct s_42sh *s);
static struct s_reds_context	*save_reds_context(struct s_redir **reds);
static void		restore_reds_context(struct s_reds_context *context);
static int		get_filedes(const char *txt);
static void		cmd_debugger(struct s_cmd *cmd);

/*!
** Execute a command node
**
** @param cmd cmd to execute
** @param sh sh params
*/
void			exec_cmd(struct s_cmd *cmd, struct s_42sh *sh)
{
  struct s_reds_context	*context;

  assert(cmd && sh);
  if (DEBUG_EXEC)
     cmd_debugger(cmd);
  word_expansion(&cmd->argv, sh);
  if (!cmd->argv)
  {
     parse_prefix(cmd->assign_words, 0, sh);
     return;
  }
  if (is_a_builtin(cmd->argv[0], sh))
  {
     context = save_reds_context(cmd->redirs);
     if (!apply_reds(cmd->redirs))
	sh->last_status = RED_ERROR;
     else
	sh->last_status = exec_builtin(cmd, sh);
     restore_reds_context(context);
     free(context);
  }
  else
     create_fork(cmd, sh);
}

/*!
** Execute a command in a pipeline. This call preserve for too many system call fork
** Take care, this must be called after a fork
**
** @param cmd cmd to execute
** @param sh sh structure
*/
void			exec_piped_cmd(struct s_cmd *cmd, struct s_42sh *sh)
{
  assert(cmd && sh);
  if (DEBUG_EXEC)
     cmd_debugger(cmd);
  word_expansion(&cmd->argv, sh);
  if (!apply_reds(cmd->redirs))
     exit(RED_ERROR);
  if (is_a_builtin(cmd->argv[0], sh))
    sh->last_status = exec_builtin(cmd, sh);
  else
  {
    parse_prefix(cmd->assign_words, 1, sh);
    launch_cmd(cmd);
  }
}

/*!
** Set redirection for builtin
**
** @param reds redirection informations
**
** @return save of all fd permutations
*/
static struct s_reds_context	*save_reds_context(struct s_redir **reds)
{
  struct s_reds_context		*context;
  register int			i;

  for (i = 0; reds[i]; ++i)
    ;
  secmalloc(context, (i + 1) * sizeof (struct s_reds_context));
  for (i = 0; reds[i]; ++i)
  {
    context[i].old = reds[i]->fd;
    context[i].save = dup(reds[i]->fd);
    context[i].end = 0;
  }
  context[i].end = 1;
  return context;
}

static void		restore_reds_context(struct s_reds_context *context)
{
  register int		i;

  for (i = 0; !context[i].end; ++i)
     dup2(context[i].save, context[i].old);
}

/*!
** Manage fork enterpise for a command
**
** @param cmd command to execute
** @param sh shell struct
*/
static void		create_fork(struct s_cmd *cmd, struct s_42sh *sh)
{
   pid_t		pid;
   int			status;

  if ((pid = fork()) == -1)
  {
     fprintf(stderr, "42sh: Cannot fork\n");
     sh->last_status = FORK_ERROR;
     return;
  }
  if (pid)
  {
     waitpid(pid, &status, 0);
     sh->last_status = WEXITSTATUS(status);
  }
  else
  {
     parse_prefix(cmd->assign_words, 1, sh);
     if (!apply_reds(cmd->redirs))
	exit(RED_ERROR);
     launch_cmd(cmd);
  }
}

/*!
** Certify a correct changement of context
**
** @param cmd Execute a command
*/
static void		launch_cmd(struct s_cmd *cmd)
{
  execvp(cmd->argv[0], cmd->argv);
  if (errno == ENOENT)
    if (strchr(cmd->argv[0], '/') == NULL)
      fprintf(stderr, "42sh: %s: command not found\n", cmd->argv[0]);
    else
      fprintf(stderr, "42sh: %s: No such file or directory\n", cmd->argv[0]);
  else
    perror("42sh");
  exit((errno == ENOENT) ? 127 : 126);
}

/*!
** Parse prefix of command, and set variable local or global.
**
** @param prefix assignment words list
** @param glob variable set is global only or local
** @param sh shell info
*/
static void		parse_prefix(char **prefix, int glob, struct s_42sh *sh)
{
  register int		i;
  char			*value;

  if (!prefix)
     return;
  for (i = 0; prefix[i];  ++i)
  {
     if (!(value = strchr(prefix[i], '=')))
	assert(0);
     *value++ = 0;
     if (glob)
	var_setenv(prefix[i], value, !0);
     else
	var_set(sh->vars, prefix[i], value, !0);
  }
}

/*!
** Apply redirections whitout save of file descriptors
**
** @param reds list of redirections
*/
static int		apply_reds(struct s_redir **reds)
{
   int			fd;
   int			i;
   char			*filename;

   assert(reds);
   for (i = 0; reds[i]; ++i)
   {
      switch (reds[i]->type)
      {
	 case R_LESS:
	    if ((fd = open(reds[i]->file, O_RDONLY)) == -1)
	       rederror("42sh");
	    dup2(fd, reds[i]->fd);
	    break;
	 case R_DLESSDASH:
	 case R_DLESS:
	    if ((fd = mkstemp(filename = strdup("42sh.heredocs.XXXXXX"))) == -1)
	       rederror("42sh");
	    write(fd, reds[i]->file, strlen(reds[i]->file));
	    lseek(fd, 0, SEEK_SET);
	    unlink(filename);
	    free(filename);
	    dup2(fd, STDIN_FILENO);
	    close(fd);
	    break;
	 case R_GREAT:
	 case R_CLOBBER:
	    if ((fd = open(reds[i]->file, O_WRONLY | O_CREAT | O_TRUNC, 0666)) == -1)
	       rederror("42sh");
	    dup2(fd, reds[i]->fd);
	    break;
	 case R_DGREAT:
	    if ((fd = open(reds[i]->file, O_WRONLY | O_CREAT | O_APPEND, 0666)) == -1)
	       rederror("42sh");
	    dup2(fd, reds[i]->fd);
	    break;
	 case R_GREATAND:
	 case R_LESSAND:
	    if ((fd = get_filedes(reds[i]->file)) == -1)
	       return 0;
	    if (fd == -2)
	       close(reds[i]->fd);
	    else
	       dup2(fd, reds[i]->fd);
	    break;
	 default:
	    return 0;
      }
   }
   return 1;
}

/*!
** Retrieve an fd from and redirect words
**
** @param txt fd in string
**
** @return -1 if fail, -2 for close fd else fd
*/
static int		get_filedes(const char *txt)
{
   long			fd;
   char			*endbuf;

   assert(txt);
   if (txt[0] == '-' && txt[1] == 0)
      return -2;
   fd = strtol(txt, &endbuf, 10);
   if (endbuf == txt || *endbuf != 0)
   {
      fprintf(stderr, "42sh: %s: ambiguous redirect\n", txt);
      return -1;
   }
   if (-1 == fcntl(fd, F_GETFL))
   {
      endbuf = strmerges(2, "42sh: ", txt);
      perror(endbuf);
      free(endbuf);
      return -1;
   }
   return 0;
}

/*!
** Debug execution
**
** @param cmd command
*/
static void		cmd_debugger(struct s_cmd *cmd)
{
   int			i;

   fprintf(stderr, "-----------------------------------\n");
   fprintf(stderr, "exec command\n");
   for (i = 0; cmd->argv && cmd->argv[i]; ++i)
      fprintf(stderr, "argv[%d]   : %-15s\n", i, cmd->argv[i]);
   for (i = 0; cmd->assign_words && cmd->assign_words[i]; ++i)
      fprintf(stderr, "prefix[%d] : %-15s\n", i, cmd->assign_words[i]);
   for (i = 0; cmd->redirs && cmd->redirs[i]; ++i)
   {
      fprintf(stderr, "reds[%d]   : type : %d\n", i, cmd->redirs[i]->type);
      fprintf(stderr, "            : fd   : %d\n", cmd->redirs[i]->fd);
      fprintf(stderr, "            : file : %s\n", cmd->redirs[i]->file);
   }
   fprintf(stderr, "-----------------------------------\n");
}