mc/src/subshell.c

/* {{{ Copyright notice */

/* Concurrent shell support for the Midnight Commander
   Copyright (C) 1994, 1995 Dugan Porter

   This program is free software; you can redistribute it and/or
   modify it under the terms of Version 2 of the GNU General Public
   License, as published by the Free Software Foundation.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 */

/* }}} */

#include <config.h>
#ifdef HAVE_SUBSHELL_SUPPORT

/* {{{ Declarations */

#ifndef _GNU_SOURCE
#   define _GNU_SOURCE 1
#endif

#include <stdio.h>      
#include <stdlib.h>	/* For errno, putenv, etc.	      */
#include <errno.h>	/* For errno on SunOS systems	      */
#include <termios.h>	/* tcgetattr(), struct termios, etc.  */
#include <sys/types.h>	/* Required by unistd.h below	      */
#ifdef HAVE_SYS_IOCTL_H
#   include <sys/ioctl.h> /* For ioctl() (surprise, surprise) */
#endif
#include <string.h>	/* strstr(), strcpy(), etc.	      */
#include <signal.h>	/* sigaction(), sigprocmask(), etc.   */
#include <sys/stat.h>	/* Required by dir.h & panel.h below  */

#ifdef HAVE_UNISTD_H
#   include <unistd.h>	/* For pipe, fork, setsid, access etc */
#endif

#ifdef HAVE_STROPTS_H
#   include <stropts.h> /* For I_PUSH */
#endif /* HAVE_STROPTS_H */

#include "global.h"	/* For home_dir			      */
#include "tty.h"
#include "dir.h"	/* Required by panel.h below	      */
#include "util.h"	/* Required by panel.h		      */
#include "panel.h"	/* For WPanel and current_panel	      */
#include "dialog.h"	/* For query_dialog()		      */
#include "main.h"	/* For cpanel, quit & init_sigchld()  */
#include "cons.saver.h"	/* For handle_console(), etc.	      */
#include "key.h"	/* XCTRL and ALT macros		      */
#include "subshell.h"

#ifndef WEXITSTATUS
#   define WEXITSTATUS(stat_val) ((unsigned)(stat_val) >> 8)
#endif

#ifndef WIFEXITED
#   define WIFEXITED(stat_val) (((stat_val) & 255) == 0)
#endif

/* tcsh closes all non-standard file descriptors, so we have to use a pipe */
static char tcsh_fifo[128];

/* Local functions */
static void init_raw_mode (void);
static int feed_subshell (int how, int fail_on_error);
static void synchronize (void);
static int pty_open_master (char *pty_name);
static int pty_open_slave (const char *pty_name);
static int resize_tty (int fd);

/* }}} */
/* {{{ Definitions */

#ifndef STDIN_FILENO
#    define STDIN_FILENO 0
#endif

#ifndef STDOUT_FILENO
#    define STDOUT_FILENO 1
#endif

#ifndef STDERR_FILENO
#    define STDERR_FILENO 2
#endif

/* If using a subshell for evaluating commands this is true */
int use_subshell =
#ifdef SUBSHELL_OPTIONAL
FALSE;
#else
TRUE;
#endif

/* File descriptor of the pseudoterminal used by the subshell */
int subshell_pty = 0;

/* The key for switching back to MC from the subshell */
char subshell_switch_key = XCTRL('o');

/* State of the subshell:
 * INACTIVE: the default state; awaiting a command
 * ACTIVE: remain in the shell until the user hits `subshell_switch_key'
 * RUNNING_COMMAND: return to MC when the current command finishes */
enum subshell_state_enum subshell_state;

/* Holds the latest prompt captured from the subshell */
char *subshell_prompt = NULL;

/* Initial length of the buffer for the subshell's prompt */
#define INITIAL_PROMPT_SIZE 10

/* Used by the child process to indicate failure to start the subshell */
#define FORK_FAILURE 69  /* Arbitrary */

/* Initial length of the buffer for all I/O with the subshell */
#define INITIAL_PTY_BUFFER_SIZE 100  /* Arbitrary; but keep it >= 80 */

/* For pipes */
enum {READ=0, WRITE=1};


/* Local variables */

static char *pty_buffer;	/* For reading/writing on the subshell's pty */
static int pty_buffer_size;	/* The buffer grows as needed */
static int subshell_pipe[2];	/* To pass CWD info from the subshell to MC */
static pid_t subshell_pid = 1;	/* The subshell's process ID */
static char subshell_cwd[MC_MAXPATHLEN+1];  /* One extra char for final '\n' */

/* Subshell type (gleaned from the SHELL environment variable, if available) */
static enum {BASH, TCSH, ZSH} subshell_type;

/* Flag to indicate whether the subshell is ready for next command */
static int subshell_ready;

/* The following two flags can be changed by the SIGCHLD handler. This is */
/* OK, because the `int' type is updated atomically on all known machines */
static volatile int subshell_alive, subshell_stopped;

/* We store the terminal's initial mode here so that we can configure
   the pty similarly, and also so we can restore the real terminal to
   sanity if we have to exit abruptly */
static struct termios shell_mode;

/* This is a transparent mode for the terminal where MC is running on */
/* It is used when the shell is active, so that the control signals */
/* are delivered to the shell pty */
static struct termios raw_mode;

/* This counter indicates how many characters of prompt we have read */
/* FIXME: try to figure out why this had to become global */
static int prompt_pos;

/* }}} */

#ifdef HAVE_GRANTPT
#    define SYNC_PTY_SIDES
#else
#    define SYNC_PTY_SIDES
#endif

#undef SYNC_PTY_SIDES

#ifdef SYNC_PTY_SIDES
/* Handler for SIGUSR1 (used below), does nothing but accept the signal */
static void sigusr1_handler (int sig)
{
}
#endif

/*
 *  Prepare child process to running the shell and run it.
 *
 *  Modifies the global variables (in the child process only):
 *	shell_mode
 *
 *  Returns: never.
 */
static void init_subshell_child (const char *pty_name)
{
    int pty_slave;
    char *init_file = NULL;
	
    setsid ();  /* Get a fresh terminal session */

    /* {{{ Open the slave side of the pty: again */
    pty_slave = pty_open_slave (pty_name);

    /* This must be done before closing the master side of the pty, */
    /* or it will fail on certain idiotic systems, such as Solaris.	*/

    /* Close master side of pty.  This is important; apart from	*/
    /* freeing up the descriptor for use in the subshell, it also	*/
    /* means that when MC exits, the subshell will get a SIGHUP and	*/
    /* exit too, because there will be no more descriptors pointing	*/
    /* at the master side of the pty and so it will disappear.	*/

    close (subshell_pty);

#ifdef SYNC_PTY_SIDES
    /* Give our parent process (MC) the go-ahead */
    kill (getppid (), SIGUSR1);
#endif

    /* }}} */
    /* {{{ Make sure that it has become our controlling terminal */

    /* Redundant on Linux and probably most systems, but just in case: */

#ifdef TIOCSCTTY
    ioctl (pty_slave, TIOCSCTTY, 0);
#endif

    /* }}} */
    /* {{{ Configure its terminal modes and window size */

    /* Set up the pty with the same termios flags as our own tty, plus  */
    /* TOSTOP, which keeps background processes from writing to the pty */

    shell_mode.c_lflag |= TOSTOP;  /* So background writers get SIGTTOU */
    if (tcsetattr (pty_slave, TCSANOW, &shell_mode))
    {
        perror (__FILE__": couldn't set pty terminal modes");
        _exit (FORK_FAILURE);
    }

    /* Set the pty's size (80x25 by default on Linux) according to the */
    /* size of the real terminal as calculated by ncurses, if possible */
    resize_tty (pty_slave);

    /* }}} */
    /* {{{ Set up the subshell's environment and init file name */

    /* It simplifies things to change to our home directory here, */
    /* and the user's startup file may do a `cd' command anyway   */
    chdir (home_dir);  /* FIXME? What about when we re-run the subshell? */

    switch (subshell_type)
    {
        case BASH:
	    init_file = ".mc/bashrc";
	    if (access (init_file, R_OK) == -1)
		init_file = ".bashrc";

	    /* Make MC's special commands not show up in bash's history */
	    putenv ("HISTCONTROL=ignorespace");

	    /* Allow alternative readline settings for MC */
	    if (access (".mc/inputrc", R_OK) == 0)
		putenv ("INPUTRC=.mc/inputrc");

	    break;

	case TCSH:
	    init_file = ".mc/tcshrc";
	    if (access (init_file, R_OK) == -1)
		init_file += 3;
	break;

	case ZSH:
	    break;

	default:
	    fprintf (stderr, __FILE__": unimplemented subshell type %d\n",
		     subshell_type);
	    _exit (FORK_FAILURE);
    }

    /* }}} */
    /* {{{ Attach all our standard file descriptors to the pty */

    /* This is done just before the fork, because stderr must still	 */
    /* be connected to the real tty during the above error messages; */
    /* otherwise the user will never see them.			 */

    dup2 (pty_slave, STDIN_FILENO);
    dup2 (pty_slave, STDOUT_FILENO);
    dup2 (pty_slave, STDERR_FILENO);

    /* }}} */
    /* {{{ Execute the subshell at last */

    close (subshell_pipe[READ]);
    close (pty_slave);  /* These may be FD_CLOEXEC, but just in case... */

    switch (subshell_type)
    {
        case BASH:
	    execl (shell, "bash", "-rcfile", init_file, NULL);
	    break;

        case TCSH:
	    execl (shell, "tcsh", NULL);  /* What's the -rcfile equivalent? */
	    break;

        case ZSH:
	    /* change from "+Z" to "-Z" by Michael Bramer
	     * (Debian-mc-maintainer) <grisu@debian.org> from a patch from
	     * Radovan Garabik <garabik@center.fmph.uniba.sk>
	     */
	    execl (shell, "zsh", "-Z", NULL);

	    break;
    }

    /* If we get this far, everything failed miserably */
    _exit (FORK_FAILURE);

    /* }}} */
}

/* {{{ init_subshell */

/*
 *  Fork the subshell, and set up many, many things.
 *
 *  Possibly modifies the global variables:
 *	subshell_type, subshell_alive, subshell_stopped, subshell_pid
 *	use_subshell - Is set to FALSE if we can't run the subshell
 *	quit - Can be set to SUBSHELL_EXIT by the SIGCHLD handler
 */

void init_subshell (void)
{
    /* {{{ Local variables */

    /* This must be remembered across calls to init_subshell() */
    static char pty_name[BUF_SMALL];
    int pty_slave = -1;

    
#ifdef SYNC_PTY_SIDES
	/* Used to wait for a SIGUSR1 signal from the subprocess */
	sigset_t sigusr1_mask, old_mask;
#endif

    /* }}} */

    /* Take the current (hopefully pristine) tty mode and make */
    /* a raw mode based on it now, before we do anything else with it */
    init_raw_mode ();

    if (subshell_pty == 0)  /* First time through */
    {
	/* {{{ Find out what type of shell we have */

	if (strstr (shell, "/zsh"))
	    subshell_type = ZSH;
	else if (strstr (shell, "/tcsh"))
	    subshell_type = TCSH;
	else if (strstr (shell, "/bash") || getenv ("BASH"))
	    subshell_type = BASH;
	else
	{
	    use_subshell = FALSE;
	    return;
	}

	/* }}} */
	/* {{{ Open a pty for talking to the subshell */

	/* FIXME: We may need to open a fresh pty each time on SVR4 */

	subshell_pty = pty_open_master (pty_name);
	if (subshell_pty == -1)
	{
	    fputs (__FILE__": couldn't open master side of pty\n", stderr);
	    perror ("pty_open_master");
	    use_subshell = FALSE;
	    return;
	}
	pty_slave = pty_open_slave (pty_name);
	if (pty_slave == -1)
	{
	    fprintf (stderr, "couldn't open slave side of pty (%s)\n\r",
		     pty_name);
	    use_subshell = FALSE;
	    return;
	}


	/* }}} */
	/* {{{ Initialise the pty's I/O buffer */

	pty_buffer_size = INITIAL_PTY_BUFFER_SIZE;
	pty_buffer = (char *) g_malloc (pty_buffer_size);

	/* }}} */
	/* {{{ Create a pipe for receiving the subshell's CWD */

	if (subshell_type == TCSH)
	{
	    g_snprintf (tcsh_fifo, sizeof (tcsh_fifo), "%s/mc.pipe.%d",
			mc_tmpdir(), getpid ());
	    if (mkfifo (tcsh_fifo, 0600) == -1)
	    {
		perror (__FILE__": mkfifo");
		use_subshell = FALSE;
		return;
	    }

	    /* Opening the FIFO as O_RDONLY or O_WRONLY causes deadlock */

	    if ((subshell_pipe[READ] = open (tcsh_fifo, O_RDWR)) == -1 ||
		(subshell_pipe[WRITE] = open (tcsh_fifo, O_RDWR)) == -1)
	    {
		fprintf (stderr, _("Couldn't open named pipe %s\n"), tcsh_fifo);
		perror (__FILE__": open");
		use_subshell = FALSE;
		return;
	    }
	}
	else  /* subshell_type is BASH or ZSH */
	    if (pipe (subshell_pipe))
	    {
		perror (__FILE__": couldn't create pipe");
		use_subshell = FALSE;
		return;
	    }

	/* }}} */
    }

    /* {{{ Define a handler for the sigusr1 signal */

#ifdef SYNC_PTY_SIDES
	sigemptyset (&sigusr1_mask);
	sigaddset (&sigusr1_mask, SIGUSR1);
	sigprocmask (SIG_BLOCK, &sigusr1_mask, &old_mask);
	signal (SIGUSR1, sigusr1_handler);
#endif

    /* }}} */
    /* {{{ Fork the subshell */

    subshell_alive = TRUE;
    subshell_stopped = FALSE;
    subshell_pid = fork ();
    
    if (subshell_pid == -1)
    {
	perror (__FILE__": couldn't spawn the subshell process");
	/* We exit here because, if the process table is full, the */
	/* other method of running user commands won't work either */
	exit (1);
    }

   /* }}} */

    if (subshell_pid == 0)  /* We are in the child process */
    {
	init_subshell_child (pty_name);
    }

    /* pty_slave is only opened when called the first time */
    if (pty_slave != -1) {
	close(pty_slave);
    }

#ifdef SYNC_PTY_SIDES
	sigsuspend (&old_mask);
	signal (SIGUSR1, SIG_DFL);
	sigprocmask (SIG_SETMASK, &old_mask, NULL);
	/* ...before installing our handler for SIGCHLD. */
#endif

#if 0
    /* {{{ Install our handler for SIGCHLD */

    init_sigchld ();

    /* We could have received the SIGCHLD signal for the subshell 
     * before installing the init_sigchld */
    pid = waitpid (subshell_pid, &status, WUNTRACED | WNOHANG);
    if (pid == subshell_pid){
	use_subshell = FALSE;
	return;
    }

    /* }}} */
#endif

    /* {{{ Set up `precmd' or equivalent for reading the subshell's CWD */

    switch (subshell_type)
    {
	char precmd[BUF_SMALL];

	case BASH:
	g_snprintf (precmd, sizeof (precmd), " PROMPT_COMMAND='pwd>&%d;kill -STOP $$'\n",
		 subshell_pipe[WRITE]);
	goto write_it;

	case ZSH:
	g_snprintf (precmd, sizeof (precmd), "precmd(){ pwd>&%d;kill -STOP $$ }\n",
		 subshell_pipe[WRITE]);
	goto write_it;

	case TCSH:
	g_snprintf (precmd, sizeof (precmd),
		    "set echo_style=both;"
		    "alias precmd 'echo $cwd:q >>%s;kill -STOP $$'\n",
		    tcsh_fifo);

	write_it:
	write (subshell_pty, precmd, strlen (precmd));
    }

    /* }}} */
    /* {{{ Wait until the subshell has started up and processed the command */

    subshell_state = RUNNING_COMMAND;
    enable_interrupt_key ();
    if (!feed_subshell (QUIETLY, TRUE)){
	use_subshell = FALSE;
    }
    disable_interrupt_key ();
    if (!subshell_alive)
	use_subshell = FALSE;  /* Subshell died instantly, so don't use it */

    /* }}} */
}

/* }}} */

static void init_raw_mode ()
{
    static int initialized = 0;

    /* MC calls reset_shell_mode() in pre_exec() to set the real tty to its */
    /* original settings.  However, here we need to make this tty very raw, */
    /* so that all keyboard signals, XON/XOFF, etc. will get through to the */
    /* pty.  So, instead of changing the code for execute(), pre_exec(),    */
    /* etc, we just set up the modes we need here, before each command.     */

    if (initialized == 0)  /* First time: initialise `raw_mode' */
    {
	tcgetattr (STDOUT_FILENO, &raw_mode);
	raw_mode.c_lflag &= ~ICANON;  /* Disable line-editing chars, etc.   */
	raw_mode.c_lflag &= ~ISIG;    /* Disable intr, quit & suspend chars */
	raw_mode.c_lflag &= ~ECHO;    /* Disable input echoing		    */
	raw_mode.c_iflag &= ~IXON;    /* Pass ^S/^Q to subshell undisturbed */
	raw_mode.c_iflag &= ~ICRNL;   /* Don't translate CRs into LFs	    */
	raw_mode.c_oflag &= ~OPOST;   /* Don't postprocess output	    */
	raw_mode.c_cc[VTIME] = 0;     /* IE: wait forever, and return as    */
	raw_mode.c_cc[VMIN] = 1;      /* soon as a character is available   */
	initialized = 1;
    }
}

/* {{{ invoke_subshell */

int invoke_subshell (const char *command, int how, char **new_dir)
{
    /* {{{ Make the MC terminal transparent */

    tcsetattr (STDOUT_FILENO, TCSANOW, &raw_mode);

    /* }}} */
    
    /* Make the subshell change to MC's working directory */
    if (new_dir)
	do_subshell_chdir (cpanel->cwd, TRUE, 1);
    
    if (command == NULL)  /* The user has done "C-o" from MC */
    {
	if (subshell_state == INACTIVE)
	{
	    subshell_state = ACTIVE;
	    /* FIXME: possibly take out this hack; the user can
	       re-play it by hitting C-hyphen a few times! */
	    write (subshell_pty, " \b", 2);  /* Hack to make prompt reappear */
	}
    }
    else  /* MC has passed us a user command */
    {
	if (how == QUIETLY)
	    write (subshell_pty, " ", 1);
	/* FIXME: if command is long (>8KB ?) we go comma */
	write (subshell_pty, command, strlen (command));
	write (subshell_pty, "\n", 1);
	subshell_state = RUNNING_COMMAND;
	subshell_ready = FALSE;
    }

    feed_subshell (how, FALSE);

    if (new_dir && subshell_alive && strcmp (subshell_cwd, cpanel->cwd))
	*new_dir = subshell_cwd;  /* Make MC change to the subshell's CWD */

    /* Restart the subshell if it has died by SIGHUP, SIGQUIT, etc. */
    while (!subshell_alive && !quit && use_subshell)
	init_subshell ();

    prompt_pos = 0;

    return quit;
}

/* }}} */
/* {{{ read_subshell_prompt */

int read_subshell_prompt (void)
{
    /* {{{ Local variables */

    static int prompt_size = INITIAL_PROMPT_SIZE;
    int bytes = 0, i, rc = 0;
    struct timeval timeleft = {0, 0};

    fd_set tmp;
    FD_ZERO (&tmp);
    FD_SET (subshell_pty, &tmp);

    /* }}} */

    if (subshell_prompt == NULL)  /* First time through */
    {
	subshell_prompt = (char *) g_malloc (prompt_size);
	*subshell_prompt = '\0';
	prompt_pos = 0;
    }

    while (subshell_alive &&
	   (rc = select (subshell_pty + 1, &tmp, NULL, NULL, &timeleft)))
    {
	/* {{{ Check for `select' errors */

	if (rc == -1) {
	    if (errno == EINTR)
		continue;
	    else {
		tcsetattr (STDOUT_FILENO, TCSANOW, &shell_mode);
		perror ("\n"__FILE__": select (FD_SETSIZE, &tmp...)");
		exit (1);
	    }
	}

	/* }}} */

	bytes = read (subshell_pty, pty_buffer, pty_buffer_size);

	/* {{{ Extract the prompt from the shell output */

	for (i=0; i<bytes; ++i)
	    if (pty_buffer[i] == '\n' || pty_buffer[i] == '\r'){
		prompt_pos = 0;
	    } else {
		if (!pty_buffer [i])
		    continue;
		
		subshell_prompt[prompt_pos++] = pty_buffer[i];
		if (prompt_pos == prompt_size)
		    subshell_prompt = (char *) g_realloc (subshell_prompt,
							prompt_size *= 2);
	    }

	subshell_prompt[prompt_pos] = '\0';

	/* }}} */
    }
    if (rc == 0 && bytes == 0)
	return FALSE;
    return TRUE;
}

/* Resize given terminal using TIOCSWINSZ, return ioctl() result */
static int resize_tty (int fd)
{
#if defined TIOCSWINSZ && !defined SCO_FLAVOR
    struct winsize tty_size;

    tty_size.ws_row = LINES;
    tty_size.ws_col = COLS;
    tty_size.ws_xpixel = tty_size.ws_ypixel = 0;

    return ioctl (fd, TIOCSWINSZ, &tty_size);
#endif
}

/* Resize subshell_pty */
void resize_subshell (void)
{
    resize_tty (subshell_pty);
}

int exit_subshell (void)
{
    int quit = TRUE;
    
    if (subshell_state != INACTIVE && subshell_alive)
	quit = !query_dialog (_("Warning"), _(" The shell is still active. Quit anyway? "),
			      0, 2, _("&Yes"), _("&No"));

    if (quit && subshell_type == TCSH)
    {
	if (unlink (tcsh_fifo) == -1)
	    perror (__FILE__": couldn't remove named pipe /tmp/mc.pipe.NNN");
    }

    g_free (subshell_prompt);
    subshell_prompt = NULL;

    return quit;
}

/* }}} */

/*
 * Carefully quote directory name to allow entering any directory safely,
 * no matter what weird characters it may contain in its name.
 * NOTE: Treat directory name an untrusted data, don't allow it to cause
 * executing any commands in the shell.  Escape all control characters.
 * Use following technique:
 *
 * for bash - echo with `-e', 3-digit octal numbers:
 *   cd "`echo -e '\ooo...\ooo'`"
 *
 * for zsh - echo with `-e', 4-digit octal numbers:
 *   cd "`echo '\oooo...\oooo'`"
 *
 * for tcsh - echo without `-e', 4-digit octal numbers:
 *   cd "`echo '\oooo...\oooo'`"
 */
static char *
subshell_name_quote (const char *s)
{
    char *ret, *d;
    const char echo_cmd[] = "\"`echo '";
    const char echo_e_cmd[] = "\"`echo -e '";
    const char common_end[] = "'`\"";
    const char *cmd_start;
    int len;

    /*
     * Factor 5 because we need \, 0 and 3 other digits per character
     * in the worst case (tcsh and zsh).
     */
    d = ret = g_malloc (5 * strlen (s) + 16);
    if (!d)
	return NULL;

    /* Prevent interpreting leading `-' as a switch for `cd' */
    if (*s == '-') {
        *d++ = '.';
        *d++ = '/';
    }

    /* echo in tcsh doesn't understand the "-e" option */
    if (subshell_type == TCSH)
	cmd_start = echo_cmd;
    else
	cmd_start = echo_e_cmd;

    /* Copy the beginning of the command to the buffer */
    len = strlen (cmd_start);
    memcpy (d, cmd_start, len);
    d += len;

    /*
     * Print every character in octal format with the leading backslash.
     * tcsh and zsh may require 4-digit octals, bash doesn't like them.
     */
    if (subshell_type == BASH) {
	for (; *s; s++) {
	    sprintf(d, "\\%03o", (unsigned char) *s);
	    d += 4;
	}
    } else {
	for (; *s; s++) {
	    sprintf(d, "\\0%03o", (unsigned char) *s);
	    d += 5;
	}
    }

    memcpy (d, common_end, sizeof (common_end));

    return ret;
}



/* {{{ do_subshell_chdir */
/* If it actually changed the directory it returns true */
void do_subshell_chdir (const char *directory, int do_update, int reset_prompt)
{
    if (!(subshell_state == INACTIVE && strcmp (subshell_cwd, cpanel->cwd))){
	/* We have to repaint the subshell prompt if we read it from
	 * the main program.  Please note that in the code after this
	 * if, the cd command that is sent will make the subshell
	 * repaint the prompt, so we don't have to paint it. */
	if (do_update)
	    do_update_prompt ();
	return;
    }
    
    /* The initial space keeps this out of the command history (in bash
       because we set "HISTCONTROL=ignorespace") */
    write (subshell_pty, " cd ", 4);
    if (*directory) {
	char *temp;
	temp = subshell_name_quote (directory);
	if (temp) {
	    write (subshell_pty, temp, strlen (temp));
	    g_free (temp);
	} else {
	    /* Should not happen unless the directory name is so long
	       that we don't have memory to quote it.  */
	    write (subshell_pty, ".", 1);
	}
    } else {
	write (subshell_pty, "/", 1);
    }
    write (subshell_pty, "\n", 1);
    
    subshell_state = RUNNING_COMMAND;
    feed_subshell (QUIETLY, FALSE);
    
    if (subshell_alive && strcmp (subshell_cwd, cpanel->cwd) && strcmp (cpanel->cwd, "."))
	fprintf (stderr, _("Warning: Couldn't change to %s.\n"), cpanel->cwd);

    if (reset_prompt)
	prompt_pos = 0;
    update_prompt = FALSE;
    /* Make sure that MC never stores the CWD in a silly format */
    /* like /usr////lib/../bin, or the strcmp() above will fail */
}

/* }}} */
/* {{{ subshell_get_console_attributes */

void subshell_get_console_attributes (void)
{
    /* {{{ Get our current terminal modes */

    if (tcgetattr (STDOUT_FILENO, &shell_mode))
    {
	perror (__FILE__": couldn't get terminal settings");
	use_subshell = FALSE;
	return;
    }

    /* }}} */
}

/* }}} */
/* {{{ sigchld_handler */

/* Figure out whether the subshell has stopped, exited or been killed */
/* Possibly modifies: `subshell_alive', `subshell_stopped' and `quit' */

void sigchld_handler (int sig)
{
    int status;
    pid_t pid;

    pid = waitpid (subshell_pid, &status, WUNTRACED | WNOHANG);

    if (pid == subshell_pid) {
	/* {{{ Figure out what has happened to the subshell */

	if (WIFSTOPPED (status))
	{
	    if (WSTOPSIG (status) == SIGSTOP) {
		/* The subshell has received a SIGSTOP signal */
		subshell_stopped = TRUE;
	    } else {
		/* The user has suspended the subshell.  Revive it */
		kill (subshell_pid, SIGCONT);
	    }
	}
	else  /* The subshell has either exited normally or been killed */
	{
	    subshell_alive = FALSE;
	    delete_select_channel (subshell_pty);
	    if (WIFEXITED (status) && WEXITSTATUS (status) != FORK_FAILURE)
		quit |= SUBSHELL_EXIT;  /* Exited normally */
	}

	/* }}} */
    }

#if defined(linux) || defined(__linux__)
    pid = waitpid (cons_saver_pid, &status, WUNTRACED | WNOHANG);
    
    if (pid == cons_saver_pid) {

	if (WIFSTOPPED (status))
	    /* Someone has stopped cons.saver - restart it */
	    kill (pid, SIGCONT);
	else
	{
	    /* cons.saver has died - disable confole saving */
	    handle_console (CONSOLE_DONE);
	    console_flag = 0;
	}

    }
#endif /* linux || __linux__ */
    /* If we get here, some other child exited; ignore it */
#  ifdef __EMX__				/* Need to report */
    pid = wait(&status);
#  endif
}

/* }}} */

/* {{{ feed_subshell */

/* Feed the subshell our keyboard input until it says it's finished */

static int feed_subshell (int how, int fail_on_error)
{
    /* {{{ Local variables */
    fd_set read_set;	/* For `select' */
    int maxfdp;
    int bytes;		/* For the return value from `read' */
    int i;		/* Loop counter */
    
    struct timeval wtime; /* Maximum time we wait for the subshell */
    struct timeval *wptr;
    /* }}} */

    /* we wait up to 10 seconds if fail_on_error, forever otherwise */
    wtime.tv_sec = 10;
    wtime.tv_usec = 0;
    wptr = fail_on_error ? &wtime : NULL;
    
    while (1) {
	if (!subshell_alive)
	    return FALSE;

	/* {{{ Prepare the file-descriptor set and call `select' */

	FD_ZERO (&read_set);
	FD_SET (subshell_pty, &read_set);
	FD_SET (subshell_pipe[READ], &read_set);
	maxfdp = max (subshell_pty, subshell_pipe[READ]);
	if (how == VISIBLY) {
	    FD_SET (STDIN_FILENO, &read_set);
	    maxfdp = max (maxfdp, STDIN_FILENO);
	}

	if (select (maxfdp + 1, &read_set, NULL, NULL, wptr) == -1){

	    /* Despite using SA_RESTART, we still have to check for this */
	    if (errno == EINTR)
		continue;	/* try all over again */
	    tcsetattr (STDOUT_FILENO, TCSANOW, &shell_mode);
	    perror ("\n"__FILE__": select (FD_SETSIZE, &read_set...)");
	    exit (1);
	}
	/* }}} */

	if (FD_ISSET (subshell_pty, &read_set))
	    /* {{{ Read from the subshell, write to stdout */

	    /* This loop improves performance by reducing context switches
               by a factor of 20 or so... unfortunately, it also hangs MC
               randomly, because of an apparent Linux bug.  Investigate. */
	    /* for (i=0; i<5; ++i)  * FIXME -- experimental */
	    {
		bytes = read (subshell_pty, pty_buffer, pty_buffer_size);

		/* The subshell has died */
                if (bytes == -1 && errno == EIO && !subshell_alive)
                    return FALSE;

                if (bytes <= 0)
		{
		    tcsetattr (STDOUT_FILENO, TCSANOW, &shell_mode);
		    perror ("\n"__FILE__": read (subshell_pty...)");
		    exit (1);
		}

		if (how == VISIBLY)
		    write (STDOUT_FILENO, pty_buffer, bytes);
	    }

	    /* }}} */

	else if (FD_ISSET (subshell_pipe[READ], &read_set))
	    /* {{{ Read the subshell's CWD and capture its prompt */

	    {
		bytes = read (subshell_pipe[READ], subshell_cwd, MC_MAXPATHLEN+1);
		if (bytes <= 0)
		{
		    tcsetattr (STDOUT_FILENO, TCSANOW, &shell_mode);
		    perror ("\n"__FILE__": read (subshell_pipe[READ]...)");
		    exit (1);
		}

		subshell_cwd[bytes-1] = 0;  /* Squash the final '\n' */

		synchronize ();

		subshell_ready = TRUE;
		if (subshell_state == RUNNING_COMMAND)
		{
		    subshell_state = INACTIVE;
		    return 1;
		}
	    }

	    /* }}} */

	else if (FD_ISSET (STDIN_FILENO, &read_set))
	    /* {{{ Read from stdin, write to the subshell */

	    {
		bytes = read (STDIN_FILENO, pty_buffer, pty_buffer_size);
		if (bytes <= 0)
		{
		    tcsetattr (STDOUT_FILENO, TCSANOW, &shell_mode);
		    perror ("\n"__FILE__": read (STDIN_FILENO, pty_buffer...)");
		    exit (1);
		}

		for (i=0; i<bytes; ++i)
		    if (pty_buffer[i] == subshell_switch_key)
		    {
			write (subshell_pty, pty_buffer, i);
			if (subshell_ready)
			    subshell_state = INACTIVE;
			return TRUE;
		    }

		write (subshell_pty, pty_buffer, bytes);
		subshell_ready = FALSE;
	    } else {
		return FALSE;
	    }

	    /* }}} */
    }
}

/* }}} */
/* {{{ synchronize */

/* Wait until the subshell dies or stops.  If it stops, make it resume.  */
/* Possibly modifies the globals `subshell_alive' and `subshell_stopped' */

static void synchronize (void)
{
    sigset_t sigchld_mask, old_mask;

    sigemptyset (&sigchld_mask);
    sigaddset (&sigchld_mask, SIGCHLD);
    sigprocmask (SIG_BLOCK, &sigchld_mask, &old_mask);

    /*
     * SIGCHLD should not be blocked, but we unblock it just in case.
     * This is known to be useful for cygwin 1.3.12 and older.
     */
    sigdelset (&old_mask, SIGCHLD);

    /* Wait until the subshell has stopped */
    while (subshell_alive && !subshell_stopped)
	sigsuspend (&old_mask);

    /* Discard all remaining data from stdin to the subshell */
    tcflush (subshell_pty, TCOFLUSH);

    subshell_stopped = FALSE;
    kill (subshell_pid, SIGCONT);

    sigprocmask (SIG_SETMASK, &old_mask, NULL);
    /* We can't do any better without modifying the shell(s) */
}

/* }}} */
/* {{{ pty opening functions */

#ifdef SCO_FLAVOR

/* {{{ SCO version of pty_open_master */

static int pty_open_master (char *pty_name)
{
    int pty_master;
    int num;
    char *ptr;

    strcpy (pty_name, "/dev/ptyp");
    ptr = pty_name+9;
    for (num=0;;num++)
    {
	g_snprintf(ptr, 9, "%d",num);	/* surpriiise ... SCO lacks itoa() */
	/* Try to open master */
	if ((pty_master = open (pty_name, O_RDWR)) == -1) {
	    if (errno == ENOENT)  /* Different from EIO */
		return -1;	      /* Out of pty devices */
	    else
		continue;	      /* Try next pty device */
	}
	pty_name [5] = 't';	      /* Change "pty" to "tty" */
	if (access (pty_name, 6)){
	    close (pty_master);
	    pty_name [5] = 'p';
	    continue;
	}
	return pty_master;
    }
    return -1;  /* Ran out of pty devices */
}

/* }}} */
/* {{{ SCO version of pty_open_slave */

static int pty_open_slave (const char *pty_name)
{
    int pty_slave;
    struct group *group_info = getgrnam ("terminal");
    
    if (group_info != NULL)
    {
	/* The following two calls will only succeed if we are root */
	/* [Commented out while permissions problem is investigated] */
	/* chown (pty_name, getuid (), group_info->gr_gid);  FIXME */
	/* chmod (pty_name, S_IRUSR | S_IWUSR | S_IWGRP);   FIXME */
    }
    if ((pty_slave = open (pty_name, O_RDWR)) == -1)
	perror ("open (pty_name, O_RDWR)");
    return pty_slave;
}

/* }}} */

#elif HAVE_GRANTPT /* !HAVE_SCO */

/* {{{ System V version of pty_open_master */

static int pty_open_master (char *pty_name)
{
    char *slave_name;
    int pty_master;


#ifdef HAVE_GETPT
    /* getpt () is a GNU extension (glibc 2.1.x) */
    pty_master = getpt ();
#elif IS_AIX
    strcpy (pty_name, "/dev/ptc");
    pty_master = open (pty_name, O_RDWR);
#else
    strcpy (pty_name, "/dev/ptmx");
    pty_master = open (pty_name, O_RDWR);
#endif 
    if (pty_master == -1)
	return -1;

    if (grantpt (pty_master) == -1		  /* Grant access to slave */
	|| unlockpt (pty_master) == -1		  /* Clear slave's lock flag */
	|| !(slave_name = ptsname (pty_master)))  /* Get slave's name */
    {
	close (pty_master);
	return -1;
    }
    strcpy (pty_name, slave_name);
    return pty_master;
}

/* }}} */
/* {{{ System V version of pty_open_slave */

static int pty_open_slave (const char *pty_name)
{
    int pty_slave = open (pty_name, O_RDWR);

    if (pty_slave == -1)
    {
	perror ("open (pty_name, O_RDWR)");
	return -1;
    }

#if !defined(__osf__) && !defined(linux) && !defined(__linux__)
#if defined (I_FIND) && defined (I_PUSH)
    if (!ioctl (pty_slave, I_FIND, "ptem"))
	if (ioctl (pty_slave, I_PUSH, "ptem") == -1)
	{
	    fprintf (stderr, "ioctl (pty_slave, I_PUSH, \"ptem\") failed\n");
	    close (pty_slave);
	    return -1;
	}
	
    if (!ioctl (pty_slave, I_FIND, "ldterm"))
        if (ioctl (pty_slave, I_PUSH, "ldterm") == -1)
	{
	    fprintf (stderr, "ioctl (pty_slave, I_PUSH, \"ldterm\") failed\n");
	    close (pty_slave);
	    return -1;
	}

#if !defined(sgi) && !defined(__sgi)
    if (!ioctl (pty_slave, I_FIND, "ttcompat"))
        if (ioctl (pty_slave, I_PUSH, "ttcompat") == -1)
	{
	    fprintf (stderr, "ioctl (pty_slave, I_PUSH, \"ttcompat\") failed\n");
	    close (pty_slave);
	    return -1;
	}
#endif /* sgi || __sgi */
#endif /* I_FIND && I_PUSH */
#endif /* __osf__ || linux || __linux__ */

    return pty_slave;
}

/* }}} */

#else /* !HAVE_SCO && !HAVE_GRANTPT */

/* {{{ BSD version of pty_open_master */

static int pty_open_master (char *pty_name)
{
    int pty_master;
    char *ptr1, *ptr2;

    strcpy (pty_name, "/dev/ptyXX");
    for (ptr1 = "pqrstuvwxyzPQRST"; *ptr1; ++ptr1)
    {
	pty_name [8] = *ptr1;
	for (ptr2 = "0123456789abcdef"; *ptr2; ++ptr2)
	{
	    pty_name [9] = *ptr2;

	    /* Try to open master */
	    if ((pty_master = open (pty_name, O_RDWR)) == -1) {
		if (errno == ENOENT)  /* Different from EIO */
		    return -1;	      /* Out of pty devices */
		else
		    continue;	      /* Try next pty device */
	    }
	    pty_name [5] = 't';	      /* Change "pty" to "tty" */
	    if (access (pty_name, 6)){
		close (pty_master);
		pty_name [5] = 'p';
		continue;
	    }
	    return pty_master;
	}
    }
    return -1;  /* Ran out of pty devices */
}

/* }}} */
/* {{{ BSD version of pty_open_slave */

static int pty_open_slave (const char *pty_name)
{
    int pty_slave;
    struct group *group_info = getgrnam ("tty");

    if (group_info != NULL)
    {
	/* The following two calls will only succeed if we are root */
	/* [Commented out while permissions problem is investigated] */
	/* chown (pty_name, getuid (), group_info->gr_gid);  FIXME */
	/* chmod (pty_name, S_IRUSR | S_IWUSR | S_IWGRP);   FIXME */
    }
    if ((pty_slave = open (pty_name, O_RDWR)) == -1)
	perror ("open (pty_name, O_RDWR)");
    return pty_slave;
}

/* }}} */

#endif /* !HAVE_SCO && !HAVE_GRANTPT */

/* }}} */

#endif /* HAVE_SUBSHELL_SUPPORT */

/* {{{ Emacs local variables */

/*
  Cause emacs to enter folding mode for this file:
  Local variables:
  end:
*/

/* }}} */