emacs/lib-src/emacsclient.c

/* Client process that communicates with GNU Emacs acting as server.

Copyright (C) 1986-1987, 1994, 1999-2018 Free Software Foundation, Inc.

This file is part of GNU Emacs.

GNU Emacs is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.

GNU Emacs 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 GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.  */


#include <config.h>

#ifdef WINDOWSNT

/* ms-w32.h defines these, which disables sockets altogether!  */
# undef _WINSOCKAPI_
# undef _WINSOCK_H

# include <malloc.h>
# include <windows.h>
# include <commctrl.h>
# include <io.h>
# include <winsock2.h>

# define NO_SOCKETS_IN_FILE_SYSTEM

# define HSOCKET SOCKET
# define CLOSE_SOCKET closesocket
# define INITIALIZE() initialize_sockets ()

char *w32_getenv (const char *);
# define egetenv(VAR) w32_getenv (VAR)

#else /* !WINDOWSNT */

# ifdef HAVE_NTGUI
# include <windows.h>
# endif /* HAVE_NTGUI */

# include "syswait.h"

# ifdef HAVE_INET_SOCKETS
#  include <netinet/in.h>
#  ifdef HAVE_SOCKETS
#    include <sys/types.h>
#    include <sys/socket.h>
#    include <sys/un.h>
#  endif /* HAVE_SOCKETS */
# endif
# include <arpa/inet.h>

# define INVALID_SOCKET (-1)
# define HSOCKET int
# define CLOSE_SOCKET close
# define INITIALIZE()

# define egetenv(VAR) getenv (VAR)

#endif /* !WINDOWSNT */

#undef signal

#include <ctype.h>
#include <errno.h>
#include <getopt.h>
#include <inttypes.h>
#include <pwd.h>
#include <signal.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>

#include <dosname.h>
#include <intprops.h>
#include <min-max.h>
#include <unlocked-io.h>

#ifndef VERSION
#define VERSION "unspecified"
#endif


/* Name used to invoke this program.  */
static char const *progname;

/* The first argument to main.  */
static int main_argc;

/* The second argument to main.  */
static char *const *main_argv;

/* True means don't wait for a response from Emacs.  --no-wait.  */
static bool nowait;

/* True means don't print messages for successful operations.  --quiet.  */
static bool quiet;

/* True means don't print values returned from emacs. --suppress-output.  */
static bool suppress_output;

/* True means args are expressions to be evaluated.  --eval.  */
static bool eval;

/* True means open a new frame.  --create-frame etc.  */
static bool create_frame;

/* The display on which Emacs should work.  --display.  */
static char const *display;

/* The alternate display we should try if Emacs does not support display.  */
static char const *alt_display;

/* The parent window ID, if we are opening a frame via XEmbed.  */
static char *parent_id;

/* True means open a new Emacs frame on the current terminal.  */
static bool tty;

/* If non-NULL, the name of an editor to fallback to if the server
   is not running.  --alternate-editor.   */
static char *alternate_editor;

#ifndef NO_SOCKETS_IN_FILE_SYSTEM
/* If non-NULL, the filename of the UNIX socket.  */
static char const *socket_name;
#endif

/* If non-NULL, the filename of the authentication file.  */
static char const *server_file;

/* If non-NULL, the tramp prefix emacs must use to find the files.  */
static char const *tramp_prefix;

/* PID of the Emacs server process.  */
static pid_t emacs_pid;

/* If non-NULL, a string that should form a frame parameter alist to
   be used for the new frame.  */
static char const *frame_parameters;

static _Noreturn void print_help_and_exit (void);

/* Long command-line options.  */

static struct option const longopts[] =
{
  { "no-wait",	no_argument,	   NULL, 'n' },
  { "quiet",	no_argument,	   NULL, 'q' },
  { "suppress-output", no_argument, NULL, 'u' },
  { "eval",	no_argument,	   NULL, 'e' },
  { "help",	no_argument,	   NULL, 'H' },
  { "version",	no_argument,	   NULL, 'V' },
  { "tty",	no_argument,       NULL, 't' },
  { "nw",	no_argument,       NULL, 't' },
  { "create-frame", no_argument,   NULL, 'c' },
  { "alternate-editor", required_argument, NULL, 'a' },
  { "frame-parameters", required_argument, NULL, 'F' },
#ifndef NO_SOCKETS_IN_FILE_SYSTEM
  { "socket-name",	required_argument, NULL, 's' },
#endif
  { "server-file",	required_argument, NULL, 'f' },
  { "display",	required_argument, NULL, 'd' },
  { "parent-id", required_argument, NULL, 'p' },
  { "tramp",	required_argument, NULL, 'T' },
  { 0, 0, 0, 0 }
};

/* Short options, in the same order as the corresponding long options.
   There is no '-p' short option.  */
static char const shortopts[] =
  "nqueHVtca:F:"
#ifndef NO_SOCKETS_IN_FILE_SYSTEM
  "s:"
#endif
  "f:d:T:";


/* Like malloc but get fatal error if memory is exhausted.  */

static void * ATTRIBUTE_MALLOC
xmalloc (size_t size)
{
  void *result = malloc (size);
  if (result == NULL)
    {
      perror ("malloc");
      exit (EXIT_FAILURE);
    }
  return result;
}

/* Like realloc but get fatal error if memory is exhausted.  */

static void *
xrealloc (void *ptr, size_t size)
{
  void *result = realloc (ptr, size);
  if (result == NULL)
    {
      perror ("realloc");
      exit (EXIT_FAILURE);
    }
  return result;
}

/* Like strdup but get a fatal error if memory is exhausted. */

static char * ATTRIBUTE_MALLOC
xstrdup (const char *s)
{
  char *result = strdup (s);
  if (result == NULL)
    {
      perror ("strdup");
      exit (EXIT_FAILURE);
    }
  return result;
}

/* From sysdep.c */
#if !defined HAVE_GET_CURRENT_DIR_NAME || defined BROKEN_GET_CURRENT_DIR_NAME

char *get_current_dir_name (void);

/* Return the current working directory.  Returns NULL on errors.
   Any other returned value must be freed with free.  This is used
   only when get_current_dir_name is not defined on the system.  */
char *
get_current_dir_name (void)
{
  char *buf;
  struct stat dotstat, pwdstat;
  /* If PWD is accurate, use it instead of calling getcwd.  PWD is
     sometimes a nicer name, and using it may avoid a fatal error if a
     parent directory is searchable but not readable.  */
  char const *pwd = egetenv ("PWD");
  if (pwd
      && (IS_DIRECTORY_SEP (*pwd) || (*pwd && IS_DEVICE_SEP (pwd[1])))
      && stat (pwd, &pwdstat) == 0
      && stat (".", &dotstat) == 0
      && dotstat.st_ino == pwdstat.st_ino
      && dotstat.st_dev == pwdstat.st_dev
# ifdef MAXPATHLEN
      && strlen (pwd) < MAXPATHLEN
# endif
      )
    {
      buf = xmalloc (strlen (pwd) + 1);
      strcpy (buf, pwd);
    }
  else
    {
      size_t buf_size = 1024;
      for (;;)
        {
	  int tmp_errno;
	  buf = malloc (buf_size);
	  if (! buf)
	    break;
          if (getcwd (buf, buf_size) == buf)
            break;
	  tmp_errno = errno;
	  free (buf);
	  if (tmp_errno != ERANGE)
            {
              errno = tmp_errno;
              return NULL;
            }
          buf_size *= 2;
	  if (! buf_size)
	    {
	      errno = ENOMEM;
	      return NULL;
	    }
        }
    }
  return buf;
}
#endif

#ifdef WINDOWSNT

# define REG_ROOT "SOFTWARE\\GNU\\Emacs"

char *w32_get_resource (HKEY, const char *, LPDWORD);

/* Retrieve an environment variable from the Emacs subkeys of the registry.
   Return NULL if the variable was not found, or it was empty.
   This code is based on w32_get_resource (w32.c).  */
char *
w32_get_resource (HKEY predefined, const char *key, LPDWORD type)
{
  HKEY hrootkey = NULL;
  char *result = NULL;
  DWORD cbData;

  if (RegOpenKeyEx (predefined, REG_ROOT, 0, KEY_READ, &hrootkey)
      == ERROR_SUCCESS)
    {
      if (RegQueryValueEx (hrootkey, key, NULL, NULL, NULL, &cbData)
	  == ERROR_SUCCESS)
	{
	  result = xmalloc (cbData);

	  if ((RegQueryValueEx (hrootkey, key, NULL, type, (LPBYTE) result,
				&cbData)
	       != ERROR_SUCCESS)
	      || *result == 0)
	    {
	      free (result);
	      result = NULL;
	    }
	}

      RegCloseKey (hrootkey);
    }

  return result;
}

/*
  getenv wrapper for Windows

  Value is allocated on the heap, and can be free'd.

  This is needed to duplicate Emacs's behavior, which is to look for
  environment variables in the registry if they don't appear in the
  environment.  */
char *
w32_getenv (const char *envvar)
{
  char *value;
  DWORD dwType;

  if ((value = getenv (envvar)))
    /* Found in the environment.  strdup it, because values returned
       by getenv cannot be free'd.  */
    return xstrdup (value);

  if (! (value = w32_get_resource (HKEY_CURRENT_USER, envvar, &dwType)) &&
      ! (value = w32_get_resource (HKEY_LOCAL_MACHINE, envvar, &dwType)))
    {
      /* "w32console" is what Emacs on Windows uses for tty-type under -nw.  */
      if (strcmp (envvar, "TERM") == 0)
	return xstrdup ("w32console");
      /* Found neither in the environment nor in the registry.  */
      return NULL;
    }

  if (dwType == REG_SZ)
    /* Registry; no need to expand.  */
    return value;

  if (dwType == REG_EXPAND_SZ)
    {
      DWORD size;

      if ((size = ExpandEnvironmentStrings (value, NULL, 0)))
	{
	  char *buffer = xmalloc (size);
	  if (ExpandEnvironmentStrings (value, buffer, size))
	    {
	      /* Found and expanded.  */
	      free (value);
	      return buffer;
	    }

	  /* Error expanding.  */
	  free (buffer);
	}
    }

  /* Not the right type, or not correctly expanded.  */
  free (value);
  return NULL;
}

int w32_window_app (void);

int
w32_window_app (void)
{
  static int window_app = -1;
  char szTitle[MAX_PATH];

  if (window_app < 0)
    {
      /* Checking for STDOUT does not work; it's a valid handle also in
         nonconsole apps.  Testing for the console title seems to work. */
      window_app = (GetConsoleTitleA (szTitle, MAX_PATH) == 0);
      if (window_app)
        InitCommonControls ();
    }

  return window_app;
}

/* execvp wrapper for Windows.  Quotes arguments with embedded spaces.

  This is necessary due to the broken implementation of exec* routines in
  the Microsoft libraries: they concatenate the arguments together without
  quoting special characters, and pass the result to CreateProcess, with
  predictably bad results.  By contrast, POSIX execvp passes the arguments
  directly into the argv array of the child process.  */

int w32_execvp (const char *, char **);

int
w32_execvp (const char *path, char **argv)
{
  int i;

  /* Required to allow a .BAT script as alternate editor.  */
  argv[0] = (char *) alternate_editor;

  for (i = 0; argv[i]; i++)
    if (strchr (argv[i], ' '))
      {
	char *quoted = alloca (strlen (argv[i]) + 3);
	sprintf (quoted, "\"%s\"", argv[i]);
	argv[i] = quoted;
      }

  return execvp (path, argv);
}

# undef execvp
# define execvp w32_execvp

/* Emulation of ttyname for Windows.  */
const char *ttyname (int);
const char *
ttyname (int fd)
{
  return "CONOUT$";
}

#endif /* WINDOWSNT */

/* Display a normal or error message.
   On Windows, use a message box if compiled as a Windows app.  */
static void message (bool, const char *, ...) ATTRIBUTE_FORMAT_PRINTF (2, 3);
static void
message (bool is_error, const char *format, ...)
{
  va_list args;

  va_start (args, format);

#ifdef WINDOWSNT
  if (w32_window_app ())
    {
      char msg[2048];
      vsnprintf (msg, sizeof msg, format, args);
      msg[sizeof msg - 1] = '\0';

      if (is_error)
	MessageBox (NULL, msg, "Emacsclient ERROR", MB_ICONERROR);
      else
	MessageBox (NULL, msg, "Emacsclient", MB_ICONINFORMATION);
    }
  else
#endif
    {
      FILE *f = is_error ? stderr : stdout;

      vfprintf (f, format, args);
      fflush (f);
    }

  va_end (args);
}

/* Decode the options from argv and argc.
   The global variable 'optind' will say how many arguments we used up.  */

static void
decode_options (int argc, char **argv)
{
  alternate_editor = egetenv ("ALTERNATE_EDITOR");
  tramp_prefix = egetenv ("EMACSCLIENT_TRAMP");

  while (true)
    {
      int opt = getopt_long_only (argc, argv, shortopts, longopts, NULL);
      if (opt < 0)
	break;

      switch (opt)
	{
	case 0:
	  /* If getopt returns 0, then it has already processed a
	     long-named option.  We should do nothing.  */
	  break;

	case 'a':
	  alternate_editor = optarg;
	  break;

#ifndef NO_SOCKETS_IN_FILE_SYSTEM
	case 's':
	  socket_name = optarg;
	  break;
#endif

	case 'f':
	  server_file = optarg;
	  break;

	  /* We used to disallow this argument in w32, but it seems better
	     to allow it, for the occasional case where the user is
	     connecting with a w32 client to a server compiled with X11
	     support.  */
	case 'd':
	  display = optarg;
	  break;

	case 'n':
	  nowait = true;
	  break;

	case 'e':
	  eval = true;
	  break;

	case 'q':
	  quiet = true;
	  break;

	case 'u':
	  suppress_output = true;
	  break;

	case 'V':
	  message (false, "emacsclient %s\n", VERSION);
	  exit (EXIT_SUCCESS);
	  break;

        case 't':
	  tty = true;
	  create_frame = true;
          break;

        case 'c':
	  create_frame = true;
          break;

	case 'p':
	  parent_id = optarg;
	  create_frame = true;
	  break;

	case 'H':
	  print_help_and_exit ();
	  break;

        case 'F':
          frame_parameters = optarg;
          break;

        case 'T':
          tramp_prefix = optarg;
          break;

	default:
	  message (true, "Try '%s --help' for more information\n", progname);
	  exit (EXIT_FAILURE);
	  break;
	}
    }

  /* If the -c option is used (without -t) and no --display argument
     is provided, try $DISPLAY.
     Without the -c option, we used to set 'display' to $DISPLAY by
     default, but this changed the default behavior and is sometimes
     inconvenient.  So we force users to use "--display $DISPLAY" if
     they want Emacs to connect to their current display.

     Some window systems have a notion of default display not
     reflected in the DISPLAY variable.  If the user didn't give us an
     explicit display, try this platform-specific after trying the
     display in DISPLAY (if any).  */
  if (create_frame && !tty && !display)
    {
      /* Set these here so we use a default_display only when the user
         didn't give us an explicit display.  */
#if defined (NS_IMPL_COCOA)
      alt_display = "ns";
#elif defined (HAVE_NTGUI)
      alt_display = "w32";
#endif

      display = egetenv ("DISPLAY");
    }

  if (!display)
    {
      display = alt_display;
      alt_display = NULL;
    }

  /* A null-string display is invalid.  */
  if (display && !display[0])
    display = NULL;

  /* If no display is available, new frames are tty frames.  */
  if (create_frame && !display)
    tty = true;

#ifdef WINDOWSNT
  /* Emacs on Windows does not support graphical and text terminal
     frames in the same instance.  So, treat the -t and -c options as
     equivalent, and open a new frame on the server's terminal.
     Ideally, we would set tty = true only if the server is running in a
     console, but alas we don't know that.  As a workaround, always
     ask for a tty frame, and let server.el figure it out.  */
  if (create_frame)
    {
      display = NULL;
      tty = true;
    }
#endif /* WINDOWSNT */
}


static _Noreturn void
print_help_and_exit (void)
{
  /* Spaces and tabs are significant in this message; they're chosen so the
     message aligns properly both in a tty and in a Windows message box.
     Please try to preserve them; otherwise the output is very hard to read
     when using emacsclientw.  */
  message (false,
	   "Usage: %s [OPTIONS] FILE...\n%s%s%s", progname, "\
Tell the Emacs server to visit the specified files.\n\
Every FILE can be either just a FILENAME or [+LINE[:COLUMN]] FILENAME.\n\
\n\
The following OPTIONS are accepted:\n\
-V, --version		Just print version info and return\n\
-H, --help    		Print this usage information message\n\
-nw, -t, --tty 		Open a new Emacs frame on the current terminal\n\
-c, --create-frame    	Create a new frame instead of trying to\n\
			use the current Emacs frame\n\
", "\
-F ALIST, --frame-parameters=ALIST\n\
			Set the parameters of a new frame\n\
-e, --eval    		Evaluate the FILE arguments as ELisp expressions\n\
-n, --no-wait		Don't wait for the server to return\n\
-q, --quiet		Don't display messages on success\n\
-u, --suppress-output   Don't display return values from the server\n\
-d DISPLAY, --display=DISPLAY\n\
			Visit the file in the given display\n\
", "\
--parent-id=ID          Open in parent window ID, via XEmbed\n"
#ifndef NO_SOCKETS_IN_FILE_SYSTEM
"-s SOCKET, --socket-name=SOCKET\n\
			Set filename of the UNIX socket for communication\n"
#endif
"-f SERVER, --server-file=SERVER\n\
			Set filename of the TCP authentication file\n\
-a EDITOR, --alternate-editor=EDITOR\n\
			Editor to fallback to if the server is not running\n"
"			If EDITOR is the empty string, start Emacs in daemon\n\
			mode and try connecting again\n"
"-T PREFIX, --tramp=PREFIX\n\
                        PREFIX to prepend to filenames sent by emacsclient\n\
                        for locating files remotely via Tramp\n"
"\n\
Report bugs with M-x report-emacs-bug.\n");
  exit (EXIT_SUCCESS);
}

/* Try to run a different command, or --if no alternate editor is
   defined-- exit with an error code.
   Uses argv, but gets it from the global variable main_argv.  */

static _Noreturn void
fail (void)
{
  if (alternate_editor)
    {
      size_t extra_args_size = (main_argc - optind + 1) * sizeof (char *);
      size_t new_argv_size = extra_args_size;
      char **new_argv = xmalloc (new_argv_size);
      char *s = xstrdup (alternate_editor);
      ptrdiff_t toks = 0;

      /* Unpack alternate_editor's space-separated tokens into new_argv.  */
      for (char *tok = s; tok != NULL && *tok != '\0';)
        {
          /* Allocate new token.  */
          ++toks;
          new_argv = xrealloc (new_argv,
			       new_argv_size + toks * sizeof (char *));

          /* Skip leading delimiters, and set separator, skipping any
             opening quote.  */
          size_t skip = strspn (tok, " \"");
          tok += skip;
          char sep = (skip > 0 && tok[-1] == '"') ? '"' : ' ';

          /* Record start of token.  */
          new_argv[toks - 1] = tok;

          /* Find end of token and overwrite it with NUL.  */
          tok = strchr (tok, sep);
          if (tok != NULL)
            *tok++ = '\0';
        }

      /* Append main_argv arguments to new_argv.  */
      memcpy (&new_argv[toks], main_argv + optind, extra_args_size);

      execvp (*new_argv, new_argv);
      message (true, "%s: error executing alternate editor \"%s\"\n",
	       progname, alternate_editor);
    }
  exit (EXIT_FAILURE);
}


#if !defined (HAVE_SOCKETS) || !defined (HAVE_INET_SOCKETS)

int
main (int argc, char **argv)
{
  main_argc = argc;
  main_argv = argv;
  progname = argv[0];
  message (true, ("%s: Sorry, the Emacs server is supported only\n"
		  "on systems with Berkeley sockets.\n"),
	   argv[0]);
  fail ();
}

#else /* HAVE_SOCKETS && HAVE_INET_SOCKETS */

enum { AUTH_KEY_LENGTH = 64 };

/* Socket used to communicate with the Emacs server process.  */
static HSOCKET emacs_socket = 0;

static void
sock_err_message (const char *function_name)
{
# ifdef WINDOWSNT
  /* On Windows, the socket library was historically separate from the
     standard C library, so errors are handled differently.  */

  if (w32_window_app () && alternate_editor)
    return;

  char *msg = NULL;

  FormatMessage (FORMAT_MESSAGE_FROM_SYSTEM
                 | FORMAT_MESSAGE_ALLOCATE_BUFFER
                 | FORMAT_MESSAGE_ARGUMENT_ARRAY,
                 NULL, WSAGetLastError (), 0, (LPTSTR)&msg, 0, NULL);

  message (true, "%s: %s: %s\n", progname, function_name, msg);

  LocalFree (msg);
# else
  message (true, "%s: %s: %s\n", progname, function_name, strerror (errno));
# endif
}


/* Send to S the data in *DATA when either
   - the data's last byte is '\n', or
   - the buffer is full (but this shouldn't happen)
   Otherwise, just accumulate the data.  */
static void
send_to_emacs (HSOCKET s, const char *data)
{
  enum { SEND_BUFFER_SIZE = 4096 };

  /* Buffer to accumulate data to send in TCP connections.  */
  static char send_buffer[SEND_BUFFER_SIZE + 1];

  /* Fill pointer for the send buffer.  */
  static int sblen;

  for (ptrdiff_t dlen = strlen (data); dlen != 0; )
    {
      int part = min (dlen, SEND_BUFFER_SIZE - sblen);
      memcpy (&send_buffer[sblen], data, part);
      data += part;
      sblen += part;

      if (sblen == SEND_BUFFER_SIZE
	  || (0 < sblen && send_buffer[sblen - 1] == '\n'))
	{
	  int sent = send (s, send_buffer, sblen, 0);
	  if (sent < 0)
	    {
	      message (true, "%s: failed to send %d bytes to socket: %s\n",
		       progname, sblen, strerror (errno));
	      fail ();
	    }
	  if (sent != sblen)
	    memmove (send_buffer, &send_buffer[sent], sblen - sent);
	  sblen -= sent;
	}

      dlen -= part;
    }
}


/* In STR, insert a & before each &, each space, each newline, and
   any initial -.  Change spaces to underscores, too, so that the
   return value never contains a space.

   Does not change the string.  Outputs the result to S.  */
static void
quote_argument (HSOCKET s, const char *str)
{
  char *copy = xmalloc (strlen (str) * 2 + 1);
  char *q = copy;
  if (*str == '-')
    *q++ = '&', *q++ = *str++;
  for (; *str; str++)
    {
      char c = *str;
      if (c == ' ')
	*q++ = '&', c = '_';
      else if (c == '\n')
	*q++ = '&', c = 'n';
      else if (c == '&')
	*q++ = '&';
      *q++ = c;
    }
  *q = 0;

  send_to_emacs (s, copy);

  free (copy);
}


/* The inverse of quote_argument.  Remove quoting in string STR by
   modifying the addressed string in place.  Return STR.  */

static char *
unquote_argument (char *str)
{
  char const *p = str;
  char *q = str;
  char c;

  do
    {
      c = *p++;
      if (c == '&')
	{
	  c = *p++;
	  if (c == '_')
	    c = ' ';
	  else if (c == 'n')
	    c = '\n';
	}
      *q++ = c;
    }
  while (c);

  return str;
}


# ifdef WINDOWSNT
/* Wrapper to make WSACleanup a cdecl, as required by atexit.  */
void __cdecl close_winsock (void);
void __cdecl
close_winsock (void)
{
  WSACleanup ();
}

/* Initialize the WinSock2 library.  */
void initialize_sockets (void);
void
initialize_sockets (void)
{
  WSADATA wsaData;

  if (WSAStartup (MAKEWORD (2, 0), &wsaData))
    {
      message (true, "%s: error initializing WinSock2\n", progname);
      exit (EXIT_FAILURE);
    }

  atexit (close_winsock);
}
# endif /* WINDOWSNT */


/* If the home directory is HOME, return the configuration file with
   basename CONFIG_FILE.  Fail if there is no home directory or if the
   configuration file could not be opened.  */

static FILE *
open_config (char const *home, char const *config_file)
{
  if (!home)
    return NULL;
  ptrdiff_t homelen = strlen (home);
  static char const emacs_d_server[] = "/.emacs.d/server/";
  ptrdiff_t suffixsize = sizeof emacs_d_server + strlen (config_file);
  char *configname = xmalloc (homelen + suffixsize);
  strcpy (stpcpy (stpcpy (configname, home), emacs_d_server), config_file);

  FILE *config = fopen (configname, "rb");
  free (configname);
  return config;
}

/* Read the information needed to set up a TCP comm channel with
   the Emacs server: host, port, and authentication string.  */

static bool
get_server_config (const char *config_file, struct sockaddr_in *server,
		   char *authentication)
{
  char dotted[32];
  char *port;
  FILE *config;

  if (IS_ABSOLUTE_FILE_NAME (config_file))
    config = fopen (config_file, "rb");
  else
    {
      config = open_config (egetenv ("HOME"), config_file);
# ifdef WINDOWSNT
      if (!config)
	config = open_config (egetenv ("APPDATA"), config_file);
# endif
    }

  if (! config)
    return false;

  if (fgets (dotted, sizeof dotted, config)
      && (port = strchr (dotted, ':')))
    *port++ = '\0';
  else
    {
      message (true, "%s: invalid configuration info\n", progname);
      exit (EXIT_FAILURE);
    }

  memset (server, 0, sizeof *server);
  server->sin_family = AF_INET;
  server->sin_addr.s_addr = inet_addr (dotted);
  server->sin_port = htons (atoi (port));

  if (! fread (authentication, AUTH_KEY_LENGTH, 1, config))
    {
      message (true, "%s: cannot read authentication info\n", progname);
      exit (EXIT_FAILURE);
    }

  fclose (config);

  return true;
}

static HSOCKET
set_tcp_socket (const char *local_server_file)
{
  union {
    struct sockaddr_in in;
    struct sockaddr sa;
  } server;
  struct linger l_arg = { .l_onoff = 1, .l_linger = 1 };
  char auth_string[AUTH_KEY_LENGTH + 1];

  if (! get_server_config (local_server_file, &server.in, auth_string))
    return INVALID_SOCKET;

  if (server.in.sin_addr.s_addr != inet_addr ("127.0.0.1") && !quiet)
    message (false, "%s: connected to remote socket at %s\n",
	     progname, inet_ntoa (server.in.sin_addr));

  /* Open up an AF_INET socket.  */
  HSOCKET s = socket (AF_INET, SOCK_STREAM, IPPROTO_TCP);
  if (s < 0)
    {
      /* Since we have an alternate to try out, this is not an error
	 yet; popping out a modal dialog at this stage would make -a
	 option totally useless for emacsclientw -- the user will
	 still get an error message if the alternate editor fails.  */
      sock_err_message ("socket");
      return INVALID_SOCKET;
    }

  /* Set up the socket.  */
  if (connect (s, &server.sa, sizeof server.in) != 0)
    {
      sock_err_message ("connect");
      CLOSE_SOCKET (s);
      return INVALID_SOCKET;
    }

  setsockopt (s, SOL_SOCKET, SO_LINGER, &l_arg, sizeof l_arg);

  /* Send the authentication.  */
  auth_string[AUTH_KEY_LENGTH] = '\0';

  send_to_emacs (s, "-auth ");
  send_to_emacs (s, auth_string);
  send_to_emacs (s, " ");

  return s;
}


/* Return true if PREFIX is a prefix of STRING. */
static bool
strprefix (const char *prefix, const char *string)
{
  return !strncmp (prefix, string, strlen (prefix));
}

/* Get tty name and type.  If successful, store the type into
   *TTY_TYPE and the name into *TTY_NAME, and return true.
   Otherwise, fail if NOABORT is zero, or return false if NOABORT.  */

static bool
find_tty (const char **tty_type, const char **tty_name, bool noabort)
{
  const char *type = egetenv ("TERM");
  const char *name = ttyname (STDOUT_FILENO);

  if (!name)
    {
      if (noabort)
	return false;
      message (true, "%s: could not get terminal name\n", progname);
      fail ();
    }

  if (!type)
    {
      if (noabort)
	return false;
      message (true, "%s: please set the TERM variable to your terminal type\n",
	       progname);
      fail ();
    }

  const char *inside_emacs = egetenv ("INSIDE_EMACS");
  if (inside_emacs && strstr (inside_emacs, ",term:")
      && strprefix ("eterm", type))
    {
      if (noabort)
	return false;
      /* This causes nasty, MULTI_KBOARD-related input lockouts. */
      message (true, ("%s: opening a frame in an Emacs term buffer"
		      " is not supported\n"),
	       progname);
      fail ();
    }

  *tty_name = name;
  *tty_type = type;
  return true;
}


# ifndef NO_SOCKETS_IN_FILE_SYSTEM

/* Three possibilities:
  >0 - 'stat' failed with this errno value
  -1 - isn't owned by us
   0 - success: none of the above */

static int
socket_status (const char *name)
{
  struct stat statbfr;

  if (stat (name, &statbfr) != 0)
    return errno;

  if (statbfr.st_uid != geteuid ())
    return -1;

  return 0;
}


/* A signal handler that passes the signal to the Emacs process.
   Useful for SIGWINCH.  */

static void
pass_signal_to_emacs (int signalnum)
{
  int old_errno = errno;

  if (emacs_pid)
    kill (emacs_pid, signalnum);

  signal (signalnum, pass_signal_to_emacs);
  errno = old_errno;
}

/* Signal handler for SIGCONT; notify the Emacs process that it can
   now resume our tty frame.  */

static void
handle_sigcont (int signalnum)
{
  int old_errno = errno;
  pid_t pgrp = getpgrp ();
  pid_t tcpgrp = tcgetpgrp (STDOUT_FILENO);

  if (tcpgrp == pgrp)
    {
      /* We are in the foreground.  */
      send_to_emacs (emacs_socket, "-resume \n");
    }
  else if (0 <= tcpgrp && tty)
    {
      /* We are in the background; cancel the continue.  */
      kill (-pgrp, SIGTTIN);
    }

  signal (signalnum, handle_sigcont);
  errno = old_errno;
}

/* Signal handler for SIGTSTP; notify the Emacs process that we are
   going to sleep.  Normally the suspend is initiated by Emacs via
   server-handle-suspend-tty, but if the server gets out of sync with
   reality, we may get a SIGTSTP on C-z.  Handling this signal and
   notifying Emacs about it should get things under control again.  */

static void
handle_sigtstp (int signalnum)
{
  int old_errno = errno;
  sigset_t set;

  if (emacs_socket)
    send_to_emacs (emacs_socket, "-suspend \n");

  /* Unblock this signal and call the default handler by temporarily
     changing the handler and resignaling.  */
  sigprocmask (SIG_BLOCK, NULL, &set);
  sigdelset (&set, signalnum);
  signal (signalnum, SIG_DFL);
  raise (signalnum);
  sigprocmask (SIG_SETMASK, &set, NULL); /* Let's the above signal through. */
  signal (signalnum, handle_sigtstp);

  errno = old_errno;
}


/* Set up signal handlers before opening a frame on the current tty.  */

static void
init_signals (void)
{
  /* Don't pass SIGINT and SIGQUIT to Emacs, because it has no way of
     deciding which terminal the signal came from.  C-g is now a
     normal input event on secondary terminals.  */
  signal (SIGWINCH, pass_signal_to_emacs);
  signal (SIGCONT, handle_sigcont);
  signal (SIGTSTP, handle_sigtstp);
  signal (SIGTTOU, handle_sigtstp);
}

/* Create a local socket and connect it to Emacs.  */

static HSOCKET
set_local_socket (const char *local_socket_name)
{
  union {
    struct sockaddr_un un;
    struct sockaddr sa;
  } server = {{ .sun_family = AF_UNIX }};

  HSOCKET s = socket (AF_UNIX, SOCK_STREAM, 0);
  if (s < 0)
    {
      message (true, "%s: socket: %s\n", progname, strerror (errno));
      return INVALID_SOCKET;
    }

  char const *server_name = local_socket_name;
  char const *tmpdir = NULL;
  char *tmpdir_storage = NULL;
  char *socket_name_storage = NULL;
  static char const subdir_format[] = "/emacs%"PRIuMAX"/";
  int subdir_size_bound = (sizeof subdir_format - sizeof "%"PRIuMAX
			   + INT_STRLEN_BOUND (uid_t) + 1);

  if (! (strchr (local_socket_name, '/')
	 || (ISSLASH ('\\') && strchr (local_socket_name, '\\'))))
    {
      /* socket_name is a file name component.  */
      uintmax_t uid = geteuid ();
      tmpdir = egetenv ("TMPDIR");
      if (!tmpdir)
	{
#  ifdef DARWIN_OS
#   ifndef _CS_DARWIN_USER_TEMP_DIR
#    define _CS_DARWIN_USER_TEMP_DIR 65537
#   endif
	  size_t n = confstr (_CS_DARWIN_USER_TEMP_DIR, NULL, 0);
	  if (n > 0)
	    {
	      tmpdir = tmpdir_storage = xmalloc (n);
	      confstr (_CS_DARWIN_USER_TEMP_DIR, tmpdir_storage, n);
	    }
	  else
#  endif
	    tmpdir = "/tmp";
	}
      socket_name_storage =
	xmalloc (strlen (tmpdir) + strlen (server_name) + subdir_size_bound);
      char *z = stpcpy (socket_name_storage, tmpdir);
      strcpy (z + sprintf (z, subdir_format, uid), server_name);
      local_socket_name = socket_name_storage;
    }

  if (strlen (local_socket_name) < sizeof server.un.sun_path)
    strcpy (server.un.sun_path, local_socket_name);
  else
    {
      message (true, "%s: socket-name %s too long\n",
	       progname, local_socket_name);
      fail ();
    }

  /* See if the socket exists, and if it's owned by us. */
  int sock_status = socket_status (server.un.sun_path);
  if (sock_status && tmpdir)
    {
      /* Failing that, see if LOGNAME or USER exist and differ from
	 our euid.  If so, look for a socket based on the UID
	 associated with the name.  This is reminiscent of the logic
	 that init_editfns uses to set the global Vuser_full_name.  */

      char const *user_name = egetenv ("LOGNAME");

      if (!user_name)
	user_name = egetenv ("USER");

      if (user_name)
	{
	  struct passwd *pw = getpwnam (user_name);

	  if (pw && (pw->pw_uid != geteuid ()))
	    {
	      /* We're running under su, apparently. */
	      uintmax_t uid = pw->pw_uid;
	      char *user_socket_name
		= xmalloc (strlen (tmpdir) + strlen (server_name)
			   + subdir_size_bound);
	      char *z = stpcpy (user_socket_name, tmpdir);
	      strcpy (z + sprintf (z, subdir_format, uid), server_name);

	      if (strlen (user_socket_name) < sizeof server.un.sun_path)
		strcpy (server.un.sun_path, user_socket_name);
	      else
		{
		  message (true, "%s: socket-name %s too long\n",
			   progname, user_socket_name);
		  exit (EXIT_FAILURE);
		}
	      free (user_socket_name);

	      sock_status = socket_status (server.un.sun_path);
	    }
	}
    }

  free (socket_name_storage);
  free (tmpdir_storage);

  switch (sock_status)
    {
    case -1:
      /* There's a socket, but it isn't owned by us.  */
      message (true, "%s: Invalid socket owner\n", progname);
      break;

    case 0:
      if (connect (s, &server.sa, sizeof server.un) == 0)
	return s;
      message (true, "%s: connect: %s\n", progname, strerror (errno));
      break;

    default:
      /* 'stat' failed.  */
      if (sock_status == ENOENT)
	message (true,
		 ("%s: can't find socket; have you started the server?\n"
		  "%s: To start the server in Emacs,"
		  " type \"M-x server-start\".\n"),
		 progname, progname);
      else
	message (true, "%s: can't stat %s: %s\n",
		 progname, server.un.sun_path, strerror (sock_status));
      break;
    }

  CLOSE_SOCKET (s);
  return INVALID_SOCKET;
}
# endif /* ! NO_SOCKETS_IN_FILE_SYSTEM */

static HSOCKET
set_socket (bool no_exit_if_error)
{
  HSOCKET s;
  const char *local_server_file = server_file;

  INITIALIZE ();

# ifndef NO_SOCKETS_IN_FILE_SYSTEM
  /* Explicit --socket-name argument.  */
  if (!socket_name)
    socket_name = egetenv ("EMACS_SOCKET_NAME");

  if (socket_name)
    {
      s = set_local_socket (socket_name);
      if (s != INVALID_SOCKET || no_exit_if_error)
	return s;
      message (true, "%s: error accessing socket \"%s\"\n",
	       progname, socket_name);
      exit (EXIT_FAILURE);
    }
# endif

  /* Explicit --server-file arg or EMACS_SERVER_FILE variable.  */
  if (!local_server_file)
    local_server_file = egetenv ("EMACS_SERVER_FILE");

  if (local_server_file)
    {
      s = set_tcp_socket (local_server_file);
      if (s != INVALID_SOCKET || no_exit_if_error)
	return s;

      message (true, "%s: error accessing server file \"%s\"\n",
	       progname, local_server_file);
      exit (EXIT_FAILURE);
    }

# ifndef NO_SOCKETS_IN_FILE_SYSTEM
  /* Implicit local socket.  */
  s = set_local_socket ("server");
  if (s != INVALID_SOCKET)
    return s;
# endif

  /* Implicit server file.  */
  s = set_tcp_socket ("server");
  if (s != INVALID_SOCKET || no_exit_if_error)
    return s;

  /* No implicit or explicit socket, and no alternate editor.  */
  message (true, "%s: No socket or alternate editor.  Please use:\n\n"
# ifndef NO_SOCKETS_IN_FILE_SYSTEM
"\t--socket-name\n"
# endif
"\t--server-file      (or environment variable EMACS_SERVER_FILE)\n\
\t--alternate-editor (or environment variable ALTERNATE_EDITOR)\n",
           progname);
  exit (EXIT_FAILURE);
}

# ifdef HAVE_NTGUI
FARPROC set_fg;  /* Pointer to AllowSetForegroundWindow.  */
FARPROC get_wc;  /* Pointer to RealGetWindowClassA.  */

void w32_set_user_model_id (void);

void
w32_set_user_model_id (void)
{
  HMODULE shell;
  HRESULT (WINAPI * set_user_model) (const wchar_t * id);

  /* On Windows 7 and later, we need to set the user model ID
     to associate emacsclient launched files with Emacs frames
     in the UI.  */
  shell = LoadLibrary ("shell32.dll");
  if (shell)
    {
      set_user_model
	= (void *) GetProcAddress (shell,
				   "SetCurrentProcessExplicitAppUserModelID");
      /* If the function is defined, then we are running on Windows 7
	 or newer, and the UI uses this to group related windows
	 together.  Since emacs, runemacs, emacsclient are related, we
	 want them grouped even though the executables are different,
	 so we need to set a consistent ID between them.  */
      if (set_user_model)
	set_user_model (L"GNU.Emacs");

      FreeLibrary (shell);
    }
}

BOOL CALLBACK w32_find_emacs_process (HWND, LPARAM);

BOOL CALLBACK
w32_find_emacs_process (HWND hWnd, LPARAM lParam)
{
  DWORD pid;
  char class[6];

  /* Reject any window not of class "Emacs".  */
  if (! get_wc (hWnd, class, sizeof (class))
      || strcmp (class, "Emacs"))
    return TRUE;

  /* We only need the process id, not the thread id.  */
  (void) GetWindowThreadProcessId (hWnd, &pid);

  /* Not the one we're looking for.  */
  if (pid != (DWORD) emacs_pid) return TRUE;

  /* OK, let's raise it.  */
  set_fg (emacs_pid);

  /* Stop enumeration.  */
  return FALSE;
}

/* Search for a window of class "Emacs" and owned by a process with
   process id = emacs_pid.  If found, allow it to grab the focus.  */
void w32_give_focus (void);

void
w32_give_focus (void)
{
  HANDLE user32;

  /* It shouldn't happen when dealing with TCP sockets.  */
  if (!emacs_pid) return;

  user32 = GetModuleHandle ("user32.dll");

  if (!user32)
    return;

  /* Modern Windows restrict which processes can set the foreground window.
     emacsclient can allow Emacs to grab the focus by calling the function
     AllowSetForegroundWindow.  Unfortunately, older Windows (W95, W98 and
     NT) lack this function, so we have to check its availability.  */
  if ((set_fg = GetProcAddress (user32, "AllowSetForegroundWindow"))
      && (get_wc = GetProcAddress (user32, "RealGetWindowClassA")))
    EnumWindows (w32_find_emacs_process, (LPARAM) 0);
}
# endif /* HAVE_NTGUI */

/* Start the emacs daemon and try to connect to it.  */

static void
start_daemon_and_retry_set_socket (void)
{
# ifndef WINDOWSNT
  pid_t dpid;
  int status;

  dpid = fork ();

  if (dpid > 0)
    {
      pid_t w = waitpid (dpid, &status, WUNTRACED | WCONTINUED);

      if (w < 0 || !WIFEXITED (status) || WEXITSTATUS (status))
	{
	  message (true, "Error: Could not start the Emacs daemon\n");
	  exit (EXIT_FAILURE);
	}

      /* Try connecting, the daemon should have started by now.  */
      message (true,
	       "Emacs daemon should have started, trying to connect again\n");

      if ((emacs_socket = set_socket (1)) == INVALID_SOCKET)
	{
	  message (true, ("Error: Cannot connect "
			  "even after starting the Emacs daemon\n"));
	  exit (EXIT_FAILURE);
	}
    }
  else if (dpid < 0)
    {
      fprintf (stderr, "Error: Cannot fork!\n");
      exit (EXIT_FAILURE);
    }
  else
    {
      char emacs[] = "emacs";
      char daemon_option[] = "--daemon";
      char *d_argv[3];
      d_argv[0] = emacs;
      d_argv[1] = daemon_option;
      d_argv[2] = 0;
#ifndef NO_SOCKETS_IN_FILE_SYSTEM
      if (socket_name != NULL)
	{
	  /* Pass  --daemon=socket_name as argument.  */
	  const char *deq = "--daemon=";
	  char *daemon_arg = xmalloc (strlen (deq)
				      + strlen (socket_name) + 1);
	  strcpy (stpcpy (daemon_arg, deq), socket_name);
	  d_argv[1] = daemon_arg;
	}
#endif
      execvp ("emacs", d_argv);
      message (true, "%s: error starting emacs daemon\n", progname);
    }
# else  /* WINDOWSNT */
  DWORD wait_result;
  HANDLE w32_daemon_event;
  STARTUPINFO si;
  PROCESS_INFORMATION pi;

  ZeroMemory (&si, sizeof si);
  si.cb = sizeof si;
  ZeroMemory (&pi, sizeof pi);

  /* We start Emacs in daemon mode, and then wait for it to signal us
     it is ready to accept client connections, by asserting an event
     whose name is known to the daemon (defined by nt/inc/ms-w32.h).  */

  if (!CreateProcess (NULL, (LPSTR)"emacs --daemon", NULL, NULL, FALSE,
                      CREATE_NO_WINDOW, NULL, NULL, &si, &pi))
    {
      char* msg = NULL;

      FormatMessage (FORMAT_MESSAGE_FROM_SYSTEM
		     | FORMAT_MESSAGE_ALLOCATE_BUFFER
		     | FORMAT_MESSAGE_ARGUMENT_ARRAY,
		     NULL, GetLastError (), 0, (LPTSTR)&msg, 0, NULL);
      message (true, "%s: error starting emacs daemon (%s)\n", progname, msg);
      exit (EXIT_FAILURE);
    }

  w32_daemon_event = CreateEvent (NULL, TRUE, FALSE, W32_DAEMON_EVENT);
  if (w32_daemon_event == NULL)
    {
      message (true, "Couldn't create Windows daemon event");
      exit (EXIT_FAILURE);
    }
  if ((wait_result = WaitForSingleObject (w32_daemon_event, INFINITE))
      != WAIT_OBJECT_0)
    {
      const char *msg = NULL;

      switch (wait_result)
	{
	case WAIT_ABANDONED:
	  msg = "The daemon exited unexpectedly";
	  break;
	case WAIT_TIMEOUT:
	  /* Can't happen due to INFINITE.  */
	default:
	case WAIT_FAILED:
	  FormatMessage (FORMAT_MESSAGE_FROM_SYSTEM
			 | FORMAT_MESSAGE_ALLOCATE_BUFFER
			 | FORMAT_MESSAGE_ARGUMENT_ARRAY,
			 NULL, GetLastError (), 0, (LPTSTR)&msg, 0, NULL);
	  break;
	}
      message (true, "Error: Could not start the Emacs daemon: %s\n", msg);
      exit (EXIT_FAILURE);
    }
  CloseHandle (w32_daemon_event);

  /* Try connecting, the daemon should have started by now.  */
  /* It's just a progress message, so don't pop a dialog if this is
     emacsclientw.  */
  if (!w32_window_app ())
    message (true,
	     "Emacs daemon should have started, trying to connect again\n");
  if ((emacs_socket = set_socket (1)) == INVALID_SOCKET)
    {
      message (true,
	       "Error: Cannot connect even after starting the Emacs daemon\n");
      exit (EXIT_FAILURE);
    }
# endif	/* WINDOWSNT */
}

int
main (int argc, char **argv)
{
  int rl = 0;
  bool skiplf = true;
  char string[BUFSIZ+1];
  int exit_status = EXIT_SUCCESS;

  main_argc = argc;
  main_argv = argv;
  progname = argv[0];

#ifdef HAVE_NTGUI
  /* On Windows 7 and later, we need to explicitly associate
     emacsclient with emacs so the UI behaves sensibly.  This
     association does no harm if we're not actually connecting to an
     Emacs using a window display.  */
  w32_set_user_model_id ();
#endif /* HAVE_NTGUI */

  /* Process options.  */
  decode_options (argc, argv);

  if (! (optind < argc || eval || create_frame))
    {
      message (true, ("%s: file name or argument required\n"
		      "Try '%s --help' for more information\n"),
	       progname, progname);
      exit (EXIT_FAILURE);
    }

#ifndef WINDOWSNT
  if (tty)
    {
      pid_t pgrp = getpgrp ();
      pid_t tcpgrp = tcgetpgrp (STDOUT_FILENO);
      if (0 <= tcpgrp && tcpgrp != pgrp)
	kill (-pgrp, SIGTTIN);
    }
#endif /* !WINDOWSNT */

  /* If alternate_editor is the empty string, start the emacs daemon
     in case of failure to connect.  */
  bool start_daemon_if_needed = alternate_editor && !alternate_editor[0];

  emacs_socket = set_socket (alternate_editor || start_daemon_if_needed);
  if (emacs_socket == INVALID_SOCKET)
    {
      if (! start_daemon_if_needed)
	fail ();

      start_daemon_and_retry_set_socket ();
    }

  char *cwd = get_current_dir_name ();
  if (cwd == 0)
    {
      message (true, "%s: %s\n", progname,
	       "Cannot get current working directory");
      fail ();
    }

# ifdef HAVE_NTGUI
  if (display && !strcmp (display, "w32"))
  w32_give_focus ();
# endif /* HAVE_NTGUI */

  /* Send over our environment and current directory. */
  if (create_frame)
    {
      for (char *const *e = environ; *e; e++)
        {
          send_to_emacs (emacs_socket, "-env ");
          quote_argument (emacs_socket, *e);
          send_to_emacs (emacs_socket, " ");
        }
    }
  send_to_emacs (emacs_socket, "-dir ");
  if (tramp_prefix)
    quote_argument (emacs_socket, tramp_prefix);
  quote_argument (emacs_socket, cwd);
  free (cwd);
  send_to_emacs (emacs_socket, "/");
  send_to_emacs (emacs_socket, " ");

 retry:
  if (nowait)
    send_to_emacs (emacs_socket, "-nowait ");

  if (!create_frame)
    send_to_emacs (emacs_socket, "-current-frame ");

  if (display)
    {
      send_to_emacs (emacs_socket, "-display ");
      quote_argument (emacs_socket, display);
      send_to_emacs (emacs_socket, " ");
    }

  if (parent_id)
    {
      send_to_emacs (emacs_socket, "-parent-id ");
      quote_argument (emacs_socket, parent_id);
      send_to_emacs (emacs_socket, " ");
    }

  if (frame_parameters && create_frame)
    {
      send_to_emacs (emacs_socket, "-frame-parameters ");
      quote_argument (emacs_socket, frame_parameters);
      send_to_emacs (emacs_socket, " ");
    }

  /* Unless we are certain we don't want to occupy the tty, send our
     tty information to Emacs.  For example, in daemon mode Emacs may
     need to occupy this tty if no other frame is available.  */
  if (create_frame || !eval)
    {
      const char *tty_type, *tty_name;

      if (find_tty (&tty_type, &tty_name, !tty))
	{
# ifndef NO_SOCKETS_IN_FILE_SYSTEM
	  init_signals ();
# endif
	  send_to_emacs (emacs_socket, "-tty ");
	  quote_argument (emacs_socket, tty_name);
	  send_to_emacs (emacs_socket, " ");
	  quote_argument (emacs_socket, tty_type);
	  send_to_emacs (emacs_socket, " ");
	}
    }

  if (create_frame && !tty)
    send_to_emacs (emacs_socket, "-window-system ");

  if (optind < argc)
    {
      for (int i = optind; i < argc; i++)
	{

	  if (eval)
            {
              /* Don't prepend cwd or anything like that.  */
              send_to_emacs (emacs_socket, "-eval ");
              quote_argument (emacs_socket, argv[i]);
              send_to_emacs (emacs_socket, " ");
              continue;
            }

	  char *p = argv[i];
	  if (*p == '+')
            {
	      unsigned char c;
	      do
		c = *++p;
	      while (isdigit (c) || c == ':');

	      if (c == 0)
                {
                  send_to_emacs (emacs_socket, "-position ");
                  quote_argument (emacs_socket, argv[i]);
                  send_to_emacs (emacs_socket, " ");
                  continue;
                }
            }
# ifdef WINDOWSNT
	  else if (! IS_ABSOLUTE_FILE_NAME (argv[i])
		   && (isalpha (argv[i][0]) && argv[i][1] == ':'))
	    /* Windows can have a different default directory for each
	       drive, so the cwd passed via "-dir" is not sufficient
	       to account for that.
	       If the user uses <drive>:<relpath>, we hence need to be
	       careful to expand <relpath> with the default directory
	       corresponding to <drive>.  */
	    {
	      char *filename = xmalloc (MAX_PATH);
	      DWORD size;

	      size = GetFullPathName (argv[i], MAX_PATH, filename, NULL);
	      if (size > 0 && size < MAX_PATH)
		argv[i] = filename;
	      else
		free (filename);
	    }
# endif

          send_to_emacs (emacs_socket, "-file ");
	  if (tramp_prefix && IS_ABSOLUTE_FILE_NAME (argv[i]))
	    quote_argument (emacs_socket, tramp_prefix);
          quote_argument (emacs_socket, argv[i]);
          send_to_emacs (emacs_socket, " ");
        }
    }
  else if (eval)
    {
      /* Read expressions interactively.  */
      while (fgets (string, BUFSIZ, stdin))
	{
	  send_to_emacs (emacs_socket, "-eval ");
	  quote_argument (emacs_socket, string);
	}
      send_to_emacs (emacs_socket, " ");
    }

  send_to_emacs (emacs_socket, "\n");

  /* Wait for an answer. */
  if (!eval && !tty && !nowait && !quiet)
    {
      printf ("Waiting for Emacs...");
      skiplf = false;
    }
  fflush (stdout);
  while (fdatasync (STDOUT_FILENO) != 0 && errno == EINTR)
    continue;

  /* Now, wait for an answer and print any messages.  */
  while (exit_status == EXIT_SUCCESS)
    {
      do
        {
          errno = 0;
          rl = recv (emacs_socket, string, BUFSIZ, 0);
        }
      /* If we receive a signal (e.g. SIGWINCH, which we pass
	 through to Emacs), on some OSes we get EINTR and must retry. */
      while (rl < 0 && errno == EINTR);

      if (rl <= 0)
        break;

      string[rl] = '\0';

      /* Loop over all NL-terminated messages.  */
      char *p = string;
      for (char *end_p = p; end_p && *end_p != '\0'; p = end_p)
	{
	  end_p = strchr (p, '\n');
	  if (end_p != NULL)
	    *end_p++ = '\0';

          if (strprefix ("-emacs-pid ", p))
            {
              /* -emacs-pid PID: The process id of the Emacs process. */
	      emacs_pid = strtoumax (p + strlen ("-emacs-pid"), NULL, 10);
            }
          else if (strprefix ("-window-system-unsupported ", p))
            {
              /* -window-system-unsupported: Emacs was compiled without support
                 for whatever window system we tried.  Try the alternate
                 display, or, failing that, try the terminal.  */
              if (alt_display)
                {
                  display = alt_display;
                  alt_display = NULL;
                }
              else
                {
                  nowait = false;
                  tty = true;
                }

              goto retry;
            }
          else if (strprefix ("-print ", p))
            {
              /* -print STRING: Print STRING on the terminal. */
	      if (!suppress_output)
		{
		  char *str = unquote_argument (p + strlen ("-print "));
		  printf (&"\n%s"[skiplf], str);
		  if (str[0])
		    skiplf = str[strlen (str) - 1] == '\n';
		}
	    }
          else if (strprefix ("-print-nonl ", p))
            {
              /* -print-nonl STRING: Print STRING on the terminal.
                 Used to continue a preceding -print command.  */
	      if (!suppress_output)
		{
		  char *str = unquote_argument (p + strlen ("-print-nonl "));
		  printf ("%s", str);
		  if (str[0])
		    skiplf = str[strlen (str) - 1] == '\n';
		}
            }
          else if (strprefix ("-error ", p))
            {
              /* -error DESCRIPTION: Signal an error on the terminal. */
              char *str = unquote_argument (p + strlen ("-error "));
              if (!skiplf)
                printf ("\n");
              fprintf (stderr, "*ERROR*: %s", str);
              if (str[0])
	        skiplf = str[strlen (str) - 1] == '\n';
              exit_status = EXIT_FAILURE;
            }
# ifdef SIGSTOP
	  else if (strprefix ("-suspend ", p))
	    {
	      /* -suspend: Suspend this terminal, i.e., stop the process. */
	      if (!skiplf)
		printf ("\n");
	      skiplf = true;
	      kill (0, SIGSTOP);
	    }
# endif
	  else
	    {
	      /* Unknown command. */
	      printf (&"\n*ERROR*: Unknown message: %s\n"[skiplf], p);
	      skiplf = true;
	    }
	}
    }

  if (!skiplf)
    printf ("\n");
  fflush (stdout);
  while (fdatasync (STDOUT_FILENO) != 0 && errno == EINTR)
    continue;

  if (rl < 0)
    exit_status = EXIT_FAILURE;

  CLOSE_SOCKET (emacs_socket);
  return exit_status;
}

#endif /* HAVE_SOCKETS && HAVE_INET_SOCKETS */