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1 @\input texinfo @c -*-texinfo-*-
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2 settitle Notes about emacs Term mode
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3 @setfilename ../info/term.info
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4
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5 @titlepage
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6 @sp 6
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7 @center @titlefont(Notes about Emacs TERM Mode)
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8 @end titlepage
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9
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10 @ifinfo
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11 @c @format
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12 @c START-INFO-DIR-ENTRY
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13 @c * term mode:: Emacs terminal emulator mode.
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14 @c END-INFO-DIR-ENTRY
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15 @c @end format
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16
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17 @node Top, , (DIR)
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18 @top Terminal emulator mode
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19 @end ifinfo
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20
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21 This is some notes about the term Emacs mode.
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22
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23 @menu
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24 * term mode::
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25 @end menu
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26
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27 @node term mode
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28 @chapter Term Mode
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29
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30 @menu
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31 * Overview::
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32 * Connecting to remote computers::
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33 * Paging::
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34 * Terminal escapes::
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35 @end menu
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36
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37 The @code{term} package includes the major modes @code{term},
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38 @code{shell}, and @code{gud} (for running gbd or another debugger).
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39 It is a replacement for the comint mode of Emacs 19,
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40 as well as shell, gdb, terminal, and telnet modes.
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41 The package works best with recent releases of Emacs 19,
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42 but will also work reasonably well with Emacs 18 as well as Lucid Emacs 19.
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43
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44 The file @code{nshell.el} is a wrapper to use unless term mode
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45 is built into Emacs. If works around some of the missing
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46 in older Emacs versions.
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47 To use it, edit the paths in @code{nshell.el}, appropriately,
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48 and then @code{M-x load-file nshell.el RET}.
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49 This will also load in replacement shell and gud modes.
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50
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51 @node Overview
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52 @section Overview
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53
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54 The @code{term} mode is used to control a program (an "inferior process").
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55 It sends most keyboard input characters to the program,
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56 and displays output from the program in the buffer.
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57 This is similar to the traditional comint mode, and
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58 modes derived from it (such as shell and gdb modes).
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59 You can do with the new term-based shell the same sort
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60 of things you could do with the old shell mode,
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61 using more or less the same interface. However, the
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62 new mode is more flexible, and works somewhat differently.
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63
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64 @menu
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65 * Output from the inferior::
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66 * subbuffer:: The sub-buffer
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67 * altsubbuffer:: The alternate sub-buffer
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68 * Input to the inferior::
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69 @end menu
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70
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71 @node Output from the inferior
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72 @subsection Output from the inferior
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73
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74 In typical usage, output from the inferior is
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75 added to the end of the buffer. If needed, the window
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76 will be scrolled, just like a regular terminal.
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77 (Only one line at a time will be scrolled, just like
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78 regular terminals, and in contrast to the old shell mode.)
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79 Thus the buffer becomes a log of your interaction with the
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80 inferior, just like the old shell mode.
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81
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82 Like a real terminal, term maintains a "cursor position."
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83 This is the @code{process-mark} of the inferior process.
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84 If the process-mark is not at the end of the buffer, output from
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85 the inferior will overwrite existing text in the buffer.
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86 This is like a real terminal, but unlike the old shell mode
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87 (which inserts the output, instead of overwriting).
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88
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89 Some programs (such as Emacs itself) need to control the
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90 appearance on the screen in detail. They do this by
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91 sending special control codes. The exact control
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92 codes needed from terminal to terminal, but nowadays
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93 most terminals and terminal emulators (including xterm)
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94 understand the so-called "ANSI escape sequences" (first
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95 popularized by the Digital's VT100 family of terminal).
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96 The term mode also understands these escape sequences,
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97 and for each control code does the appropriate thing
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98 to change the buffer so that the appearance of the window
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99 will match what it would be on a real terminal.
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100 (In contrast, the old shell mode doesn't handle
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101 terminal control codes at all.)
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102
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103 See <...> for the specific control codes.
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104
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105 @node subbuffer
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106 @subsection The sub-buffer
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107
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108 A program that talks to terminal expects the terminal to have a fixed size.
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109 If the program is talking a terminal emulator program such as @code{xterm},
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110 that size can be changed (if the xterm window is re-sized), but programs
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111 still assume a logical terminal that has a fixed size independent
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112 of the amount of output transmitted by the programs.
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113
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114 To programs that use it, the Emacs terminal emulator acts as if it
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115 too has a fixed size. The @dfn{sub-buffer} is the part of a @code{term}-mode
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116 buffer that corresponds to a "normal" terminal. Most of the time
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117 (unless you explicitly scroll the window displaying the buffer),
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118 the sub-buffer is the part of the buffer that is displayed in a window.
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119
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120 The sub-buffer is defined in terms of three buffer-local-variable:
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121
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122 @defvar term-height
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123 The height of the sub-buffer, in screen lines.
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124 @end defvar
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125
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126 @defvar term-width
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127 The width of the sub-buffer, in screen columns.
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128 @end defvar
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129
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130 @defvar term-home-marker
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131 The "home" position, that is the top left corner of the sub-buffer.
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132 @end defvar
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133
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134 The sub-buffer is assumed to be the end part of the buffer;
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135 the @code{term-home-marker} should never be more than
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136 @code{term-height} screen lines from the end of the buffer.
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137
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138 @node altsubbuffer
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139 @subsection The alternate sub-buffer
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140
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141 When a "graphical" program finishes, it is nice to
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142 restore the screen state to what it was before the program started.
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143 Many people are used to this behavior from @code{xterm}, and
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144 its also offered by the @code{term} emulator.
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145
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146 @defun term-switch-to-alternate-sub-buffer set
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147 If @var{set} is true, and we're not already using the alternate sub-buffer,
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148 switch to it. What this means is that the @code{term-home-marker}
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149 is saved (in the variable @code{term-saved-home-marker}), and the
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150 @code{term-home-marker} is set to the end of the buffer.
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151
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152 If @var{set} is false and we're using the alternate sub-buffer,
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153 switch back to the saved sub-buffer. What this means is that the
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154 (current, alternate) sub-buffer is deleted (using
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155 @code{(delete-region term-home-marker (point-max))}), and then the
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156 @code{term-home-marker} is restored (from @code{term-saved-home-marker}).
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157 @end defun
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158
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159 @node Input to the inferior
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160 @subsection Input to the inferior
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161
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162 Characters typed by the user are sent to the inferior.
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163 How this is done depends on whether the @code{term} buffer
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164 is in "character" mode or "line" mode.
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165 (A @code{term} buffer can also be in "pager" mode.
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166 This is discussed <later>.)
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167 Which of these is currently active is specified in the mode line.
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168 The difference between them is the key-bindings available.
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169
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170 In character mode, one character (by default @key{C-c}) is special,
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171 and is a prefix for various commands. All other characters are
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172 sent directly to the inferior process, with no interpretation by Emacs.
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173 Character mode looks and feels like a real terminal, or a conventional
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174 terminal emulator such as xterm.
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175
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176 In line mode, key commands mostly have standard Emacs actions.
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177 Regulars characters insert themselves into the buffer.
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178 When return is typed, the entire current line of the buffer
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179 (except possibly the prompt) is sent to the inferior process.
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180 Line mode is basically the original shell mode from earlier Emacs versions.
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181
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182 To switch from line mode to character mode type @kbd{C-c c}.
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183 To switch from character mode to line mode type @kbd{C-c l}.
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184
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185 In either mode, "echoing" of user input is handled by the inferior.
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186 Therefor, in line mode after an input line at the end of the buffer
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187 is sent to the inferior, it is deleted from the buffer.
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188 This is so that the inferior can echo the input, if it wishes
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189 (which it normally does).
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190
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191 @node Connecting to remote computers
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192 @section Connecting to remote computers
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193
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194 If you want to login to a remove computer, you can do that just as
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195 you would expect, using whatever commands you would normally use.
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196
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197 (This is worth emphasizing, because earlier versions of @code{shell}
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198 mode would not work properly if you tried to log in to some other
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199 computer, because of the way echoing was handled. That is why
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200 there was a separate @code{telnet} mode to partially compensate for
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201 these problems. The @code{telnet} mode is no longer needed, and
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202 is basically obsolete.)
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203
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204 A program that asks you for a password will normally suppress
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205 echoing of the password, so the password will not show up in the buffer.
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206 This will happen just as if you were using a real terminal, if
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207 the buffer is in char mode. If it is in line mode, the password
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208 will be temporarily visible, but will be erased when you hit return.
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209 (This happens automatically; there is no special password processing.)
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210
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211 When you log in to a different machine, you need to specify the
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212 type of terminal your using. If you are talking to a Bourne-compatible
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213 shell, and your system understands the @code{TERMCAP} variable,
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214 you can use the command @kbd{M-x shell-send-termcap}, which
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215 sends a string specifying the terminal type and size.
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216 (This command is also useful after the window has changed size.)
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217
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218 If you need to specify the terminal type manually, you can try the
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219 terminal types "ansi" or "vt100".
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220
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221 You can of course run gdb on that remote computer. One useful
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222 trick: If you invoke gdb with the @code{--fullname} option,
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223 it will send special commands to Emacs that will cause Emacs to
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224 pop up the source files you're debugging. This will work
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225 whether or not gdb is running on a different computer than Emacs,
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226 assuming can access the source files specified by gdb.
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227
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228 @node Paging
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229 @section Paging
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230
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231 When the pager is enabled, Emacs will "pause" after each screenful
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232 of output (since the last input sent to the inferior).
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233 It will enter "pager" mode, which feels a lot like the "more"
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234 program: Typing a space requests another screenful of output.
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235 Other commands request more or less output, or scroll backwards
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236 in the @code{term} buffer. In pager mode, type @kbd{h} or @kbd{?}
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237 to display a help message listing all the available pager mode commands.
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238
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239 In either character or line mode, type @kbd{C-c p} to enable paging,
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240 and @kbd{C-c D} to disable it.
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241
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242 @node Terminal escapes
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243 @section Terminal Escape sequences
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244
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245 A program that does "graphics" on a terminal controls the
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246 terminal by sending strings called @dfn{terminal escape sequences}
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247 that the terminal (or terminal emulator) interprets as special commands.
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248 The @code{term} mode includes a terminal emulator that understands
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249 standard ANSI escape sequences, originally popularized by VT100 terminals,
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250 and now used by the @code{xterm} program and most modern terminal
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251 emulator software.
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252
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253 @menu
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254 * Cursor motion:: Escape sequences to move the cursor
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255 * Erasing:: Escape commands for erasing text
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256 * Inserting and deleting:: Escape sequences to insert and delete text
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257 * Scrolling:: Escape sequences to scroll part of the visible window
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258 * Command hook::
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259 * Miscellaneous escapes::
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260 @end menu
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261
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262 printing chars
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263
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264 tab
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265
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266 LF
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267
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268 @node Cursor motion
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269 @subsection Escape sequences to move the cursor
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270
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271 @table @kbd
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272 @item RETURN
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273 Moves to the beginning of the current screen line.
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274
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275 @item C-b
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276 Moves backwards one column. (Tabs are broken up if needed.)
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277 @comment Line wrap FIXME
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278
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279 @item Esc [ R ; C H
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280 Move to screen row R, screen column C, where (R=1) is the top row,
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281 and (C=1) is the leftmost column. Defaults are R=1 and C=1.
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282
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283 @item Esc [ N A
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284 Move N (default 1) screen lines up.
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285 @item Esc [ N B
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286 Move N (default 1) screen lines down.
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287 @item Esc [ N C
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288 Move N (default 1) columns right.
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289 @item Esc [ N D
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290 Move N (default 1) columns left.
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291 @end table
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292
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293 @node Erasing
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294 @subsection Escape commands for erasing text
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295
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296 These commands "erase" part of the sub-buffer.
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297 Erasing means replacing by white space; it is not the same as deleting.
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298 The relative screen positions of things that are not erased remain
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299 unchanged with each other, as does the relative cursor position.
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300
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301 @table @kbd
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302 @item E [ J
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303 Erase from cursor to end of screen.
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304 @item E [ 0 J
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305 Same as E [ J.
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306 @item E [ 1 J
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307 Erase from home position to point.
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308 @item E [ 2 J
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309 Erase whole sub-buffer.
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310 @item E [ K
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311 Erase from point to end of screen line.
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312 @item E [ 0 K
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313 Same as E [ K.
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314 @item E [ 1 K
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315 Erase from beginning of screen line to point.
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316 @item E [ 2 K
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317 Erase whole screen line.
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318 @end table
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319
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320 @node Inserting and deleting
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321 @subsection Escape sequences to insert and delete text
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322
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323 @table @kbd
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324 @item Esc [ N L
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325 Insert N (default 1) blank lines.
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326 @item Esc [ N M
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327 Delete N (default 1) lines.
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328 @item Esc [ N P
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329 Delete N (default 1) characters.
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330 @item Esc [ N @@
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331 Insert N (default 1) spaces.
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332 @end table
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333
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334 @node Scrolling
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335 @subsection Escape sequences to scroll part of the visible window
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336
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337 @table @kbd
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338 @item Esc D
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339 Scroll forward one screen line.
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340
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341 @item Esc M
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342 Scroll backwards one screen line.
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343
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344 @item Esc [ T ; B r
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345 Set the scrolling region to be from lines T down to line B inclusive,
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346 where line 1 is the topmost line.
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347 @end table
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348
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349 @node Command hook
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350 @subsection Command hook
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351
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352 If @kbd{C-z} is seen, any text up to a following @key{LF} is scanned.
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353 The text in between (not counting the initial C-z or the final LF)
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354 is passed to the function that is the value of @code{term-command-hook}.
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355
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356 The default value of the @code{term-command-hook} variable
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357 is the function @code{term-command-hook}, which handles the following:
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358
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359 @table @kbd
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360 @item C-z C-z FILENAME:LINENUMBER:IGNORED LF
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361 Set term-pending-frame to @code{(cons "FILENAME" LINENUMBER)}.
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362 When the buffer is displayed in the current window, show
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363 the FILENAME in the other window, and show an arrow at LINENUMBER.
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364 Gdb emits these strings when invoked with the flag --fullname.
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365 This is used by gdb mode; you can also invoke gdb with this flag
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366 from shell mode.
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367
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368 @item C-z / DIRNAME LF
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369 Set the directory of the term buffer to DIRNAME
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370
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371 @item C-z ! LEXPR LF
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372 Read and evaluate LEXPR as a Lisp expression.
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373 The result is ignored.
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374 @end table
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375
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376 @node Miscellaneous escapes
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377 @subsection Miscellaneous escapes
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378
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379 @table @kbd
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380 @item C-g (Bell)
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381 Calls @code{(beep t)}.
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382
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383 @item Esc 7
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384 Save cursor.
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385
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386 @item Esc 8
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387 Restore cursor.
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388
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389 @item Esc [ 47 h
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390 Switch to the alternate sub-buffer,
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391 @item Esc [ 47 l
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392 Switch back to the regular sub-buffer,
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393 @end table
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394
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395 @bye
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