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1
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2 @node Help, Mark, M-x, Top
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3 @chapter Help
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4 @cindex help
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5 @cindex self-documentation
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6
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7 Emacs provides extensive help features which revolve around a single
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8 character, @kbd{C-h}. @kbd{C-h} is a prefix key that is used only for
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9 documentation-printing commands. The characters you can type after
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10 @kbd{C-h} are called @dfn{help options}. One help option is @kbd{C-h};
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11 you use it to ask for help about using @kbd{C-h}.
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12
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13 @kbd{C-h C-h} prints a list of the possible help options, and then asks
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14 you to type the desired option. It prompts with the string:
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15
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16 @smallexample
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17 A, B, C, F, I, K, L, M, N, S, T, V, W, C-c, C-d, C-n, C-w or C-h for more help:
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18 @end smallexample
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19
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20 @noindent
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21 You should type one of those characters.
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22
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23 Typing a third @kbd{C-h} displays a description of what the options mean;
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24 Emacs still waits for you to type an option. To cancel, type @kbd{C-g}.
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25
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26 Here is a summary of the defined help commands.
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27
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28 @table @kbd
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29 @item C-h a @var{string} @key{RET}
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30 Display a list of commands whose names contain @var{string}
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31 (@code{command-@*apropos}).@refill
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32 @item C-h b
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33 Display a table of all key bindings currently in effect, with local bindings of
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34 the current major mode first, followed by all global bindings
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35 (@code{describe-bindings}).
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36 @item C-h c @var{key}
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37 Print the name of the command that @var{key} runs (@code{describe-key-@*briefly}).
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38 @kbd{c} is for `character'. For more extensive information on @var{key},
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39 use @kbd{C-h k}.
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40 @item C-h f @var{function} @key{RET}
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41 Display documentation on the Lisp function named @var{function}
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42 (@code{describe-function}). Note that commands are Lisp functions, so
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43 a command name may be used.
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44 @item C-h i
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45 Run Info, the program for browsing documentation files (@code{info}).
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46 The complete Emacs manual is available online in Info.
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47 @item C-h k @var{key}
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48 Display name and documentation of the command @var{key} runs (@code{describe-key}).
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49 @item C-h l
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50 Display a description of the last 100 characters you typed
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51 (@code{view-lossage}).
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52 @item C-h m
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53 Display documentation of the current major mode (@code{describe-mode}).
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54 @item C-h n
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55 Display documentation of Emacs changes, most recent first
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56 (@code{view-emacs-news}).
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57 @item C-h p
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58 Display a table of all mouse bindings currently in effect now, with
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59 local bindings of the current major mode first, followed by all global bindings
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60 (@code{describe-pointer}).
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61 @item C-h s
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62 Display current contents of the syntax table, plus an explanation of
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63 what they mean (@code{describe-syntax}).
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64 @item C-h t
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65 Display the Emacs tutorial (@code{help-with-tutorial}).
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66 @item C-h v @var{var} @key{RET}
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67 Display the documentation of the Lisp variable @var{var}
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68 (@code{describe-@*variable}).
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69 @item C-h w @var{command} @key{RET}
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70 Print which keys run the command named @var{command} (@code{where-is}).
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71 @item M-x apropos @var{regexp}
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72 Show all symbols whose names contain matches for @var{regexp}.
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73 @end table
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74
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75 @section Documentation for a Key
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76
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77 @kindex C-h c
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78 @findex describe-key-briefly
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79 The most basic @kbd{C-h} options are @kbd{C-h c}
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80 (@code{describe-key-briefly}) and @kbd{C-h k}@*(@code{describe-key}).
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81 @kbd{C-h c @var{key}} prints the name of the command that @var{key} is
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82 bound to in the echo area. For example, @kbd{C-h c C-f} prints
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83 @samp{forward-char}. Since command names are chosen to describe what
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84 the command does, using this option is a good way to get a somewhat cryptic
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85 description of what @var{key} does.@refill
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86
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87 @kindex C-h k
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88 @findex describe-key
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89 @kbd{C-h k @var{key}} is similar to @kbd{C-h c} but gives more
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90 information. It displays the documentation string of the function
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91 @var{key} is bound to as well as its name. @var{key} is a string or
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92 vector of events. When called interactively, @var{key} may also be a menu
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93 selection. This information does not usually fit into the echo area, so a
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94 window is used for the display.
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95
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96 @section Help by Command or Variable Name
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97
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98 @kindex C-h f
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99 @findex describe-function
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100 @vindex describe-function-show-arglist
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101 @kbd{C-h f} (@code{describe-function}) reads the name of a Lisp
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102 function using the minibuffer, then displays that function's
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103 documentation string in a window. Since commands are Lisp functions,
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104 you can use the argument @var{function} to get the documentation of a
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105 command that you know by name. For example,
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106
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107 @example
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108 C-h f auto-fill-mode @key{RET}
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109 @end example
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110
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111 @noindent
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112 displays the documentation for @code{auto-fill-mode}. Using @kbd{C-h f}
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113 is the only way to see the documentation of a command that is not bound
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114 to any key, that is, a command you would normally call using @kbd{M-x}.
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115 If the variable @code{describe-function-show-arglist} is @code{t},
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116 @code{describe-function} shows its arglist if the @var{function} is not
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117 an autoload function.
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118
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119 @kbd{C-h f} is also useful for Lisp functions you are planning to
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120 use in a Lisp program. For example, if you have just written the code
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121 @code{(make-vector len)} and want to make sure you are using
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122 @code{make-vector} properly, type @kbd{C-h f make-vector @key{RET}}. Because
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123 @kbd{C-h f} allows all function names, not just command names, you may find
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124 that some of your favorite abbreviations that work in @kbd{M-x} don't work
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125 in @kbd{C-h f}. An abbreviation may be unique among command names, yet fail
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126 to be unique when other function names are allowed.
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127
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128
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129 If you type @key{RET}, leaving the minibuffer empty, @kbd{C-h f} by
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130 default describes the function called by the innermost Lisp expression
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131 in the buffer around point, @i{provided} that that is a valid, defined Lisp
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132 function name. For example, if point is located following the text
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133 @samp{(make-vector (car x)}, the innermost list containing point is the
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134 one starting with @samp{(make-vector}, so the default is to describe
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135 the function @code{make-vector}.
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136
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137 @kbd{C-h f} is often useful just to verify that you have the right
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138 spelling for the function name. If @kbd{C-h f} mentions a default in the
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139 prompt, you have typed the name of a defined Lisp function. If that is
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140 what you wanted to know, just type @kbd{C-g} to cancel the @kbd{C-h f}
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141 command and continue editing.
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142
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143 @kindex C-h w
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144 @findex where-is
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145 @kbd{C-h w @var{command} @key{RET}} (@code{where-s}) tells you what
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146 keys are bound to @var{command}. It prints a list of the keys in the
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147 echo area. Alternatively, it informs you that a command is not bound to
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148 any keys, which implies that you must use @kbd{M-x} to call the
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149 command.@refill
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150
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151 @kindex C-h v
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152 @findex describe-variable
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153 @kbd{C-h v} (@code{describe-variable}) is like @kbd{C-h f} but
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154 describes Lisp variables instead of Lisp functions. Its default is the
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155 Lisp symbol around or before point, if that is the name of a known Lisp
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156 variable. @xref{Variables}.@refill
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157
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158 @section Apropos
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159
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160 @kindex C-h a
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161 @findex command-apropos
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162 @cindex apropos
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163
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164 @table @kbd
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165 @item C-h a
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166 Show only symbols that are names of commands
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167 (@code{command-apropos}).@refill
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168
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169 @item M-x apropos @var{regexp}
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170 Show all symbols whose names comtain matches for @var{regexp}.
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171 @end table
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172
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173 It is possible to ask a question like, ``What are the commands for
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174 working with files?'' To do this, type @kbd{C-h a file @key{RET}},
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175 which displays a list of all command names that contain @samp{file},
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176 such as @code{copy-file}, @code{find-file}, and so on. With each
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177 command name a brief description of its use and information on the keys
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178 you can use to invoke it is displayed. For example, you would be
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179 informed that you can invoke @code{find-file} by typing @kbd{C-x C-f}.
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180 The @kbd{a} in @kbd{C-h a} stands for `Apropos'; @kbd{C-h a} runs the
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181 Lisp function @code{command-apropos}.@refill
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182
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183 Because @kbd{C-h a} looks only for functions whose names contain the
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184 string you specify, you must use ingenuity in choosing the string. If
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185 you are looking for commands for killing backwards and @kbd{C-h a
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186 kill-backwards @key{RET}} doesn't reveal any commands, don't give up.
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187 Try just @kbd{kill}, or just @kbd{backwards}, or just @kbd{back}. Be
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188 persistent. Pretend you are playing Adventure. Also note that you can
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189 use a regular expression as the argument (@pxref{Regexps}).
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190
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191 Here is a set of arguments to give to @kbd{C-h a} that covers many
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192 classes of Emacs commands, since there are strong conventions for naming
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193 standard Emacs commands. By giving you a feeling for the naming
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194 conventions, this set of arguments can also help you develop a
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195 technique for picking @code{apropos} strings.
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196
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197 @quotation
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198 char, line, word, sentence, paragraph, region, page, sexp, list, defun,
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199 buffer, frame, window, file, dir, register, mode,
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200 beginning, end, forward, backward, next, previous, up, down, search, goto,
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201 kill, delete, mark, insert, yank, fill, indent, case,
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202 change, set, what, list, find, view, describe.
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203 @end quotation
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204
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205 @findex apropos
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206 To list all Lisp symbols that contain a match for a regexp, not just
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207 the ones that are defined as commands, use the command @kbd{M-x apropos}
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208 instead of @kbd{C-h a}.
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209
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210 @section Other Help Commands
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211
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212 @kindex C-h i
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213 @findex info
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214 @kbd{C-h i} (@code{info}) runs the Info program, which is used for
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215 browsing through structured documentation files. The entire Emacs manual
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216 is available within Info. Eventually all the documentation of the GNU
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217 system will be available. Type @kbd{h} after entering Info to run
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218 a tutorial on using Info.
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219
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220 @kindex C-h l
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221 @findex view-lossage
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222 If something surprising happens, and you are not sure what commands you
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223 typed, use @kbd{C-h l} (@code{view-lossage}). @kbd{C-h l} prints the last
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224 100 command characters you typed. If you see commands you don't
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225 know, use @kbd{C-h c} to find out what they do.
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226
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227 @kindex C-h m
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228 @findex describe-mode
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229 Emacs has several major modes. Each mode redefines a few keys and
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230 makes a few other changes in how editing works. @kbd{C-h m}
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231 (@code{describe-mode}) prints documentation on the current major mode,
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232 which normally describes all the commands that are changed in this mode.
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233
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234 @kindex C-h b
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235 @findex describe-bindings
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236 @kbd{C-h b} (@code{describe-bindings}) and @kbd{C-h s}
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237 (@code{describe-syntax}) present information about the current Emacs
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238 mode that is not covered by @kbd{C-h m}. @kbd{C-h b} displays a list of
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239 all key bindings currently in effect, with the local bindings of the current
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240 major mode first, followed by the global bindings (@pxref{Key
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241 Bindings}). @kbd{C-h s} displays the contents of the syntax table with
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242 explanations of each character's syntax (@pxref{Syntax}).@refill
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243
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244 @kindex C-h n
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245 @findex view-emacs-news
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246 @kindex C-h t
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247 @findex help-with-tutorial
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248 @kindex C-h C-c
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249 @findex describe-copying
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250 @kindex C-h C-d
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251 @findex describe-distribution
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252 @kindex C-h C-w
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253 @findex describe-no-warranty
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254 The other @kbd{C-h} options display various files of useful
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255 information. @kbd{C-h C-w} (@code{describe-no-warranty}) displays
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256 details on the complete absence of warranty for XEmacs. @kbd{C-h n}
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257 (@code{view-emacs-news}) displays the file @file{emacs/etc/NEWS}, which
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258 contains documentation on Emacs changes arranged chronologically.
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259 @kbd{C-h t} (@code{help-with-tutorial}) displays the learn-by-doing
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260 Emacs tutorial. @kbd{C-h C-c} (@code{describe-copying}) displays the file
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261 @file{emacs/etc/COPYING}, which tells you the conditions you must obey
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262 in distributing copies of Emacs. @kbd{C-h C-d}
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263 (@code{describe-distribution}) displays another file named
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264 @file{emacs/etc/DISTRIB}, which tells you how you can order a copy of
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265 the latest version of Emacs.@refill
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