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1 @comment node-name, next, previous, up
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2 @node Files, Other Customizations, Modes, Top
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3 @chapter Files
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4 @cindex files
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5
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6 The basic unit of stored data in Unix is the @dfn{file}. To edit a file,
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7 you must tell Emacs to read the file into a buffer. This is called
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8 @dfn{visiting} the file. You can now edit the buffer and to save the
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9 changes you must write the buffer back to the file.
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10
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11 In addition to visiting and saving files, Emacs can delete, copy, rename,
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12 and append to files, and operate on file directories.
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13
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14 @comment node-name, next, previous, up
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15 @menu
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16 * File Names:: How to type and edit file name arguments.
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17 * Visiting:: Visiting a file prepares Emacs to edit the file.
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18 * Saving Files:: How to save Emacs files.
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19 @end menu
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20
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21 @node File Names, Visiting, Files, Files
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22 @section File Names
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23 @cindex file names
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24
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25 Most of the Emacs commands that operate on a file require you to
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26 specify a file name. For example, you might specify the file name
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27 initially when you enter Emacs :
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28
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29 @example
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30 xemacs myfile RET
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31 @end example
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32
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33 @noindent
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34 After you hit @key{RET}, you will enter XEmacs with "myfile" read into
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35 the current buffer. If you do not specify the filename when entering
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36 Emacs, you can use the @b{Open...} option from the @b{File} menu. You
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37 will be prompted for a filename in the echo area:
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38
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39 @example
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40 Find file: /usr/workspace/
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41 @end example
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42
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43 @vindex default-directory
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44 @noindent
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45 Type in a file name which you want to open after the "/" and hit
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46 @key{RET}. The specified file will be read into the current buffer. The
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47 "/usr/workspace" might be the @dfn{default directory}. When Emacs
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48 prompts you for a file, it uses the default-directory unless you specify
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49 a directory. You can see what the default directory of the current
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50 buffer is by using the @b{Describe Variable} option from the @b{Help}
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51 menu. When Emacs prompts you for the variable name to describe, type
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52 @var{default-directory}. If you wish to open a file in some other
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53 directory, use @key{DEL} or the @key{BackSpace} key to go back and type
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54 the path name of the new directory.
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55
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56 You can create a new directory by typing @kbd{M-x
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57 make-directory}. This command will prompt you for a directory name:
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58
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59 @example
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60 Create directory: /usr/workspace/
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61 @end example
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62
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63 @findex make-directory
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64 @findex remove-directory
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65 @cindex creating-directories
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66 @cindex removing-directories
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67 @noindent
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68 After you type a directory name and press @key{RET}, a new directory
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69 with the specified name will be created. If you do not wish to create a
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70 new directory, then simply press @kbd{C-g} to quit the
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71 command. Similarly, you can also remove a directory by using the command
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72 @kbd{remove-directory}. The command @kbd{M-x pwd} will print the current
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73 buffer's default directory. For more information on file names,
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74 @xref{File Names,,,,XEmacs User's Manual}.
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75
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76
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77 @node Visiting, Saving Files, File Names, Files
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78 @section Visiting Files
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79 @cindex visiting files
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80
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81 To edit a file in Emacs you need to @dfn{visit} it. @dfn{Visiting} a
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82 file means copying its contents (or reading them) into the current
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83 buffer. Emacs will create a new buffer for each file that you visit. The
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84 buffer will be named after the file that you open. If you open a file
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85 @file{/usr/workspace/myfile.texinfo}, the buffer will be called
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86 "myfile.texinfo". If a buffer with this name already exists, a unique
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87 name will be constructed by appending @samp{<2>}, @samp{<3>}, etc. If
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88 this is the second buffer with the same name, a "<2>" will be appended,
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89 "<3>" for a third buffer and so on. The name of the buffer which is
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90 being displayed in the window will be shown both at the top and bottom
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91 of the frame. Once you are in XEmacs, you can use the following
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92 commands:
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93
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94 @table @kbd
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95 @item C-x C-f
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96 @findex find-file
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97 @kindex C-x C-f
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98 This command will visit a file (@code{find-file}). It will prompt you
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99 for a file name to visit. The @b{Open...} option from the @b{File} menu
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100 does the same thing:
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101
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102 @example
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103 Find file: /usr/workspace/
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104 @end example
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105
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106 @noindent
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107 Type in a filename and press @key{RET}. You will see a new buffer on the
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108 screen with its name in the mode-line. If the filename you specify
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109 already exists in Emacs, the buffer containing that file will be
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110 selected. You will get an error message if the filename does not
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111 exist. If you still press @key{RET}, a new buffer with the given
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112 filename will be displayed on the screen.
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113
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114 @item C-x C-v
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115 @kindex C-x C-v
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116 @findex find-alternate-file
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117 This command (@code{find-alternate-file}), will visit a different file
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118 instead of the one visited last. It is similar to @kbd{C-c C-f} except
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119 that it kills the current buffer (after offering to save it).
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120
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121 @item C-x 5 C-f
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122 @kindex C-x 5 C-f
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123 @findex find-file-other-frame
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124 This command will visit a file in another frame
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125 (@code{find-file-other-frame}) without changing the current window or
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126 frame. The @b{Open in New Frame...} from the @b{File} menu will do the
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127 same thing. It will prompt you for a file name in the echo area. After
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128 you type the file name and press @key{RET}, the specified file will be
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129 read into a new buffer and displayed on a new frame.
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130 @end table
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131
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132 @node Saving Files, , Visiting, Files
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133 @section Saving Files
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134 @cindex saving files
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135
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136 The changes that you make after visiting a file will not be saved
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137 unless you save the buffer. When you save the buffer, Emacs writes the
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138 current contents of the buffer into the visited file. Some commands to
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139 save buffers are:
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140
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141 @table @kbd
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142 @item C-x C-s
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143 @findex save-buffer
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144 @kindex C-x C-s
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145 This command will permanently save the current buffer in its visited
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146 file (@code{save-buffer}). You will see the following message in the
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147 echo area if you save a file called "myfile.texinfo" :
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148
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149 @example
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150 Wrote /usr/workspace/myfile.texinfo
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151 @end example
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152
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153 @noindent
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154 Try using this command twice. You will get the above message the first
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155 time you use this command, the second time you will get the following
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156 message:
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157
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158 @example
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159 (No changes need to be saved)
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160 @end example
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161
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162 @noindent
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163 This message indicates that you haven't made any changes since the last
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164 time you saved the file.
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165
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166 @item C-x s
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167 @kindex C-x s
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168 @findex save-some-buffers
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169 This command will save all the buffers in their visited files
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170 (@code{save-some-buffers}). It will prompt you for typing yes or no:
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171
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172 @example
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173 Save file /usr/workspace/myfile.texinfo? (y or n)
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174 @end example
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175
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176 @noindent
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177 You will get the above message for all the buffers. Type "y" if you want
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178 to save the buffer.
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179
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180 @item C-x C-w
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181 @findex write file
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182 @kindex C-x C-w
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183 This command will prompt you for a file name and save the current buffer
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184 in that file. (@code{write-file}). You will see the following message in
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185 the echo area:
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186
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187 @example
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188 Write file: /usr/workspace/
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189 @end example
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190
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191 @noindent
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192 After you type in a file name, press @key{RET}. The buffer will be saved
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193 in a new file. You can make copies of a particular file using this
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194 command.
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195 @end table
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196
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197 You can also undo all the changes made since the file was visited or
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198 saved by reading the text from the file again (called
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199 @dfn{reverting}). For more information on this option,
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200 @xref{Reverting,,,,XEmacs User's Manual}.
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201
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202 @vindex make-backup-files
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203 When you save a file in Emacs, it destroys its old contents. However,
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204 if you set the variable @var{make-backup-files} to non-@var{nil}
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205 i.e. @samp{t}, Emacs will create a @dfn{backup} file. Select the
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206 @b{Describe variable} option from the @b{Help} menu and look at the
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207 documentation for this variable. Its default value should be
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208 @samp{t}. However, if its not then use @kbd{M-x set-variable} to set it
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209 to @samp{t} (@pxref{Setting Variables}). The backup file will contain
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210 the contents from the last time you visited the file. Emacs also
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211 provides options for creating numbered backups. For more information on
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212 backups, @xref{Backup,,,,XEmacs User's Manual}.
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213
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214 @cindex auto saving
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215 Emacs also saves all the files from time to time so that in case of a
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216 system crash you don't lose lot of your work. You will see the message
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217 @samp{Auto-saving...} displayed in the echo area when the buffer is
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218 being saved automatically. The auto saved files are named by putting the
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219 character @samp{#} in front and back. For example a file called
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220 "myfile.texinfo" would be named as @file{#myfile.texinfo#}. For
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221 information on controlling auto-saving and recovering data from
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222 auto-saving, @xref{Auto Save Files,,,,XEmacs User's Manual}.
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223
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224 @cindex simultaneous editing
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225 Emacs provides protection from simultaneous editing which occurs if
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226 two users are visiting the same file and trying to save their
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227 changes. It will put a lock on a file which is being visited and
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228 modified. If any other user tries to modify that file, it will inform
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229 the user about the lock and provide some
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230 options. For more information on protection against simultaneous
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231 editing, @xref{Interlocking,,,,XEmacs User's Manual}.
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232
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