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1 *usr_23.txt* For Vim version 8.2. Last change: 2020 Dec 19
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3 VIM USER MANUAL - by Bram Moolenaar
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4
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5 Editing other files
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6
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7
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8 This chapter is about editing files that are not ordinary files. With Vim you
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9 can edit files that are compressed or encrypted. Some files need to be
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10 accessed over the internet. With some restrictions, binary files can be
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11 edited as well.
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12
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13 |23.1| DOS, Mac and Unix files
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14 |23.2| Files on the internet
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15 |23.3| Encryption
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16 |23.4| Binary files
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17 |23.5| Compressed files
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18
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19 Next chapter: |usr_24.txt| Inserting quickly
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20 Previous chapter: |usr_22.txt| Finding the file to edit
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21 Table of contents: |usr_toc.txt|
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22
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23 ==============================================================================
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24 *23.1* DOS, Mac and Unix files
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25
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26 Back in the early days, the old Teletype machines used two characters to
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27 start a new line. One to move the carriage back to the first position
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28 (carriage return, <CR>), another to move the paper up (line feed, <LF>).
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29 When computers came out, storage was expensive. Some people decided that
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30 they did not need two characters for end-of-line. The UNIX people decided
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31 they could use <New Line> or <NL> only for end-of-line. The Apple people
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32 standardized on <CR>. The Microsoft Windows folks decided to keep the old
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33 <CR><NL> (we use <NL> for line feed in the help text).
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34 This means that if you try to move a file from one system to another, you
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35 have line-break problems. The Vim editor automatically recognizes the
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36 different file formats and handles things properly behind your back.
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37 The option 'fileformats' contains the various formats that will be tried
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38 when a new file is edited. The following command, for example, tells Vim to
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39 try UNIX format first and MS-DOS format second: >
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40
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41 :set fileformats=unix,dos
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42
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43 You will notice the format in the message you get when editing a file. You
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44 don't see anything if you edit a native file format. Thus editing a Unix file
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45 on Unix won't result in a remark. But when you edit a dos file, Vim will
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46 notify you of this:
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47
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48 "/tmp/test" [dos] 3L, 71C ~
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49
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50 For a Mac file you would see "[mac]".
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51 The detected file format is stored in the 'fileformat' option. To see
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52 which format you have, execute the following command: >
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53
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54 :set fileformat?
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55
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56 The three names that Vim uses are:
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57
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58 unix <NL>
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59 dos <CR><NL>
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60 mac <CR>
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61
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62
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63 USING THE MAC FORMAT
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64
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65 On Unix, <NL> is used to break a line. It's not unusual to have a <CR>
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66 character halfway a line. Incidentally, this happens quite often in Vi (and
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67 Vim) scripts.
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68 On the Macintosh, where <CR> is the line break character, it's possible to
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69 have a <NL> character halfway a line.
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70 The result is that it's not possible to be 100% sure whether a file
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71 containing both <CR> and <NL> characters is a Mac or a Unix file. Therefore,
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72 Vim assumes that on Unix you probably won't edit a Mac file, and doesn't check
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73 for this type of file. To check for this format anyway, add "mac" to
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74 'fileformats': >
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75
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76 :set fileformats+=mac
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77
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78 Then Vim will take a guess at the file format. Watch out for situations where
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79 Vim guesses wrong.
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80
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81
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82 OVERRULING THE FORMAT
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83
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84 If you use the good old Vi and try to edit an MS-DOS format file, you will
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85 find that each line ends with a ^M character. (^M is <CR>). The automatic
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86 detection avoids this. Suppose you do want to edit the file that way? Then
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87 you need to overrule the format: >
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88
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89 :edit ++ff=unix file.txt
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90
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91 The "++" string is an item that tells Vim that an option name follows, which
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92 overrules the default for this single command. "++ff" is used for
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93 'fileformat'. You could also use "++ff=mac" or "++ff=dos".
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94 This doesn't work for any option, only "++ff" and "++enc" are currently
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95 implemented. The full names "++fileformat" and "++encoding" also work.
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96
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97
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98 CONVERSION
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99
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100 You can use the 'fileformat' option to convert from one file format to
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101 another. Suppose, for example, that you have an MS-DOS file named README.TXT
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102 that you want to convert to UNIX format. Start by editing the MS-DOS format
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103 file: >
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104 vim README.TXT
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105
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106 Vim will recognize this as a dos format file. Now change the file format to
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107 UNIX: >
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108
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109 :set fileformat=unix
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110 :write
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111
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112 The file is written in Unix format.
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113
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114 ==============================================================================
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115 *23.2* Files on the internet
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116
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117 Someone sends you an e-mail message, which refers to a file by its URL. For
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118 example:
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119
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120 You can find the information here: ~
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121 ftp://ftp.vim.org/pub/vim/README ~
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122
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123 You could start a program to download the file, save it on your local disk and
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124 then start Vim to edit it.
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125 There is a much simpler way. Move the cursor to any character of the URL.
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126 Then use this command: >
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127
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128 gf
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129
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130 With a bit of luck, Vim will figure out which program to use for downloading
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131 the file, download it and edit the copy. To open the file in a new window use
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132 CTRL-W f.
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133 If something goes wrong you will get an error message. It's possible that
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134 the URL is wrong, you don't have permission to read it, the network connection
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135 is down, etc. Unfortunately, it's hard to tell the cause of the error. You
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136 might want to try the manual way of downloading the file.
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137
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138 Accessing files over the internet works with the netrw plugin. Currently URLs
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139 with these formats are recognized:
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140
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141 ftp:// uses ftp
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142 rcp:// uses rcp
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143 scp:// uses scp
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144 http:// uses wget (reading only)
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145
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146 Vim doesn't do the communication itself, it relies on the mentioned programs
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147 to be available on your computer. On most Unix systems "ftp" and "rcp" will
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148 be present. "scp" and "wget" might need to be installed.
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149
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150 Vim detects these URLs for each command that starts editing a new file, also
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151 with ":edit" and ":split", for example. Write commands also work, except for
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152 http://.
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153
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154 For more information, also about passwords, see |netrw|.
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155
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156 ==============================================================================
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157 *23.3* Encryption
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158
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159 Some information you prefer to keep to yourself. For example, when writing
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160 a test on a computer that students also use. You don't want clever students
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161 to figure out a way to read the questions before the exam starts. Vim can
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162 encrypt the file for you, which gives you some protection.
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163 To start editing a new file with encryption, use the "-x" argument to start
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164 Vim. Example: >
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165
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166 vim -x exam.txt
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167
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168 Vim prompts you for a key used for encrypting and decrypting the file:
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169
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170 Enter encryption key: ~
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171
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172 Carefully type the secret key now. You cannot see the characters you type,
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173 they will be replaced by stars. To avoid the situation that a typing mistake
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174 will cause trouble, Vim asks you to enter the key again:
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175
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176 Enter same key again: ~
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177
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178 You can now edit this file normally and put in all your secrets. When you
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179 finish editing the file and tell Vim to exit, the file is encrypted and
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180 written.
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181 When you edit the file with Vim, it will ask you to enter the same key
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182 again. You don't need to use the "-x" argument. You can also use the normal
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183 ":edit" command. Vim adds a magic string to the file by which it recognizes
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184 that the file was encrypted.
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185 If you try to view this file using another program, all you get is garbage.
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186 Also, if you edit the file with Vim and enter the wrong key, you get garbage.
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187 Vim does not have a mechanism to check if the key is the right one (this makes
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188 it much harder to break the key).
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189
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190
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191 SWITCHING ENCRYPTION ON AND OFF
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192
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193 To disable the encryption of a file, set the 'key' option to an empty string:
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194 >
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195 :set key=
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196
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197 The next time you write the file this will be done without encryption.
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198 Setting the 'key' option to enable encryption is not a good idea, because
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199 the password appears in the clear. Anyone shoulder-surfing can read your
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200 password.
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201 To avoid this problem, the ":X" command was created. It asks you for an
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202 encryption key, just like the "-x" argument did: >
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203
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204 :X
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205 Enter encryption key: ******
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206 Enter same key again: ******
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207
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208
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209 LIMITS ON ENCRYPTION
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210
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211 The encryption algorithm used by Vim is not very strong. It is good enough to
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212 keep out the casual prowler, but not good enough to keep out a cryptology
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213 expert with lots of time on his hands. The text in the swap file and the undo
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214 file is also encrypted. However, this is done block-by-block and may reduce
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215 the time needed to crack a password. You can disable the swap file, but then
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216 a crash will cause you to lose your work, since Vim keeps all the text in
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217 memory only. The undo file can be disabled with the only disadvantage that
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218 you can't undo after unloading the buffer.
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219 To avoid using a swap file, supply the -n argument on the command line.
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220 For example, to edit the encrypted file "file.txt" without a swap file use the
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221 following command: >
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222
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223 vim -x -n file.txt
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224
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225 When already editing a file, the swapfile can be disabled with: >
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226
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227 :setlocal noswapfile
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228
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229 Since there is no swapfile, recovery will be impossible. Save the file a bit
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230 more often to avoid the risk of losing your changes.
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231
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232 While the file is in memory, it is in plain text. Anyone with privilege can
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233 look in the editor's memory and discover the contents of the file.
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234 If you use a viminfo file, be aware that the contents of text registers are
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235 written out in the clear as well.
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236 If you really want to secure the contents of a file, edit it only on a
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237 portable computer not connected to a network, use good encryption tools, and
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238 keep the computer locked up in a big safe when not in use.
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239
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240 ==============================================================================
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241 *23.4* Binary files
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242
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243 You can edit binary files with Vim. Vim wasn't really made for this, thus
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244 there are a few restrictions. But you can read a file, change a character and
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245 write it back, with the result that only that one character was changed and
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246 the file is identical otherwise.
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247 To make sure that Vim does not use its clever tricks in the wrong way, add
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248 the "-b" argument when starting Vim: >
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249
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250 vim -b datafile
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251
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252 This sets the 'binary' option. The effect of this is that unexpected side
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253 effects are turned off. For example, 'textwidth' is set to zero, to avoid
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254 automatic formatting of lines. And files are always read in Unix file format.
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255
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256 Binary mode can be used to change a message in a program. Be careful not to
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257 insert or delete any characters, it would stop the program from working. Use
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258 "R" to enter replace mode.
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259
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260 Many characters in the file will be unprintable. To see them in Hex format: >
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261
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262 :set display=uhex
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263
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264 Otherwise, the "ga" command can be used to see the value of the character
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265 under the cursor. The output, when the cursor is on an <Esc>, looks like
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266 this:
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267
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268 <^[> 27, Hex 1b, Octal 033 ~
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269
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270 There might not be many line breaks in the file. To get some overview switch
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271 the 'wrap' option off: >
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272
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273 :set nowrap
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274
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275
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276 BYTE POSITION
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277
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278 To see on which byte you are in the file use this command: >
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279
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280 g CTRL-G
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281
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282 The output is verbose:
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283
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284 Col 9-16 of 9-16; Line 277 of 330; Word 1806 of 2058; Byte 10580 of 12206 ~
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285
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286 The last two numbers are the byte position in the file and the total number of
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287 bytes. This takes into account how 'fileformat' changes the number of bytes
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288 that a line break uses.
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289 To move to a specific byte in the file, use the "go" command. For
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290 example, to move to byte 2345: >
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291
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292 2345go
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293
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294
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295 USING XXD
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296
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297 A real binary editor shows the text in two ways: as it is and in hex format.
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298 You can do this in Vim by first converting the file with the "xxd" program.
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299 This comes with Vim.
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300 First edit the file in binary mode: >
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301
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302 vim -b datafile
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303
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304 Now convert the file to a hex dump with xxd: >
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305
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306 :%!xxd
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307
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308 The text will look like this:
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309
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310 0000000: 1f8b 0808 39d7 173b 0203 7474 002b 4e49 ....9..;..tt.+NI ~
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311 0000010: 4b2c 8660 eb9c ecac c462 eb94 345e 2e30 K,.`.....b..4^.0 ~
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312 0000020: 373b 2731 0b22 0ca6 c1a2 d669 1035 39d9 7;'1.".....i.59. ~
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313
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314 You can now view and edit the text as you like. Vim treats the information as
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315 ordinary text. Changing the hex does not cause the printable character to be
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316 changed, or the other way around.
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317 Finally convert it back with:
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318 >
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319 :%!xxd -r
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320
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321 Only changes in the hex part are used. Changes in the printable text part on
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322 the right are ignored.
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323
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324 See the manual page of xxd for more information.
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325
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326 ==============================================================================
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327 *23.5* Compressed files
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328
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329 This is easy: You can edit a compressed file just like any other file. The
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330 "gzip" plugin takes care of decompressing the file when you edit it. And
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331 compressing it again when you write it.
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332 These compression methods are currently supported:
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333
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334 .Z compress
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335 .gz gzip
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336 .bz2 bzip2
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337
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338 Vim uses the mentioned programs to do the actual compression and
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339 decompression. You might need to install the programs first.
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340
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341 ==============================================================================
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342
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343 Next chapter: |usr_24.txt| Inserting quickly
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344
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345 Copyright: see |manual-copyright| vim:tw=78:ts=8:noet:ft=help:norl:
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