diff options
Diffstat (limited to 'runtime/doc/usr_23.txt')
| -rw-r--r-- | runtime/doc/usr_23.txt | 345 |
1 files changed, 345 insertions, 0 deletions
diff --git a/runtime/doc/usr_23.txt b/runtime/doc/usr_23.txt new file mode 100644 index 0000000..016f742 --- /dev/null +++ b/runtime/doc/usr_23.txt @@ -0,0 +1,345 @@ +*usr_23.txt* For Vim version 9.1. Last change: 2020 Dec 19 + + VIM USER MANUAL - by Bram Moolenaar + + Editing other files + + +This chapter is about editing files that are not ordinary files. With Vim you +can edit files that are compressed or encrypted. Some files need to be +accessed over the internet. With some restrictions, binary files can be +edited as well. + +|23.1| DOS, Mac and Unix files +|23.2| Files on the internet +|23.3| Encryption +|23.4| Binary files +|23.5| Compressed files + + Next chapter: |usr_24.txt| Inserting quickly + Previous chapter: |usr_22.txt| Finding the file to edit +Table of contents: |usr_toc.txt| + +============================================================================== +*23.1* DOS, Mac and Unix files + +Back in the early days, the old Teletype machines used two characters to +start a new line. One to move the carriage back to the first position +(carriage return, <CR>), another to move the paper up (line feed, <LF>). + When computers came out, storage was expensive. Some people decided that +they did not need two characters for end-of-line. The UNIX people decided +they could use <New Line> or <NL> only for end-of-line. The Apple people +standardized on <CR>. The Microsoft Windows folks decided to keep the old +<CR><NL> (we use <NL> for line feed in the help text). + This means that if you try to move a file from one system to another, you +have line-break problems. The Vim editor automatically recognizes the +different file formats and handles things properly behind your back. + The option 'fileformats' contains the various formats that will be tried +when a new file is edited. The following command, for example, tells Vim to +try UNIX format first and MS-DOS format second: > + + :set fileformats=unix,dos + +You will notice the format in the message you get when editing a file. You +don't see anything if you edit a native file format. Thus editing a Unix file +on Unix won't result in a remark. But when you edit a dos file, Vim will +notify you of this: + + "/tmp/test" [dos] 3L, 71C ~ + +For a Mac file you would see "[mac]". + The detected file format is stored in the 'fileformat' option. To see +which format you have, execute the following command: > + + :set fileformat? + +The three names that Vim uses are: + + unix <NL> + dos <CR><NL> + mac <CR> + + +USING THE MAC FORMAT + +On Unix, <NL> is used to break a line. It's not unusual to have a <CR> +character halfway a line. Incidentally, this happens quite often in Vi (and +Vim) scripts. + On the Macintosh, where <CR> is the line break character, it's possible to +have a <NL> character halfway a line. + The result is that it's not possible to be 100% sure whether a file +containing both <CR> and <NL> characters is a Mac or a Unix file. Therefore, +Vim assumes that on Unix you probably won't edit a Mac file, and doesn't check +for this type of file. To check for this format anyway, add "mac" to +'fileformats': > + + :set fileformats+=mac + +Then Vim will take a guess at the file format. Watch out for situations where +Vim guesses wrong. + + +OVERRULING THE FORMAT + +If you use the good old Vi and try to edit an MS-DOS format file, you will +find that each line ends with a ^M character. (^M is <CR>). The automatic +detection avoids this. Suppose you do want to edit the file that way? Then +you need to overrule the format: > + + :edit ++ff=unix file.txt + +The "++" string is an item that tells Vim that an option name follows, which +overrules the default for this single command. "++ff" is used for +'fileformat'. You could also use "++ff=mac" or "++ff=dos". + This doesn't work for any option, only "++ff" and "++enc" are currently +implemented. The full names "++fileformat" and "++encoding" also work. + + +CONVERSION + +You can use the 'fileformat' option to convert from one file format to +another. Suppose, for example, that you have an MS-DOS file named README.TXT +that you want to convert to UNIX format. Start by editing the MS-DOS format +file: > + vim README.TXT + +Vim will recognize this as a dos format file. Now change the file format to +UNIX: > + + :set fileformat=unix + :write + +The file is written in Unix format. + +============================================================================== +*23.2* Files on the internet + +Someone sends you an e-mail message, which refers to a file by its URL. For +example: + + You can find the information here: ~ + ftp://ftp.vim.org/pub/vim/README ~ + +You could start a program to download the file, save it on your local disk and +then start Vim to edit it. + There is a much simpler way. Move the cursor to any character of the URL. +Then use this command: > + + gf + +With a bit of luck, Vim will figure out which program to use for downloading +the file, download it and edit the copy. To open the file in a new window use +CTRL-W f. + If something goes wrong you will get an error message. It's possible that +the URL is wrong, you don't have permission to read it, the network connection +is down, etc. Unfortunately, it's hard to tell the cause of the error. You +might want to try the manual way of downloading the file. + +Accessing files over the internet works with the netrw plugin. Currently URLs +with these formats are recognized: + + ftp:// uses ftp + rcp:// uses rcp + scp:// uses scp + http:// uses wget (reading only) + +Vim doesn't do the communication itself, it relies on the mentioned programs +to be available on your computer. On most Unix systems "ftp" and "rcp" will +be present. "scp" and "wget" might need to be installed. + +Vim detects these URLs for each command that starts editing a new file, also +with ":edit" and ":split", for example. Write commands also work, except for +http://. + +For more information, also about passwords, see |netrw|. + +============================================================================== +*23.3* Encryption + +Some information you prefer to keep to yourself. For example, when writing +a test on a computer that students also use. You don't want clever students +to figure out a way to read the questions before the exam starts. Vim can +encrypt the file for you, which gives you some protection. + To start editing a new file with encryption, use the "-x" argument to start +Vim. Example: > + + vim -x exam.txt + +Vim prompts you for a key used for encrypting and decrypting the file: + + Enter encryption key: ~ + +Carefully type the secret key now. You cannot see the characters you type, +they will be replaced by stars. To avoid the situation that a typing mistake +will cause trouble, Vim asks you to enter the key again: + + Enter same key again: ~ + +You can now edit this file normally and put in all your secrets. When you +finish editing the file and tell Vim to exit, the file is encrypted and +written. + When you edit the file with Vim, it will ask you to enter the same key +again. You don't need to use the "-x" argument. You can also use the normal +":edit" command. Vim adds a magic string to the file by which it recognizes +that the file was encrypted. + If you try to view this file using another program, all you get is garbage. +Also, if you edit the file with Vim and enter the wrong key, you get garbage. +Vim does not have a mechanism to check if the key is the right one (this makes +it much harder to break the key). + + +SWITCHING ENCRYPTION ON AND OFF + +To disable the encryption of a file, set the 'key' option to an empty string: +> + :set key= + +The next time you write the file this will be done without encryption. + Setting the 'key' option to enable encryption is not a good idea, because +the password appears in the clear. Anyone shoulder-surfing can read your +password. + To avoid this problem, the ":X" command was created. It asks you for an +encryption key, just like the "-x" argument did: > + + :X + Enter encryption key: ****** + Enter same key again: ****** + + +LIMITS ON ENCRYPTION + +The encryption algorithm used by Vim is not very strong. It is good enough to +keep out the casual prowler, but not good enough to keep out a cryptology +expert with lots of time on his hands. The text in the swap file and the undo +file is also encrypted. However, this is done block-by-block and may reduce +the time needed to crack a password. You can disable the swap file, but then +a crash will cause you to lose your work, since Vim keeps all the text in +memory only. The undo file can be disabled with the only disadvantage that +you can't undo after unloading the buffer. + To avoid using a swap file, supply the -n argument on the command line. +For example, to edit the encrypted file "file.txt" without a swap file use the +following command: > + + vim -x -n file.txt + +When already editing a file, the swapfile can be disabled with: > + + :setlocal noswapfile + +Since there is no swapfile, recovery will be impossible. Save the file a bit +more often to avoid the risk of losing your changes. + +While the file is in memory, it is in plain text. Anyone with privilege can +look in the editor's memory and discover the contents of the file. + If you use a viminfo file, be aware that the contents of text registers are +written out in the clear as well. + If you really want to secure the contents of a file, edit it only on a +portable computer not connected to a network, use good encryption tools, and +keep the computer locked up in a big safe when not in use. + +============================================================================== +*23.4* Binary files + +You can edit binary files with Vim. Vim wasn't really made for this, thus +there are a few restrictions. But you can read a file, change a character and +write it back, with the result that only that one character was changed and +the file is identical otherwise. + To make sure that Vim does not use its clever tricks in the wrong way, add +the "-b" argument when starting Vim: > + + vim -b datafile + +This sets the 'binary' option. The effect of this is that unexpected side +effects are turned off. For example, 'textwidth' is set to zero, to avoid +automatic formatting of lines. And files are always read in Unix file format. + +Binary mode can be used to change a message in a program. Be careful not to +insert or delete any characters, it would stop the program from working. Use +"R" to enter replace mode. + +Many characters in the file will be unprintable. To see them in Hex format: > + + :set display=uhex + +Otherwise, the "ga" command can be used to see the value of the character +under the cursor. The output, when the cursor is on an <Esc>, looks like +this: + + <^[> 27, Hex 1b, Octal 033 ~ + +There might not be many line breaks in the file. To get some overview switch +the 'wrap' option off: > + + :set nowrap + + +BYTE POSITION + +To see on which byte you are in the file use this command: > + + g CTRL-G + +The output is verbose: + + Col 9-16 of 9-16; Line 277 of 330; Word 1806 of 2058; Byte 10580 of 12206 ~ + +The last two numbers are the byte position in the file and the total number of +bytes. This takes into account how 'fileformat' changes the number of bytes +that a line break uses. + To move to a specific byte in the file, use the "go" command. For +example, to move to byte 2345: > + + 2345go + + +USING XXD + +A real binary editor shows the text in two ways: as it is and in hex format. +You can do this in Vim by first converting the file with the "xxd" program. +This comes with Vim. + First edit the file in binary mode: > + + vim -b datafile + +Now convert the file to a hex dump with xxd: > + + :%!xxd + +The text will look like this: + + 0000000: 1f8b 0808 39d7 173b 0203 7474 002b 4e49 ....9..;..tt.+NI ~ + 0000010: 4b2c 8660 eb9c ecac c462 eb94 345e 2e30 K,.`.....b..4^.0 ~ + 0000020: 373b 2731 0b22 0ca6 c1a2 d669 1035 39d9 7;'1.".....i.59. ~ + +You can now view and edit the text as you like. Vim treats the information as +ordinary text. Changing the hex does not cause the printable character to be +changed, or the other way around. + Finally convert it back with: +> + :%!xxd -r + +Only changes in the hex part are used. Changes in the printable text part on +the right are ignored. + +See the manual page of xxd for more information. + +============================================================================== +*23.5* Compressed files + +This is easy: You can edit a compressed file just like any other file. The +"gzip" plugin takes care of decompressing the file when you edit it. And +compressing it again when you write it. + These compression methods are currently supported: + + .Z compress + .gz gzip + .bz2 bzip2 + +Vim uses the mentioned programs to do the actual compression and +decompression. You might need to install the programs first. + +============================================================================== + +Next chapter: |usr_24.txt| Inserting quickly + +Copyright: see |manual-copyright| vim:tw=78:ts=8:noet:ft=help:norl: |