230 lines
10 KiB
Text
230 lines
10 KiB
Text
*recover.txt* For Vim version 7.4. Last change: 2010 Jul 20
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VIM REFERENCE MANUAL by Bram Moolenaar
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Recovery after a crash *crash-recovery*
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You have spent several hours typing in that text that has to be finished
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next morning, and then disaster strikes: Your computer crashes.
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DON'T PANIC!
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You can recover most of your changes from the files that Vim uses to store
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the contents of the file. Mostly you can recover your work with one command:
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vim -r filename
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1. The swap file |swap-file|
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2. Recovery |recovery|
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==============================================================================
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1. The swap file *swap-file*
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Vim stores the things you changed in a swap file. Using the original file
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you started from plus the swap file you can mostly recover your work.
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You can see the name of the current swap file being used with the command:
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:sw[apname] *:sw* *:swapname*
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The name of the swap file is normally the same as the file you are editing,
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with the extension ".swp".
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- On Unix, a '.' is prepended to swap file names in the same directory as the
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edited file. This avoids that the swap file shows up in a directory
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listing.
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- On MS-DOS machines and when the 'shortname' option is on, any '.' in the
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original file name is replaced with '_'.
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- If this file already exists (e.g., when you are recovering from a crash) a
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warning is given and another extension is used, ".swo", ".swn", etc.
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- An existing file will never be overwritten.
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- The swap file is deleted as soon as Vim stops editing the file.
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Technical: The replacement of '.' with '_' is done to avoid problems with
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MS-DOS compatible filesystems (e.g., crossdos, multidos). If Vim
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is able to detect that the file is on an MS-DOS-like filesystem, a
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flag is set that has the same effect as the 'shortname' option.
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This flag is reset when you start editing another file.
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*E326*
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If the ".swp" file name already exists, the last character is
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decremented until there is no file with that name or ".saa" is
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reached. In the last case, no swap file is created.
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By setting the 'directory' option you can place the swap file in another place
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than where the edited file is.
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Advantages:
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- You will not pollute the directories with ".swp" files.
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- When the 'directory' is on another partition, reduce the risk of damaging
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the file system where the file is (in a crash).
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Disadvantages:
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- You can get name collisions from files with the same name but in different
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directories (although Vim tries to avoid that by comparing the path name).
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This will result in bogus ATTENTION warning messages.
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- When you use your home directory, and somebody else tries to edit the same
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file, he will not see your swap file and will not get the ATTENTION warning
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message.
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On the Amiga you can also use a recoverable ram disk, but there is no 100%
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guarantee that this works. Putting swap files in a normal ram disk (like RAM:
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on the Amiga) or in a place that is cleared when rebooting (like /tmp on Unix)
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makes no sense, you will lose the swap file in a crash.
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If you want to put swap files in a fixed place, put a command resembling the
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following ones in your .vimrc:
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:set dir=dh2:tmp (for Amiga)
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:set dir=~/tmp (for Unix)
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:set dir=c:\\tmp (for MS-DOS and Win32)
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This is also very handy when editing files on floppy. Of course you will have
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to create that "tmp" directory for this to work!
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For read-only files, a swap file is not used. Unless the file is big, causing
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the amount of memory used to be higher than given with 'maxmem' or
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'maxmemtot'. And when making a change to a read-only file, the swap file is
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created anyway.
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The 'swapfile' option can be reset to avoid creating a swapfile.
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Detecting an existing swap file ~
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You can find this in the user manual, section |11.3|.
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Updating the swapfile ~
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The swap file is updated after typing 200 characters or when you have not
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typed anything for four seconds. This only happens if the buffer was
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changed, not when you only moved around. The reason why it is not kept up to
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date all the time is that this would slow down normal work too much. You can
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change the 200 character count with the 'updatecount' option. You can set
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the time with the 'updatetime' option. The time is given in milliseconds.
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After writing to the swap file Vim syncs the file to disk. This takes some
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time, especially on busy Unix systems. If you don't want this you can set the
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'swapsync' option to an empty string. The risk of losing work becomes bigger
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though. On some non-Unix systems (MS-DOS, Amiga) the swap file won't be
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written at all.
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If the writing to the swap file is not wanted, it can be switched off by
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setting the 'updatecount' option to 0. The same is done when starting Vim
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with the "-n" option. Writing can be switched back on by setting the
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'updatecount' option to non-zero. Swap files will be created for all buffers
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when doing this. But when setting 'updatecount' to zero, the existing swap
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files will not be removed, it will only affect files that will be opened
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after this.
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If you want to make sure that your changes are in the swap file use this
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command:
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*:pre* *:preserve* *E313* *E314*
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:pre[serve] Write all text for all buffers into swap file. The
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original file is no longer needed for recovery.
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This sets a flag in the current buffer. When the '&'
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flag is present in 'cpoptions' the swap file will not
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be deleted for this buffer when Vim exits and the
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buffer is still loaded |cpo-&|.
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{Vi: might also exit}
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A Vim swap file can be recognized by the first six characters: "b0VIM ".
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After that comes the version number, e.g., "3.0".
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Links and symbolic links ~
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On Unix it is possible to have two names for the same file. This can be done
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with hard links and with symbolic links (symlinks).
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For hard links Vim does not know the other name of the file. Therefore, the
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name of the swapfile will be based on the name you used to edit the file.
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There is no check for editing the same file by the other name too, because Vim
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cannot find the other swapfile (except for searching all of your harddisk,
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which would be very slow).
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For symbolic links Vim resolves the links to find the name of the actual file.
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The swap file name is based on that name. Thus it doesn't matter by what name
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you edit the file, the swap file name will normally be the same. However,
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there are exceptions:
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- When the directory of the actual file is not writable the swapfile is put
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elsewhere.
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- When the symbolic links somehow create a loop you get an *E773* error
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message and the unmodified file name will be used. You won't be able to
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save your file normally.
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==============================================================================
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2. Recovery *recovery* *E308* *E311*
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Basic file recovery is explained in the user manual: |usr_11.txt|.
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Another way to do recovery is to start Vim and use the ":recover" command.
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This is easy when you start Vim to edit a file and you get the "ATTENTION:
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Found a swap file ..." message. In this case the single command ":recover"
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will do the work. You can also give the name of the file or the swap file to
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the recover command:
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*:rec* *:recover* *E305* *E306* *E307*
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:rec[over] [file] Try to recover [file] from the swap file. If [file]
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is not given use the file name for the current
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buffer. The current contents of the buffer are lost.
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This command fails if the buffer was modified.
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:rec[over]! [file] Like ":recover", but any changes in the current
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buffer are lost.
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*E312* *E309* *E310*
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Vim has some intelligence about what to do if the swap file is corrupt in
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some way. If Vim has doubt about what it found, it will give an error
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message and insert lines with "???" in the text. If you see an error message
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while recovering, search in the file for "???" to see what is wrong. You may
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want to cut and paste to get the text you need.
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The most common remark is "???LINES MISSING". This means that Vim cannot read
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the text from the original file. This can happen if the system crashed and
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parts of the original file were not written to disk.
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Be sure that the recovery was successful before overwriting the original
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file or deleting the swap file. It is good practice to write the recovered
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file elsewhere and run 'diff' to find out if the changes you want are in the
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recovered file. Or use |:DiffOrig|.
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Once you are sure the recovery is ok delete the swap file. Otherwise, you
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will continue to get warning messages that the ".swp" file already exists.
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{Vi: recovers in another way and sends mail if there is something to recover}
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ENCRYPTION AND THE SWAP FILE *:recover-crypt*
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When the text file is encrypted the swap file is encrypted as well. This
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makes recovery a bit more complicated. When recovering from a swap file and
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encryption has been used, you will be asked to enter one or two crypt keys.
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If the text file does not exist you will only be asked to enter the crypt key
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for the swap file.
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If the text file does exist, it may be encrypted in a different way than the
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swap file. You will be asked for the crypt key twice:
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Need encryption key for "/tmp/tt" ~
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Enter encryption key: ****** ~
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"/tmp/tt" [crypted] 23200L, 522129C ~
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Using swap file "/tmp/.tt.swp" ~
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Original file "/tmp/tt" ~
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Swap file is encrypted: "/tmp/.tt.swp" ~
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If you entered a new crypt key but did not write the text file, ~
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enter the new crypt key. ~
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If you wrote the text file after changing the crypt key press enter ~
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to use the same key for text file and swap file ~
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Enter encryption key: ~
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You can be in one of these two situations:
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1. The encryption key was not changed, or after changing the key the text file
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was written. You will be prompted for the crypt key twice. The second
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time you can simply press Enter. That means the same key is used for the
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text file and the swap file.
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2. You entered a new encryption key, but did not save the text file. Vim will
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then use the new key for the swap file, and the text file will still be
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encrypted with the old key. At the second prompt enter the new key.
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Note that after recovery the key of the swap file will be used for the text
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file. Thus if you write the text file, you need to use that new key.
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vim:tw=78:ts=8:ft=help:norl:
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