hpr-knowledge-base/hpr_transcripts/hpr1724.txt

Episode: 1724
Title: HPR1724: Vim Hints 002
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1724/hpr1724.mp3
Transcribed: 2025-10-18 08:16:44

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This is HPR episode 1,724 entitled Vim Hints 2. It is hosted by Dave Morris' and is about 26 minutes
long. The summary is hints and tips for Vim users part 2. This episode of HPR is brought to you by
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Hello everyone. This is Dave Morris with another HPR episode. Today I'm continuing with my series
about Vim. I'm calling it Vim Hints because what I'm hoping to do is to give you a sort of a
survival guide in the ways of Vim. I've entitled this episode Vim at my homework and it's about
how you avoid losing stuff when you're working with Vim. I appreciate that we haven't really
started looking at how to use Vim yet to do anything but I thought it would be good as part of
the survival guide toolkit to look at the security angle of it first of all so that when you do
get to actually use it you can do this with the knowledge that you've got within pretty secure.
One of the first things that you can do is to ensure that Vim is running in the mode where it
keeps the backup of what you're editing and to do that you need to set up a configuration file.
I mentioned this in the last episode. I think I mentioned that normally the configuration file is
called .VimRC and it's in the home directory. That's certainly one of the options that you have
and that shadows the way things used to be done under VI but there's an alternative which is to
create a directory, top-level directory only home directory called .Vim and then to create a file
called VimRC without the dot on the front in that directory. You choose which one you prefer.
This is for Linux of course. If you're on Windows it's called underscore VimRC and so on.
I'm not really going to go into this. I'm not a Windows user. I don't know about Windows. You can
find out more about it in the documentation if you need to do this. Anyway, I prefer to keep my
configuration file in the top-level directory just because I guess I'm stuck in my ways.
That's a way I've always done it. The very existence of this file makes the program that's
sometimes invoked as VI behave as if it's Vim but it's a good idea to switch on all of the Vim
features by explicitly setting the no compatible option. All you need to do to achieve this is to
put a line in the configuration file which consists of set, space, in or compatible, no compatible.
In other words switch off VI compatibility. You appreciate that Vim has come from VI and it will
emulate it if you wish it to. You can't really think why you'd want to but you can if you want to.
Having got that out of the way, the thing I was talking about earlier, the backup thing.
is enabled by on the next line putting set, space, backup. Now backup file is a copy of the file
that you're editing which is taken before you actually make any changes so you've got something
to fall back on. The backup file is saved in the same directory as file being edited by default.
Personally I think this is the best way of doing things but you can if you wish tell Vim to put
your backups in a different place and there's a command you can add to the configuration file.
These are on the show notes by the way which will enable you to do this. Set backup
B-A-C-K-U-P-D-I-R equals and then you follow that with a list of directories. You could if you wanted to
put a tilde meaning home slash dot backup so if you'd created a dot backup directory at the top
level then it would write your backup files in there. The example shows that being followed by
comma dot which means the current directory. If you haven't got backup directory that means
and comma slash TMP so if you don't have a home directory which might be the case if you're
running off a disk which is not writable then try and write the backup into the temp directory.
So I wouldn't personally suggest you do this just now. Just get everything to be written into
the same directory as the file itself. I would suggest is the best way of going ahead.
So the next topic in the sort of securing things section is to talk about undoing changes.
So you might want to know how to do this. You might do something silly like delete great block of
text from your file so or you might make a change in the wrong place or you might do something.
There's many things you can do. We'll come on to some of the some of the large and powerful
features of them but of course large and powerful means you can make some pretty horrendous errors.
So if you do make a mistake then you can undo the change. If you're in normal mode remember we
talked about normal mode the mode you normally start up in and the one that you return to by
pressing escape. When you're in that mode typing you will undo the last change. There's also a
redo so if you undead did something and realized no actually that's what I did want to do you can
hold down control key and press R normally call control R and it will redo the last change.
So Vim is actually keeping a record of these changes. It's keeping many of them. You can control
how many but we won't go into that just now and you can undo successive changes back in time
and control R redoes the the undun changes forward in time. It can get a lot more complicated than
this because if you think about it you can undo a thing make a change and then undo that and so
you end up with a sort of tree structure of things you've done things you could undo and things
you could redo. It can get quite complex and we'll maybe look at this in a later episode.
Personally I don't do I've not really bothered with this much myself so less it sort of seems
to be appropriate I'll maybe not get to that but we'll see we'll see. I'm going to play this by
year largely and if I get feedback asking for particular me to go into a particular directions
then I will do that. So one of the things you you can do with Vim and it's quite good to do this
I believe anyway is that you can retain your undo history between editing sessions. So there's
thing called an undo file which holds the change history and what's more you can put that in
a directory specifically for this purpose so it keeps an undo file in there in this directory
and I've given examples for how to do this you need to create the undo directory first
and in my particular case I've put it under the dot Vim directory I mentioned earlier
so you would put in your configuration file the line set space undo dir
i-u-n-d-o-d-i-r equals and then tilde slash dot Vim slash undo dir so that means I want my undo file
or files to be files plural to be put into this directory and then you'd follow that by enabling the
undo file option that is saving your undo history with the command set space undo file u-n-d-o-f-i-l-e
now the consequence of this is that when you start an editing session it's possible for you to type
you as your first first thing you do what that means is assuming you've been editing this file before
it means undo the thing I did last time I was editing it that can be a little bit surprising
I certainly surprised myself by doing this but it is if you know what you're doing
quiet a powerful feature so things like you might apply a change into a program test the program
find having saved it that is then find oh hell that's that was rubbish I don't want to do that
go back start editing the file again press u and undo that change and you're back to where you
were before you you did the thing that you wish you hadn't so the next topic under this particular
heading keeping your files and your work intact is quite large subject of file recovery now there's
a lot here I won't go into a huge amount of detail I just wanted to give you a sort of
taster and it's enough to survive with there's references here that you can follow up if you
want to dig deeper so as Vim is running it has its own recovery mechanism where it generates
a what's called a swap file this file is normally under under unix and Linux under BSD and Linux
I really mean or indeed macOS it the file is the file name is built from the name the file being
edited with the dot propended to it making it a hidden file and with the extension dot SWP
being stuck on the end so if you're editing the file test file the swap file would be called
dot test file dot SWP and it's in the same directory as the file you're editing you can
make Vim write swap files elsewhere and there's something to be said for this you could put it on
a different partition so that you're safer from problems and crashes you can also switch it off
that the whole swap file business but that's not smart not a smart thing to do I would say and I
would suggest leaving things in the default mode until you understand more about about this
and the swap file is updated that's keeping history of what's going on it's updated after typing
200 characters or when you've not typed in anything for four seconds when you finish editing
when you write your results or indeed quit out of it out of them then swap files deleted so it's
a thing that's present while you're editing and it's holding a recovery information about the
edits that you have done so the issue of recovery is really the the big issue here what recovery
is offering you is the ability to recover from something nasty happening like the power going
out or your machine crashing for whatever reason I have been known to open up a ssh session to
another machine and then shut it down forgetting that I've actually got an editor running
on it or indeed shut down the machine there's all manner of dark things that one can do to cause
problems if something happens to crash your vim session then your swap file will be left behind
and if you know that's the case you know that something's gone horribly wrong then you can
just simply invoke vim in its recovery mode to start the recovery process and you do that by
typing vim space minus r space and then the file name you will see the recovery process will
will be invoked you'll see a message of the sort that I've included in the show notes it says
using swap file in the name of the swap file original file gives you the name the original file
recovery completed tells you to check that everything's okay and so on and so forth and then you
can carry on with your editing session now the key issue is that it doesn't delete the swap file
the swap file is still there we'll come on to that in a minute now the vim minus r r thing is
is fine personally I don't use it very often I tend to just go and do the alternative thing which is
to go back to editing the file I was editing before and that's the point at which
vim will say oh there's a swap file here and we'll alert you now you'll see in the show notes
an example of the sort of message you'll get which starts with e325 colon attention
says I found a swap file it gives you the name of the swap file gives you details about when
when it was created what file you were editing and then there's a key very key piece of information
modified and in an example I've given you here yes you might see modified no that means you
hadn't changed anything then since you last saved your file so this case modified yes is the
critical one so it then warned you that you could see the same consequences you could see the
same situation if somebody else is editing the file well you indeed were opening it had opened
and we're editing the same file in another window or something that's a possibility that's another
that's one reason why they might be a swap file but the most likely thing is that the edit is
crashed and this is it's offering you the option of recovering so you'll get a a message saying
what do you want to do you want to open it read only edit it regardless recover delete it delete
the swap file that is quit abort that's assume that you have got a crashed edit session
you see them the message that there are modifications you want to do the recovery all you need to do
to press R and the recovery will go ahead and it's the you get the same message as you would have
got if you type VIN minus R and the file name now here's the thing about the swap file
it's not deleted it's used for the recovery purposes but it is not deleted in fact the edit session
creates a new swap file in fact the the new swap file will have the extension dot SWO instead of
SWP and then keeps on cycling through the last letter of this extension until it runs out
seems slightly off anyway it goes all the way back to a so if you if you imagine you've got the
situation where you have just recovered and you have said okay recover you've recovered the
changes you've now got your file back to the state it was with unsafe changes in it so you would
type colon wq as we talked about in the last episode which writes the output and quits the edit now
if you do this you will have exited everything will be safe and fine but there will still be
a swap file left from the crash session if you then go back a bit later on and edit the same file again
you will find that VIN comes back with the e325 message saying I found a swap file but it will it will
warn you that the file that it that you're editing is newer than the swap file in other words
something weird has happened as far as VIN is concerned and the file has changed now all
that's happened is the swap file has not been deleted so you can at that point at the prompt
that I mentioned earlier use d to delete the file the only thing about this is that it can be
confusing I find it confusing sometimes you've done the recovery you think everything's fine you've
done further editing you've saved your file you've gone off done something else you come back
right I'm going to edit my file again you edit it and it comes back and says I found a swap file
and you think in what oh oh that's that old swap file from before right I'll just delete it that
seems a bit counterintuitive to do it that way so I've offered you two other ways of dealing with
this you realize that this is VIN being very very very cautious and not deleting the recovery file
all on its own what you could have done is you could have quit saved your file and quit out of
the editor and then knowing that there was a swap file you could have removed it yourself
in the example I've shown you in the show notes I'm assuming that you file in question is called
test file 2 therefore there's a swap file called dot test file 2 dot SWP where you could simply
RM that file get rid of it having recovered it but that's also messy the third possibility is
you recover you write the changed file out to make everything secure then you don't quit from them
you type the command colon e what colon e does is it tells me to re-edit the file you're already
working with in other words it it starts again as if the file has just seen the file and in doing so
it checks to see if there's a swap file left around and it says oh yes there's a swap file over
there it gives you the warning that there's a there's a recovery file but it's that the file
that you're editing is newer than the recovery file so you can then type the D command and come out
and delete the swap file and then quit the edit and it did continue to do the editing if you want to
personally I think option 3 is the more logical thing to do but you will need to choose
the route through this that you prefer for yourself but I'm raising this because it is one of
the slightly weird aspects of them that catches people out when they're new to using it
in the show notes I want to talk about the case where there are no changes in the swap file
instead of it saying modified yes you get the message modified no so the swap file is not needed
you don't need to recover anything because there was nothing to recover so you can just press D
at the prompt open read only edit anyway etc and you can then continue editing the file as normal
and you know at that point that the swap file has been deleted and everything is fine and dandy
so hopefully the show notes will help you to get your head around this really I made
sort of introduced this quite early and it might be confusing me doing it that way but I thought
if you had this as a thing to refer to later on as you use VIM that you will find it
helpful to refer back so I've added the comment that they make in the VIM manual which is
don't panic the recovery thing is a little bit weird but it's pretty robust and we'll
get you out of nasty situations where your machine has crashed or something else nasty has happened
so I finish up my show notes with the summary of the changes you should make to the configuration
file I've just listed them all there together and reminding you that you in normal mode will
undo a change control R in normal mode will redo a change that you've previously undone
and don't forget that restarting VIM after a crash will invoke a recovery dialogue which we've
just been discussing so I hope that's useful and the next episode in this series we will start using
VIM for proper and for real hope you find that useful okay bye
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