unexpected vi behavior

[michaelvv]

In AIX, after deleting all the lines from a file and saving, I and up with a one byte file containing a new line character. I expected to end up with a zero byte file, the same as in Linux or Solaris. This behavior is causing ‘test –s’ not to produce the desired results.

 

[RodKnowlton]

If you want a zero byte file, "cp /dev/null filename" is the way to go.

vi is, at its heart, a line editor. Its concept of an empty file is one with a single, empty line. Even if you create a zero byte file by other means, if you open it in vi and immediately write it without making any edits, you'll see that it now has a newline in it.

If you really need to do it with an editor, install vim. Vim will allow you to truly delete everything in the file, including that last newline.

- Rod


IBM Certified Advanced Technical Expert pSeries and AIX 5L
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[michaelvv]

Thanks Rod, but I'm not sure I totally agree. Of all the UNIX flavors that I have worked with (System V, SCO, Solaris, Linux and AIX), only AIX behaves this way. I am porting an application from Solaris and fortunately it is not a major inconvenience to add code to truncate the files where need be. Installing vim is not an option, these are production servers and I do not have 'root' access. Even if I did, obtaining all the approvals would be a major headache.

 

[RodKnowlton]

Thanks for the correction, michaelvv.

I'll bet my first encounter with vi and empty files was on AIX and I've avoided it since.

Here's an even odder behaviour: ex, which according to "ls -il" is the exact same executable as vi, doesn't append the newline to an empty file and also completely empties a file with ":1,$d".

- Rod

 

[michaelvv]

Rod,

That is absolutely bizzare! I had never used ex by itself, only from within vi. Not that I didn't trust you, but I had to see it for myself, and it is exactly like you say it is! Just for the heck of it, I also tried view, edit and vedit. edit also saved an empty (zero byte) file.

It is not exactly clear, but do you work for IBM? Are you in a position to suggest that they 'fix' it?

Thanks,
Mike

 

[RodKnowlton]

Mike,

Nope, I don't work for IBM.

Since vi has behaved that way since at least AIX 3.2.5, I'm guessing they're stuck keeping it "bugwards" compatible at this point.

- Rod