How can I edit a large file in place?

Question

I have a few files sized > 1 GB each. I need to remove last few bytes from the files. How can I do it? I prefer to edit file in place to save disk space.

I am on HP-UX.

Solution 1

Try using hexedit I haven't tried it on HP-UX but it should work. It allows you to move to a location in a file and truncate. I'm pretty sure that it does not read the whole file in but just seeks to the appropriate location for display.

Usage is fairly simple once you have launched it the arrow keys allow you to move around. F1 gives help. Ctrl-G moves to a location in the file (hint: to move to end use the size of the file from the bottom row of the display). Position the cursor on the first byte that you want to truncate and then press Escape T once you confirm the truncate will have been done. Ctrl-x exits.

Solution 2

Cut 2 kilobytes from end of file:

truncate -s-2K file

Solution 3

Use a tool that gives you access to the truncate system call. You can do it with only POSIX tools. Warning, typed into a browser; be especially careful as dd is even more unforgiving of errors than the usual unix command. 123456 is the number of bytes to keep.

dd if=/dev/null of=/file/to/truncate seek=1 bs=123456

A Perl version is much more readable:

perl -e 'truncate "$ARGV[0]", 123456 or die $!' /file/to/truncate

Solution 4

You can use dd for example:

dd if=yourfile of=outname bs=4k count=thefirstX4kb

Solution 5

You can use split or ed, awk or any programming language.

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Comments

[Admin]

I think vim has a 4G limit (could be wrong) but I don't think it does it in place (could be wrong).

[Admin]

@xenoterracide: I don't have vim here :-( and vi gives "Tmp file too large" Error.

[Admin]

@Hernant: That message tells you all you need to know about editing in place: vi is trying to copy it over to /tmp to work on. I think vim will do the same thing, and it does like to create a backup in the same directory.

[Hemant]

Thanks for your response. I prefer to edit file in place to save disk space. If nothing helps I will use dd :-).

[Hemant]

Thanks for your response. I prefer to edit file in place to save disk space and memory.