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.
3
5 Answers
Cut 2 kilobytes from end of file:
truncate -s-2K file 
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.
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 answered Aug 26, 2010 at 23:50
Gilles 'SO- stop being evil'
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You can use dd for example:
dd if=yourfile of=outname bs=4k count=thefirstX4kb 
- 1Thanks for your response. I prefer to edit file in place to save disk space. If nothing helps I will use dd :-).Hemant– Hemant2010-08-26 10:28:31 +00:00Commented Aug 26, 2010 at 10:28
You can use split or ed, awk or any programming language.
- Thanks for your response. I prefer to edit file in place to save disk space and memory.Hemant– Hemant2010-08-26 17:31:16 +00:00Commented Aug 26, 2010 at 17:31
vimhas a 4G limit (could be wrong) but I don't think it does it in place (could be wrong).