a technical how to

Charles Swiger cswiger at mac.com
Tue Dec 9 09:56:32 PST 2003

On Dec 8, 2003, at 8:51 PM, homeyra g wrote:
> Here is the question: How to truncate a file from the
> begining to a certain point in the file?

The question is whether this file is ASCII text so line-based tools 
(such as tail) work, or whether you are truncating a binary file, in 
which case "split -b" is probably a better bet.

If you've got a logfile named /var/log/messages, and you want to 
truncate that to the last 100 lines:

mv /var/log/messages /var/log/messages.$$
tail -100 < /var/log/messages.$$ > /var/log/messages
rm -f /var/log/messages.$$

Use "wc -l" and "grep -n" to identify where to truncate the file if 
it's not a fixed size that you want...


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