Trim a file on HP_UX

Suppose you want to remove first 100 lines of a file named mail.log
First take the backup of the original file.
Check line count
#cat mail.log | wc –l
155
#cat mail.log | sed ‘1,10d’ >/tmp/mail_new.log
If you check the line count of newly created file mail_new.log
#cat mail_new.log | wc –l
145
Now you can rename mail_new.log with mail.log after taking the backup of original mail.log