I'm using this command:
sar 1 | tail -n +3
which outputs the following (every 1 second, I interrupted it after few seconds):
root@debian:/home/hyper/stats# sar 1 | tail -n +3
20:00:04 CPU %user %nice %system %iowait %steal %idle
20:00:05 all 0,25 0,00 0,50 0,00 0,00 99,25
20:00:06 all 0,50 0,00 0,25 0,00 0,00 99,25
20:00:07 all 4,79 0,00 1,01 0,00 0,00 94,21
20:00:08 all 0,75 0,00 0,75 0,75 0,00 97,74
20:00:09 all 1,26 0,00 0,76 0,00 0,00 97,98
20:00:10 all 0,75 0,00 0,50 0,00 0,00 98,74
^C
The problem is when I try to write this output to file. I tried with:
sar 1 | tail -n +3 > file
But it creates an empty file. The problem is the "sar" command that generates a "continuous output", but I don't know how to handle it.
EDIT: to clarify what I want to do: "I run a command, like "top" (or "sar 1" etc.), which produces an output every X seconds. Every produced output contains an header (few lines) that I don't want. So I want to run "top" for 10 seconds and save the 10 produced outputs without their headers to a file."
Instead of using tail, you can use a shell command list to strip out the first few lines:
sar 1 | { read; read; cat; } > file.txt
I'm not sure why tail is not working; I though perhaps you were just missing the -f option, but that doesn't seem to produce any output either.