I have tried to use nice values, because I want to run some commands faster.
Anyway, I don't know how to use it.
e.g I have tried to use it like this:
nice +18 grep 'something' *.cpp
But I get error: file not found?
Can I use it like above? It would be creat help, because some commands I run takes lot of time.
Read the manpages for nice(1)
You need to use the -n option to specify the nice value. You'll also find that you're making the process more nice (which I am pretty sure is not what you want). Note that you need to be root to specify negative nice increments.
Also: Making your grep command less nice may or may not improve performance. If the process is CPU bound, you may see an improvement. If the process is disk I/O bound, you may see little or no improvement.
Thanks for advice anomie.