List Certain Output

Shell Programming and Scripting
1

Hi Expert,

I have a text file that contain the following data

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root      1397  0.0  0.0      0     0 ?        S<   Jul14   0:00 [aio/28]
john      1398  0.0  0.0      0     0 ?        S<   Jul14   0:00 [aio/29]
john      1399  0.0  0.0      0     0 ?        S<   Jul14   0:00 [aio/30]
ruby         7  0.0  0.0      0     0 ?        S<   Jul14   0:00 [watchdog/1]
root         8  0.0  0.0      0     0 ?        S<   Jul14   0:01 [migration/2]
jane         9  0.0  0.0      0     0 ?        SN   Jul14   0:00 [ksoftirqd/2]
john        10  0.0  0.0      0     0 ?        S<   Jul14   0:00 [watchdog/2]
root        11  0.0  0.0      0     0 ?        S<   Jul14   0:01 [migration/3]

Now, what I want is to list just user john and ruby with certain header, e.g:

USER       PID %CPU %MEM     TTY    STAT TIME COMMAND
john      1398  0.0  0.0      0     0 ?        S<   Jul14   0:00 [aio/29]
john      1399  0.0  0.0      0     0 ?        S<   Jul14   0:00 [aio/30]
ruby         7  0.0  0.0      0     0 ?        S<   Jul14   0:00 [watchdog/1]

How do I do that? with awk?

Thank you Expert.

2 
$ egrep "^USER|^john|^ruby" infile
3 
$ nawk '/USER|john|ruby/' filename
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
john      1398  0.0  0.0      0     0 ?        S<   Jul14   0:00 [aio/29]
john      1399  0.0  0.0      0     0 ?        S<   Jul14   0:00 [aio/30]
ruby         7  0.0  0.0      0     0 ?        S<   Jul14   0:00 [watchdog/1]
john        10  0.0  0.0      0     0 ?        S<   Jul14   0:00 [watchdog/2]