Processes in UNIX

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Think linear
 what operations do I want to perform
 what input/output do the tools use/provide




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  shell

          Userspace
                      root access
            Kernel

system
          Hardware
 calls



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what happens to the program?




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init

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cat test.txt | grep “hello”




      cat


            cat               grep


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Signal Name   Number   Meaning




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ps <flags> <list>
top
           u
kill <signal> <pid>

      kill -9 emacs




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top




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Stop! I didn’t want to do that!!




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ptree <user>




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 jobs, fg, bg, stop, notify

Jobs




 ‘&’         emacs &


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fg   bg




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So what if you have a massive job on a
multiuser machine and dont want to clog it up
for others?
           nice

nice <increment> <process>




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....daemons




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               cron


crontab.cron



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cron.allow    cron.deny
/var/spool/cron    etc/crond.d




crontab crontab.cron




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What does the cron entry look like?




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                      at



at <time> <process>




                       batch




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