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I. Useful commands

Investigate the man pages for these handy commands and/or ask your instructor for a demo.

alias
enscript
wc
sort
less
which
grep
grep -H -r "words to find" *
[locate] (not available on all machines)

ctrl-z & fg
ps aux | grep username
kill -9 #
top

II. The best thing since sliced bread: screen

Screen is useful anytime you want to be able to start a job, disconnect from the machine running it, then reconnect to the machine and the job later. For example, maybe you have to go home for dinner and want to be able to start a program running, log out, go home, and log in later from home to check on the program. Alternatively, maybe you're working on a flaky wireless connection and you want to be able to start a program running with the peace of mine that you can get back to it if your connection goes down while it's running. In both cases, the solution is to start a "screen" -- a terminal window that can be detached and reattached to different physical terminals. The basic sequence is to type "screen", then a series of commands that starts your program, then ctrl-a d to detach, then later "screen -dR" to reattach. More complicated options are explained in the man pages.

If your processes run under "screen" are slowing down:

  1. On whatever machine you want to run the job, create a new PAG by running "pagsh -c /bin/tcsh" PAG stands for process authentication group. This way you can start a set of processes that share the same authentication token and they are isolated from your other processes.
  2. start a new screen session
  3. run "reauth" You will be prompted for your password, which will be used to renew your tokens periodically. Remember the PID that reauth tell you, or figure it out later using "ps aux | grep youronyengoeshere"
  4. start python and run job
  5. detach by ctrl-a d and log out (which leaves that pagsh)
  6. later reconnect with a new login (which obviously doesn't know about the old pagsh) and screen -dR
  7. When you are done, kill the PID and exit out of screen and pagsh.

III. Linux scripting

Linux can be used as a programming language as well as an operating system -- this is called linux scripting. Most linux scripting capabilities can be accomplished in python, but with reduced efficiency.

This optional linux scripting tutorial is best completed after you are comfortable with both linux and the basics of programming in any language. The tutorial goes with this bashscriptingsolutions directory and this bashscriptingfinal directory.