Extremly short introduction to bash

Bash is one of several shell interpreters. Other shells you can meet are: sh, csh, tcsh, zsh, ash, etc... The bash shell is the default standad shell on most gnu/linux based systems and basic commands are however almost same across all the shell variants.

Shell is the direct interface between the user and the system kernel.

Task 1. Open any terminal application - gnome-terminal, kterm, xterm. You will, most probably, be greeted by bash prompt

r0:~>

Basic shell commands

whoami

kdo jsem?

pwd

print working directory

ls

list working directory

ls -l

detailed list of working directory

cd

change directory

cp

copy files

mv

move files

rm

delete file

If the command is not recognized as shell command, then the folders in the enviroment variable PATH are searched for an executable with that name.

Hint. Help can be obtained using commands man, info, apropos. Try for instance

$ man man
$ apropos math

Hint. Further help can be obtained using commands fortune, cowsay.

 $ fortune | cowsay
 ________________________________________
/ Tuesday After Lunch is the cosmic time \
\ of the week.                           /
 ----------------------------------------
        \   ^__^
         \  (oo)\_______
            (__)\       )\/\
                ||----w |
                ||     ||

Remote connection - ssh

Task 2. Use ssh utility to connect to a remote system.

machine:~> ssh -C -Y your_login@r0.karlin.mff.cuni.cz

Sending signals and process management

Every running program can be in the state running or suspended. With respect to a shell it can be in the foreground or background.

jobs

list jobs started from given shell with their shell ids

fg

send job to foreground

bg

send job to background, this is equivalent to starting the job by job_command &

Every well behaved job listens to signals.

ps

list all your jobs with their process ids

kill jobid

send terminate signal to a job, job id can be its process id or its shell id (including %)

kill -9 jobid

change directory

Pressing following control keys will send signal to the foreground job

^C

terminate signal

^Z

suspend signal

^D

end of input signal

Cluster job queues usage

qstat

status of the computational queue

qsub -I -q queue1 -l nodes=1:ppn=1

open an interactive session with 1 cpu

More details on snehurka web