Bash in theory and in practice - part one

bashin theory and in practice

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AgendaGeneral InfoUnderwaterOverviewSyntaxExamples

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AgendaGeneral InfoUnderwaterOverviewSyntaxExamples

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19.06

03.07

bashbourne again shellGNU projecttextual shell

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interface of an O. S.to access Kernel services

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shellbash

. resources control

. process execution

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o.s.shellbash

. process manager

. memory manager

. scheduler/event manager

. file manager

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o.s.shellbash

. process wrapper

. scheduler controll

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kernelo.s.shellbash

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kernelo.s.

shellbash

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kernelo.s.

shellbash

Desktop PC, Parallel Systems, Distribuited Systems, Clustered Systems, Real-time Systems, Embedded Systems

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kernelo.s.

shellbash


Monolithic, MicroKernel, Hybryd kernel, exoKernel

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kernelo.s.

shellbash


Monolithic, MicroKernel, noKernel, Hybryd kernel, exoKernel

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kernelo.s.

shellbash


Monolithic, MicroKernel, Hybrid kernel, exoKernel

textual, GUI

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kernelo.s.

shellbash


Monolithic, MicroKernel, Hybrid kernel, exoKernel

textual, GUI

sh, csh, ksh, bash, tcsh, zsh

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shell 1970: runcom (Multics) JCL (s/390)

1975-1978: Steve Bourne, at Bell Labs wrote sh1978-1979: Bill Joy at BSD wrote csh

1981: tcsh is a fork of csh POSIX compliance1983: David Korn wrote ksh

1989: Brian Fox wrote bash1990: Paul Falstad wrote zsh1997: bash 2.02004: bash 3.02011: bash 4.2 latest (now) stable

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bash

UnderWater

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bash Pick-Up a Mac OS X Box

UnderWaterTerminal Processbash-3.2$ ps -ef|grep Terminalps -ef|grep Terminal 501 1636 211 0 1:55pm ?? 0:04.57 /Applications/Utilities/Terminal.app/Contents/MacOS/Terminal -psn_0_667811

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bash-3.2$ ps -ef| grep 1636ps -ef| grep 1636 501 1636 211 0 1:55pm ?? 0:05.87 /Applications/Utilities/Terminal.app/Contents/MacOS/Terminal -psn_0_667811 0 1638 1636 0 1:55pm ttys000 0:00.03 login -pfql valeriobalbi /bin/bash -c exec -la bash /bin/bash

Login Process

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bash-3.2$ ps -ef| grep 1636ps -ef| grep 1636 501 1636 211 0 1:55pm ?? 0:05.87 /Applications/Utilities/Terminal.app/Contents/MacOS/Terminal -psn_0_667811 0 1638 1636 0 1:55pm ttys000 0:00.03 login -pfql valeriobalbi /bin/bash -c exec -la bash /bin/bash

bash-3.2$ ps -ef| grep 1638ps -ef| grep 1638 0 1638 1636 0 1:55pm ttys000 0:00.03 login -pfql valeriobalbi /bin/bash -c exec -la bash /bin/bash 501 1639 1638 0 1:55pm ttys000 0:00.11 -bash

Login Process

Shell Invocation

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bash Pick-Up a Linux Box

UnderWater

[root@www ~]# ps -ef|grep sshdroot 3065 1 0 Feb05 ? 00:01:54 /usr/sbin/sshdroot 10442 3065 0 17:15 ? 00:00:00 sshd: root@pts/0

[root@www ~]# ps -ef| grep 10442root 10442 3065 0 17:15 ? 00:00:00 sshd: root@pts/0 root 10464 10442 0 17:15 pts/0 00:00:00 -bash

SSH Process and Login

Shell Invocation

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bash Who said system to invoke bash

UnderWater

[root@www ~]# cat /etc/passwd|head -5root:x:0:0:root:/root:/bin/bashbin:x:1:1:bin:/bin:/sbin/nologindaemon:x:2:2:daemon:/sbin:/sbin/nologinadm:x:3:4:adm:/var/adm:/sbin/nologinlp:x:4:7:lp:/var/spool/lpd:/sbin/nologin

Linux Users Definitions

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UnderWater

[root@www ~]# cat /etc/passwd|head -5root :x :0 :0 :root :/root :/bin/bashbin :x :1 :1 :bin :/bin :/sbin/nologindaemon :x :2 :2 :daemon :/sbin :/sbin/nologinadm :x :3 :4 :adm :/var/adm :/sbin/nologinlp :x :4 :7 :lp :/var/spool/lpd :/sbin/nologin

Username Password UID GID Description Home Initialprogram


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UnderWater



[root@www ~]# grep root /etc/shadowRoot: $1$LDqgrtQA$IXip/e.HuPhjSjLWXmrdj0 :15561 :0:99999:7:::

Username Password Lastchanged PasswordAging


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UnderWater





[root@www ~]# cat /etc/passwd|head -1root:$1$LDqgrtQA$IXip/e.HuPhjSjLWXmrdj0:0:0:root:/root:/bin/bash


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UnderWater





[root@www ~]# cat /etc/passwd|head -1root::0:0:root:/root:/bin/bash


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UnderWater




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UnderWater



[root@www ~]# ls -l /etc/shells-rw-r--r-- 1 root root 60 15 feb 2012 /etc/shells


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UnderWater



[root@www ~]# ls -l /etc/shells-rw-r--r-- 1 root root 60 15 feb 2012 /etc/shells

[root@www ~]# cat /etc/shells/bin/sh/bin/bash/sbin/nologin/bin/tcsh/bin/csh/bin/ksh


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bash the way to suit your bash

UnderWater

[root@www ~]# ls -l /etc/profile-rw-r--r-- 1 root root 1029 21 set 2009 /etc/profile[root@www ~]# ls -l /root/.bash_profile-rw-r--r-- 1 root root 191 6 gen 2007 /root/.bash_profile

what after login?

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UnderWater


[root@www ~]# ls -l /etc/profile.d/totale 104-rwxr-xr-x 1 root root 766 21 lug 2011 colorls.csh-rwxr-xr-x 1 root root 727 21 lug 2011 colorls.sh-rwxr-xr-x 1 root root 3015 19 ago 2011 lang.csh-rwxr-xr-x 1 root root 3466 19 ago 2011 lang.sh…

what after login?

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UnderWater



[root@www ~]# ls -l /root/.bashrc-rw-r--r-- 1 root root 176 6 gen 2007 /root/.bashrc

[root@www ~]# ls -l /etc/bashrc-rw-r--r-- 1 root root 1708 21 set 2009 /etc/bashrc

what after login?

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UnderWater





what after login?1

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UnderWater





what after login?1

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for i in /etc/profile.d/*.sh ; do if [ -r "$i" ]; then if [ "$PS1" ]; then . $i else . $i >/dev/null 2>&1 fi fidone

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UnderWater





what after login?1

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if [ -f ~/.bashrc ]; then. ~/.bashrc

fi

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UnderWater





what after login?1

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3

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# Source global definitionsif [ -f /etc/bashrc ]; then

. /etc/bashrcfi

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bash

Overview

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bash POSIX 1003.1 standard (IEEE Std 1003.1)pazh-ics not poh-six

Command InterpreterDefault 4 Linux and Mac OS XBourne Again Shell ( as rebird or another Bourne)

A superset of Bourne shellInclude history and directory stack from C shellRelative New concepts in the recents versions: . 3.0 regex like in perl . 4.0 hash to implement awk

Overview

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bash OverviewFunction Implemented:

Command line editing Command line completion Unlimited size command history Prompt control Bash startup files The Directory Stack The Restricted Shell Bash POSIX Mode Bash conditional expressions

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bash Overview

[root@www ~]#set -o vi

Esc-k Esc-j

Function Implemented:


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bash Overview

[root@www ~]#set -o vi

Esc-k Esc-j

beginning-of-line (C-a)end-of-line (C-e)forward-char (C-f)backward-char (C-b)forward-word (M-f)backward-word (M-b)clear-screen (C-l)



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bash Overview

[root@www ~]# ls /root/.bash



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bash Overview

[root@www ~]# ls /root/.bash +TAB+TAB.bash_history .bash_profile .bashrc



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bash Overview

[root@www ~]# ls /root/.bash +TAB+TAB.bash_history .bash_profile .bashrc

[root@www ~]# mkfs +TAB+TABmkfs mkfs.ext2 mkfs.ext3 mkfs.vfat



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bash Overview

export HISTFSIZE=10000

export HISTFILESIZE=10000shopt -s histappend



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bash Overview

$PS1 - primary prompt string, default \s-\v\$ .$PS2 - secondary, default is >$PS3 - prompt for the select command$PS4 - during an execution trace. default is +



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bash Overview

$PS1 - primary prompt string, default \s-\v\$ .$PS2 - secondary, default is >$PS3 - prompt for the select command$PS4 - during an execution trace. default is +

\d : date "Tue May 26" \h : hostname up to the first '.' \t : current time HH:MM:SS \u : username of the current user \w : current working directory \$ : if UID is 0, a #, otherwise a $



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bash Function Implemented:


Overview

/etc/profile/etc/profile.d/*

/root/.bash_profile/root/.bashrc/etc/bashrc

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Overview

[root@www ~]# dirs~[root@www ~]# pushd /etc/etc ~[root@www etc]# pushd /tmp/tmp /etc ~[root@www tmp]# popd/etc ~[root@www etc]# dirs/etc ~

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Overview

bash -rrbashbash --restricted

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Overview


vi:set shell=/bin/sh:shell

~$ rbash~$ cd /rbash: cd: restricted~$ bash~$ cd //$

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Overview


vi:set shell=/bin/sh:shell

~$ rbash~$ cd /rbash: cd: restricted~$ bash~$ cd //$

rssh

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Overview

- When a command in the hash table no longer exists, Bash will re-search $PATH to find the new location. This is also available with ‘shopt -s checkhash’.

- The message printed by the job control codeand builtins when a job exits with a non-zerostatus is ‘Done(status)’.

- The message printed by the job control code and builtins when a job is stopped is ‘Stopped(signame)’, where signame is, for example, SIGTSTP.

And other 42...

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Overview

to test $file

[ -e filepath ] true if file exists. [ -x filepath ] true if file exists and exec. [ -d filepath ] true if dir exists. [ expr1 -a expr2 ] and condition [ expr1 -o expr2 ] or condition

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Overview

to test $file

[ -e filepath ] true if file exists. [ -x filepath ] true if file exists and exec. [ -d filepath ] true if dir exists. [ expr1 -a expr2 ] and condition [ expr1 -o expr2 ] or condition

for arithmetics [ $VAR1 OP $VAR2 ] true if file exists. OP := -gt -eq -ne -lt -ge -le

AgendaGeneral InfoUnderwaterOverview

SyntaxScriptingExamples

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19.06

03.07

Bash in theory and in practice - part one

Technology

Transcript of Bash in theory and in practice - part one