SlideShare a Scribd company logo

Bash in theory and in practice - part two

Valerio Balbi, profile picture
Valerio Balbi

The document discusses the Bash shell, including its history, login process, main features, and syntax. It covers Bash basics like commands, functions, parameters, variables, redirections and scripting. Specific syntax like comments, quotes, loops, conditionals, arithmetic and logical expressions are examined in detail with examples. The document also explores Bash functions, curly braces and local variable definitions within functions.

Technology
1 of 79
Downloaded 35 times
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
bashin theory and in practice 19.06.2013 03.07.2013 @pvb265 #imolug
abstract 19.06.2013 03.07.2013 @pvb265 #imolug
abstract 19.06.2013 03.07.2013 @pvb265 #imolug shell bash kernel o.s. history
abstract 19.06.2013 03.07.2013 @pvb265 #imolug shell bash kernel o.s. Login Process history passwd shadow shells configurationfiles
abstract 19.06.2013 03.07.2013 @pvb265 #imolug shell bash kernel o.s. Login Process history passwd shadow shells configurationfiles Main Features POSIX completion cmdhistory
AgendaGeneral Info Underwater Overview Syntax Example 19.06.2013 03.07.2013 @pvb265 #imolug 19.06 03.07
19.06.2013 03.07.2013 @pvb265 #imolug bash Syntax
19.06.2013 03.07.2013 @pvb265 #imolug bash Syntaxσύνταξις "arrangement" from σύν syn, "together", and τάξις táxis, "an ordering"
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax comment #à #
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax comment # singole quote ' X ' ' ' '? ' à # any trasformations
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax comment # singole quote ' X ' ' ' '? ' à # any trasformations double quote “ X ”“ 2 any trasformations buts $ ~ ! * @
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax comment # singole quote ' X ' ' ' '? ' à # any trasformations double quote “ X ”“ 2 any trasformations buts $ ~ ! * @ ANSI-C quoting | b backspace f form feed n newline r carriage return t horizontal tab v vertical tab backslash ' single quote " double quote nnn the octal value nnn xHH the hexadecimal value HH
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax variable vector NAME=”test” echo $NAME NAME=(test1 test2 test3) echo $TEST[0]
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ...
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... MacBook-Pro-di-valerio:~ valeriobalbi$ echo "the shell I'm using is $SHELL and his value is in " '$SHELL' the shell I'm using is /bin/bash and his value is in $SHELL
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ export i=2 MacBook-Pro-di-valerio:~ valeriobalbi$ until [ $i -lt 0 ]; do echo $i; export i=$(($i-1)); done 2 1 0
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ export i=2 MacBook-Pro-di-valerio:~ valeriobalbi$ while [ $i -ge 0 ]; do echo $i; export i=$(($i-1)); done 2 1 0
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ while true; do date; sleep 2; done Mar 2 Lug 2013 00:58:07 CEST Mar 2 Lug 2013 00:58:09 CEST Mar 2 Lug 2013 00:58:11 CEST ^C
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ for i in 2 1 0; do echo $i; done 2 1 0
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ for i in $(ls); do echo $i; done . .. file_one file_two
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until test-command; do commands; done while test-command; do commands; done for name in lists; do commands; done for (( exp1; exp2; exp3 )); do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ for (( i=0 ; $i<3; i++ )); do echo $i; done 0 1 2
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until while for command if test-command; then commands; ficonditional if test-command; then commands; else commands; fi if test-command; then commands; elif commands; else commands; fi if test-command; then commands; (elif commands;)* else commands; fi case name in value) commands;; … value) commands;; esac; select name in words; do commands; done
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until while for command if test-command; then commands; ficonditional if test-command; then commands; else commands; fi if test-command; then commands; elif commands; else commands; fi if test-command; then commands; (elif commands;)* else commands; fi case name in (value) commands;; )+ esac commands; select name in words; do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ export i=start; case $i in > start) > echo "start command placeholder";; > stop) > echo "stopping command placeholder";; > esac Start command placeholder
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until while for command if test-command; then commands; ficonditional if test-command; then commands; else commands; fi if test-command; then commands; elif commands; else commands; fi if test-command; then commands; (elif commands;)* else commands; fi case name in (value) commands;; )+ esac commands; select name in words; do commands; done MacBook-Pro-di-valerio:~ valeriobalbi$ export i=”one two”; select j in $i; do echo $j; done 1) one 2) two #? 1 one
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until while for command if case select commandconditional arithmetics logical complex (( expression )) [[ expression ]]
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until while for command if case select commandconditional arithmetics logical complex MacBook-Pro-di-valerio:~ valeriobalbi$ export i=10; ((i--)); echo $i 9 (( expression )) [[ expression ]]
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax command verb parameter1 parameter2 parameter3 ... looping until while for command if case select commandconditional arithmetics logical complex MacBook-Pro-di-valerio:~ valeriobalbi$ if [[ -a /etc/passwd || -b /etc/passwd ]]; then ls -l /etc/passwd; fi -rw-r--r-- 1 root wheel 5148 18 Nov 2011 /etc/passwd MacBook-Pro-di-valerio:~ valeriobalbi$ if [[ -a /etc/passwd && -b /etc/passwd ]]; then ls -l /etc/passwd; fi MacBook-Pro-di-valerio:~ valeriobalbi$ (( expression )) [[ expression ]]
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax parentheses ( list ) curly brace new environment, space needed { list; } same environment, operational token
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax parentheses ( list ) curly brace new environment, space needed { list; } same environment, operational token function name ( ) { commands; } redirections name ( ) { commands; } redirections undef name FUNCNEST != 0 local definition variable
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax parentheses ( list ) curly brace MacBook-Pro-di-valerio:~ valeriobalbi$ foo(){ # do something # if not false call foo foo } MacBook-Pro-di-valerio:~ valeriobalbi$ foo new environment, space needed { list; } same environment, operational token function name ( ) { commands; } redirections name ( ) { commands; } redirections undef name FUNCNEST != 0 local definition variable infinite loop
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax parentheses ( list ) curly brace MacBook-Pro-di-valerio:~ valeriobalbi$ export FUNCNEST=5 MacBook-Pro-di-valerio:~ valeriobalbi$ foo(){ # do something # if not false call foo foo } MacBook-Pro-di-valerio:~ valeriobalbi$ foo MacBook-Pro-di-valerio:~ valeriobalbi$ undef foo MacBook-Pro-di-valerio:~ valeriobalbi$ foo -bash: foo: command not found new environment, space needed { list; } same environment, operational token function name ( ) { commands; } redirections name ( ) { commands; } redirections undef name FUNCNEST != 0 local definition variable
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax parentheses ( list ) curly brace new environment, space needed { list; } same environment, operational token built-in function function definition . filename break n cd .. cd - cd directory eval exec command exit n export pwd readonly name return n shift n test umask mode unset name bash specificsh specific
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax parentheses ( list ) curly brace new environment, space needed { list; } same environment, operational token built-in function function definition . filename break n cd .. cd - cd directory eval exec command exit n export pwd readonly name return n shift n test umask mode unset name alias name=value command name echo help local name=value let printf format values read n source filename ulimit unalias bash specificsh specific
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax positional special
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax positional special useradd -b /home/pvb265 pvb265
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax positional useradd -b /home/pvb265 pvb265 ${0} ${1} ${2} ${3} special
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax positional useradd -b /home/pvb265 pvb265 special $* equivalent ${1}${2}${3}.... $@ equivalent ${1} ${2} ${3} $# parameter number $? return code $$ PID ${0} ${1} ${2} ${3}
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax $CDPATH $HOME $IFS $PATH $PS1 $PS2 bash specificsh specific
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax $CDPATH $HOME $IFS $PATH $PS1 $PS2 $BASH* $ENV $HISTSIZE $HISTFILESIZE LANG SHELL PPID UID GID bash specificsh specific
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax process1
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax process1 stdin
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax process1 stdin stdout stderr
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax process1 stdin stdout stderr 0 1 2
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax cat /etc/hosts > /tmp/output.txt process1
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax cat /etc/hosts > /tmp/output.txt cat /etc/passwd >> /tmp/output.txt process1
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax cat /etc/hosts > /tmp/output.txt cat /etc/passwd >> /tmp/output.txt cat /etc/passwd 2>&1 > /tmp/output.txt process1
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax cat /etc/hosts > /tmp/output.txt cat /etc/passwd >> /tmp/output.txt cat /etc/passwd 2>&1 > /tmp/output.txt > /tmp/output.txt process1
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax process1 process2 pipeline ||
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax Script is a collection of commands #!/bin/sh # RETVAL=0 prog="sssd" # Source function library. . /etc/init.d/functions SSSD=/usr/sbin/sssd LOCK_FILE=/var/lock/subsys/sssd PID_FILE=/var/run/sssd.pid start() { [ -x $SSSD ] || exit 5 echo -n $"Starting $prog: " daemon $SSSD -f -D && success || failure RETVAL=$? echo [ "$RETVAL" = 0 ] && touch $LOCK_FILE return $RETVAL }
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax shabang #! #!/bin/bash
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax shabang #! #!/bin/bash code syntax tree
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax shabang #! #!/bin/bash code syntax tree executable code execution
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax shabang #! #!/bin/bash code syntax tree execution shabang tell O.S. which interpreter use to execute the code For each #! line immagine the fork of a new interpreter
19.06.2013 03.07.2013 @pvb265 #imolug bash Basics Commands Functions Parameters Variables Redirections Scripting Syntax shabang #! #!/bin/bash code syntax tree execution a script file can be executed - bash scriptfilename.sh - scriptfilename.sh
19.06.2013 03.07.2013 @pvb265 #imolug bash Example
19.06.2013 03.07.2013 @pvb265 #imolug bash Example [root@doc ~]# runlevel N 3 [root@doc ~]# cd /etc/rc+TAB+TAB rc rc0.d/ rc1.d/ rc2.d/ rc3.d/ rc4.d/ rc5.d/ rc6.d/ rc.d/ rc.local rc.sysinit [root@doc ~]# cd /etc/rc3.d/ [root@doc rc3.d]# ls -l totale 0 lrwxrwxrwx. 1 root root 15 22 giu 23:52 K01numad -> ../init.d/numad lrwxrwxrwx. 1 root root 16 22 giu 23:57 K01smartd -> ../init.d/smartd lrwxrwxrwx. 1 root root 17 22 giu 21:21 K02oddjobd -> ../init.d/oddjobd lrwxrwxrwx. 1 root root 16 22 giu 23:58 K10psacct -> ../init.d/psacct lrwxrwxrwx. 1 root root 19 22 giu 23:57 K10saslauthd -> ../init.d/saslauthd … lrwxrwxrwx. 1 root root 14 22 giu 23:57 S55sshd -> ../init.d/sshd lrwxrwxrwx. 1 root root 16 23 giu 19:42 S64mysqld -> ../init.d/mysqld lrwxrwxrwx. 1 root root 17 22 giu 21:21 S80postfix -> ../init.d/postfix ... lrwxrwxrwx. 1 root root 11 22 giu 23:48 S99local -> ../rc.local
19.06.2013 03.07.2013 @pvb265 #imolug bash Example [root@doc rc3.d]# cd ../init.d/ [root@doc init.d]# ls -l totale 320 -rwxr-xr-x. 1 root root 1288 23 feb 05:39 abrt-ccpp … -rwxr-xr-x. 1 root root 1698 22 feb 06:38 sandbox -rwxr-xr-x. 1 root root 2056 20 nov 2012 saslauthd -rwxr-xr-x. 1 root root 647 9 gen 12:13 single -rwxr-xr-x. 1 root root 3002 21 feb 23:26 smartd -rwxr-xr-x. 1 root root 4534 22 feb 04:51 sshd -rwxr-xr-x. 1 root root 2647 29 apr 09:50 sssd -rwxr-xr-x. 1 root root 1228 22 giu 2012 sysstat -rwxr-xr-x. 1 root root 2294 22 feb 06:22 udev-post -rwxr-xr-x. 1 root root 1608 22 feb 05:09 winbind -rwxr-xr-x. 1 root root 4799 22 feb 00:23 ypbind [root@doc init.d]# file sshd sshd: Bourne-Again shell script text executable
19.06.2013 03.07.2013 @pvb265 #imolug bash Example #!/bin/bash # # sshd Start up the OpenSSH server daemon # # chkconfig: 2345 55 25 # description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. # # processname: sshd # config: /etc/ssh/ssh_host_key # config: /etc/ssh/ssh_host_key.pub # config: /etc/ssh/ssh_random_seed # config: /etc/ssh/sshd_config # pidfile: /var/run/sshd.pid ### BEGIN INIT INFO # Provides: sshd # Required-Start: $local_fs $network $syslog # Required-Stop: $local_fs $syslog # Should-Start: $syslog # Should-Stop: $network $syslog # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6
19.06.2013 03.07.2013 @pvb265 #imolug bash Example #!/bin/bash # # sshd Start up the OpenSSH server daemon # # chkconfig: 2345 55 25 # description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. # # processname: sshd # config: /etc/ssh/ssh_host_key # config: /etc/ssh/ssh_host_key.pub # config: /etc/ssh/ssh_random_seed # config: /etc/ssh/sshd_config # pidfile: /var/run/sshd.pid ### BEGIN INIT INFO # Provides: sshd # Required-Start: $local_fs $network $syslog # Required-Stop: $local_fs $syslog # Should-Start: $syslog # Should-Stop: $network $syslog # Default-Start: 2 3 4 5 # Default-Stop: 0 1 6
19.06.2013 03.07.2013 @pvb265 #imolug bash Example # Short-Description: Start up the OpenSSH server daemon # Description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. ### END INIT INFO # source function library . /etc/rc.d/init.d/functions # pull in sysconfig settings [ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd RETVAL=0 prog="sshd" lockfile=/var/lock/subsys/$prog # Some functions to make the below more readable KEYGEN=/usr/bin/ssh-keygen SSHD=/usr/sbin/sshd RSA1_KEY=/etc/ssh/ssh_host_key RSA_KEY=/etc/ssh/ssh_host_rsa_key DSA_KEY=/etc/ssh/ssh_host_dsa_key PID_FILE=/var/run/sshd.pid runlevel=$(set -- $(runlevel); eval "echo $$#" )
19.06.2013 03.07.2013 @pvb265 #imolug bash Example # Short-Description: Start up the OpenSSH server daemon # Description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. ### END INIT INFO # source function library . /etc/rc.d/init.d/functions # pull in sysconfig settings [ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd RETVAL=0 prog="sshd" lockfile=/var/lock/subsys/$prog # Some functions to make the below more readable KEYGEN=/usr/bin/ssh-keygen SSHD=/usr/sbin/sshd RSA1_KEY=/etc/ssh/ssh_host_key RSA_KEY=/etc/ssh/ssh_host_rsa_key DSA_KEY=/etc/ssh/ssh_host_dsa_key PID_FILE=/var/run/sshd.pid runlevel=$(set -- $(runlevel); eval "echo $$#" )
19.06.2013 03.07.2013 @pvb265 #imolug bash Example # Short-Description: Start up the OpenSSH server daemon # Description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. ### END INIT INFO # source function library . /etc/rc.d/init.d/functions # pull in sysconfig settings [ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd RETVAL=0 prog="sshd" lockfile=/var/lock/subsys/$prog # Some functions to make the below more readable KEYGEN=/usr/bin/ssh-keygen SSHD=/usr/sbin/sshd RSA1_KEY=/etc/ssh/ssh_host_key RSA_KEY=/etc/ssh/ssh_host_rsa_key DSA_KEY=/etc/ssh/ssh_host_dsa_key PID_FILE=/var/run/sshd.pid runlevel=$(set -- $(runlevel); eval "echo $$#" )
19.06.2013 03.07.2013 @pvb265 #imolug bash Example # Short-Description: Start up the OpenSSH server daemon # Description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. ### END INIT INFO # source function library . /etc/rc.d/init.d/functions # pull in sysconfig settings [ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd RETVAL=0 prog="sshd" lockfile=/var/lock/subsys/$prog # Some functions to make the below more readable KEYGEN=/usr/bin/ssh-keygen SSHD=/usr/sbin/sshd RSA1_KEY=/etc/ssh/ssh_host_key RSA_KEY=/etc/ssh/ssh_host_rsa_key DSA_KEY=/etc/ssh/ssh_host_dsa_key PID_FILE=/var/run/sshd.pid runlevel=$(set -- $(runlevel); eval "echo $$#" )
19.06.2013 03.07.2013 @pvb265 #imolug bash Example # Short-Description: Start up the OpenSSH server daemon # Description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. ### END INIT INFO # source function library . /etc/rc.d/init.d/functions # pull in sysconfig settings [ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd RETVAL=0 prog="sshd" lockfile=/var/lock/subsys/$prog # Some functions to make the below more readable KEYGEN=/usr/bin/ssh-keygen SSHD=/usr/sbin/sshd RSA1_KEY=/etc/ssh/ssh_host_key RSA_KEY=/etc/ssh/ssh_host_rsa_key DSA_KEY=/etc/ssh/ssh_host_dsa_key PID_FILE=/var/run/sshd.pid runlevel=$(set -- $(runlevel); eval "echo $$#" )
19.06.2013 03.07.2013 @pvb265 #imolug bash Example # Short-Description: Start up the OpenSSH server daemon # Description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. ### END INIT INFO # source function library . /etc/rc.d/init.d/functions # pull in sysconfig settings [ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd RETVAL=0 prog="sshd" lockfile=/var/lock/subsys/$prog # Some functions to make the below more readable KEYGEN=/usr/bin/ssh-keygen SSHD=/usr/sbin/sshd RSA1_KEY=/etc/ssh/ssh_host_key RSA_KEY=/etc/ssh/ssh_host_rsa_key DSA_KEY=/etc/ssh/ssh_host_dsa_key PID_FILE=/var/run/sshd.pid runlevel=$(set -- $(runlevel); eval "echo $$#" )
19.06.2013 03.07.2013 @pvb265 #imolug bash Example # Short-Description: Start up the OpenSSH server daemon # Description: SSH is a protocol for secure remote shell access. # This service starts up the OpenSSH server daemon. ### END INIT INFO # source function library . /etc/rc.d/init.d/functions # pull in sysconfig settings [ -f /etc/sysconfig/sshd ] && . /etc/sysconfig/sshd RETVAL=0 prog="sshd" lockfile=/var/lock/subsys/$prog # Some functions to make the below more readable KEYGEN=/usr/bin/ssh-keygen SSHD=/usr/sbin/sshd RSA1_KEY=/etc/ssh/ssh_host_key RSA_KEY=/etc/ssh/ssh_host_rsa_key DSA_KEY=/etc/ssh/ssh_host_dsa_key PID_FILE=/var/run/sshd.pid runlevel=$(set -- $(runlevel); eval "echo $$#" )
19.06.2013 03.07.2013 @pvb265 #imolug bash Example fips_enabled() { if [ -r /proc/sys/crypto/fips_enabled ]; then cat /proc/sys/crypto/fips_enabled else echo 0 fi } do_rsa1_keygen() { if [ ! -s $RSA1_KEY -a `fips_enabled` -eq 0 ]; then echo -n $"Generating SSH1 RSA host key: " rm -f $RSA1_KEY if test ! -f $RSA1_KEY && $KEYGEN -q -t rsa1 -f $RSA1_KEY -C '' -N '' >&/dev/null; then chmod 600 $RSA1_KEY chmod 644 $RSA1_KEY.pub if [ -x /sbin/restorecon ]; then /sbin/restorecon $RSA1_KEY.pub fi success $"RSA1 key generation" echo else failure $"RSA1 key generation" echo exit 1 fi fi }
19.06.2013 03.07.2013 @pvb265 #imolug bash Example fips_enabled() { if [ -r /proc/sys/crypto/fips_enabled ]; then cat /proc/sys/crypto/fips_enabled else echo 0 fi } do_rsa1_keygen() { if [ ! -s $RSA1_KEY -a `fips_enabled` -eq 0 ]; then echo -n $"Generating SSH1 RSA host key: " rm -f $RSA1_KEY if test ! -f $RSA1_KEY && $KEYGEN -q -t rsa1 -f $RSA1_KEY -C '' -N '' >&/dev/null; then chmod 600 $RSA1_KEY chmod 644 $RSA1_KEY.pub if [ -x /sbin/restorecon ]; then /sbin/restorecon $RSA1_KEY.pub fi success $"RSA1 key generation" echo else failure $"RSA1 key generation" echo exit 1 fi fi }
19.06.2013 03.07.2013 @pvb265 #imolug bash Example fips_enabled() { if [ -r /proc/sys/crypto/fips_enabled ]; then cat /proc/sys/crypto/fips_enabled else echo 0 fi } do_rsa1_keygen() { if [ ! -s $RSA1_KEY -a `fips_enabled` -eq 0 ]; then echo -n $"Generating SSH1 RSA host key: " rm -f $RSA1_KEY if test ! -f $RSA1_KEY && $KEYGEN -q -t rsa1 -f $RSA1_KEY -C '' -N '' >&/dev/null; then chmod 600 $RSA1_KEY chmod 644 $RSA1_KEY.pub if [ -x /sbin/restorecon ]; then /sbin/restorecon $RSA1_KEY.pub fi success $"RSA1 key generation" echo else failure $"RSA1 key generation" echo exit 1 fi fi }
19.06.2013 03.07.2013 @pvb265 #imolug bash Example start() { [ -x $SSHD ] || exit 5 [ -f /etc/ssh/sshd_config ] || exit 6 # Create keys if necessary if [ "x${AUTOCREATE_SERVER_KEYS}" != xNO ]; then do_rsa1_keygen do_rsa_keygen do_dsa_keygen fi echo -n $"Starting $prog: " $SSHD $OPTIONS && success || failure RETVAL=$? [ $RETVAL -eq 0 ] && touch $lockfile echo return $RETVAL }
19.06.2013 03.07.2013 @pvb265 #imolug bash Example start() { [ -x $SSHD ] || exit 5 [ -f /etc/ssh/sshd_config ] || exit 6 # Create keys if necessary if [ "x${AUTOCREATE_SERVER_KEYS}" != xNO ]; then do_rsa1_keygen do_rsa_keygen do_dsa_keygen fi echo -n $"Starting $prog: " $SSHD $OPTIONS && success || failure RETVAL=$? [ $RETVAL -eq 0 ] && touch $lockfile echo return $RETVAL }
19.06.2013 03.07.2013 @pvb265 #imolug bash Example start() { [ -x $SSHD ] || exit 5 [ -f /etc/ssh/sshd_config ] || exit 6 # Create keys if necessary if [ "x${AUTOCREATE_SERVER_KEYS}" != xNO ]; then do_rsa1_keygen do_rsa_keygen do_dsa_keygen fi echo -n $"Starting $prog: " $SSHD $OPTIONS && success || failure RETVAL=$? [ $RETVAL -eq 0 ] && touch $lockfile echo return $RETVAL }
19.06.2013 03.07.2013 @pvb265 #imolug bash Example case "$1" in start) rh_status_q && exit 0 start ;; stop) if ! rh_status_q; then rm -f $lockfile exit 0 fi stop ;; *) echo $"Usage: $0 {start|stop|restart|reload|force-reload|condrestart|try-restart|status}" RETVAL=2 esac exit $RETVAL
19.06.2013 03.07.2013 @pvb265 #imolug bash Example case "$1" in start) rh_status_q && exit 0 start ;; stop) if ! rh_status_q; then rm -f $lockfile exit 0 fi stop ;; *) echo $"Usage: $0 {start|stop|restart|reload|force-reload|condrestart|try-restart|status}" RETVAL=2 esac exit $RETVAL
19.06.2013 03.07.2013 @pvb265 #imolug bash Example Questions?

More Related Content

PDF
Bash in theory and in practice - part one
Valerio Balbi
 
PDF
Bash 4
Pieter Colpaert
 
PDF
bash
Gaurav Saxena
 
PDF
C: A Humbling Language
guestaa63aa
 
PPT
Happy porting x86 application to android
Owen Hsu
 
PPTX
Unix shell scripting basics
Manav Prasad
 
ODP
Eat my data
Peng Zuo
 
PDF
Shell scripting
Ashrith Mekala
 
Bash in theory and in practice - part one
Valerio Balbi
 
Bash 4
Pieter Colpaert
 
bash
Gaurav Saxena
 
C: A Humbling Language
guestaa63aa
 
Happy porting x86 application to android
Owen Hsu
 
Unix shell scripting basics
Manav Prasad
 
Eat my data
Peng Zuo
 
Shell scripting
Ashrith Mekala
 

What's hot (19)

PDF
Be pinched by a cRUSTacean to prevent programming errors !
René Ribaud
 
PDF
Bash is not a second zone citizen programming language
René Ribaud
 
PPT
Unix Shell Scripting Basics
Dr.Ravi
 
PDF
Introduction to Bash Scripting, Zyxware Technologies, CSI Students Convention...
Zyxware Technologies
 
PPT
Unix Shell Scripting Basics
Sudharsan S
 
PDF
Containers for sysadmins
Carlos de Alfonso Laguna
 
PPT
Talk Unix Shell Script
Dr.Ravi
 
PPT
Unix And C
Dr.Ravi
 
PDF
Kernel Recipes 2019 - GNU poke, an extensible editor for structured binary data
Anne Nicolas
 
PPTX
Unix shell scripting
Pavan Devarakonda
 
PPT
Talk Unix Shell Script 1
Dr.Ravi
 
ODP
DevChatt 2010 - *nix Cmd Line Kung Foo
brian_dailey
 
PDF
Introduction to shell scripting
Corrado Santoro
 
PPT
Airlover 20030324 1
Dr.Ravi
 
PPT
PHP-FIG: Past, Present and Future
Phil Sturgeon
 
PPT
Unix Basics
Dr.Ravi
 
PPT
On UnQLite
charsbar
 
KEY
Introducing Command Line Applications with Ruby
Nikhil Mungel
 
PPT
01 linux basics
Robson Levi
 
Be pinched by a cRUSTacean to prevent programming errors !
René Ribaud
 
Bash is not a second zone citizen programming language
René Ribaud
 
Unix Shell Scripting Basics
Dr.Ravi
 
Introduction to Bash Scripting, Zyxware Technologies, CSI Students Convention...
Zyxware Technologies
 
Unix Shell Scripting Basics
Sudharsan S
 
Containers for sysadmins
Carlos de Alfonso Laguna
 
Talk Unix Shell Script
Dr.Ravi
 
Unix And C
Dr.Ravi
 
Kernel Recipes 2019 - GNU poke, an extensible editor for structured binary data
Anne Nicolas
 
Unix shell scripting
Pavan Devarakonda
 
Talk Unix Shell Script 1
Dr.Ravi
 
DevChatt 2010 - *nix Cmd Line Kung Foo
brian_dailey
 
Introduction to shell scripting
Corrado Santoro
 
Airlover 20030324 1
Dr.Ravi
 
PHP-FIG: Past, Present and Future
Phil Sturgeon
 
Unix Basics
Dr.Ravi
 
On UnQLite
charsbar
 
Introducing Command Line Applications with Ruby
Nikhil Mungel
 
01 linux basics
Robson Levi
 
Ad

Similar to Bash in theory and in practice - part two (20)

PDF
Becoming a Git Master - Nicola Paolucci
Atlassian
 
PDF
BSDM with BASH: Command Interpolation
Workhorse Computing
 
PPT
ShellAdvanced aaäaaaaaaaaaaaaaaaaaaaaaaaaaaa
ewout2
 
PPT
ShellAdvanced shell scripting programm.ppt
ubaidullah75790
 
PDF
Will iPython replace Bash?
Babel
 
PDF
Will iPython replace bash?
Roberto Polli
 
PDF
Overloading Perl OPs using XS
ℕicolas ℝ.
 
PDF
What is wrong on Test::More? / Test::Moreが抱える問題点とその解決策
kwatch
 
PDF
Gogo shell
jwausle
 
PDF
Performance Profiling in Rust
InfluxData
 
PDF
Hudson以外の何か with 任意
bleis tift
 
DOCX
PrizeExample.DS_Store__MACOSXPrizeExample._.DS_StoreP.docx
ChantellPantoja184
 
PDF
Functional Structures in PHP
Marcello Duarte
 
PDF
Es6 to es5
Shakhzod Tojiyev
 
PPTX
KT on Bash Script.pptx
gogulasivannarayana
 
PPT
Best training-in-mumbai-shell scripting
vibrantuser
 
PDF
Idiomatic Javascript (ES5 to ES2015+)
David Atchley
 
PPTX
PHP 5.3
Chris Stone
 
PDF
Nginx Workshop Aftermath
Denis Zhdanov
 
PPT
Perl Intro 9 Command Line Arguments
Shaun Griffith
 
Becoming a Git Master - Nicola Paolucci
Atlassian
 
BSDM with BASH: Command Interpolation
Workhorse Computing
 
ShellAdvanced aaäaaaaaaaaaaaaaaaaaaaaaaaaaaa
ewout2
 
ShellAdvanced shell scripting programm.ppt
ubaidullah75790
 
Will iPython replace Bash?
Babel
 
Will iPython replace bash?
Roberto Polli
 
Overloading Perl OPs using XS
ℕicolas ℝ.
 
What is wrong on Test::More? / Test::Moreが抱える問題点とその解決策
kwatch
 
Gogo shell
jwausle
 
Performance Profiling in Rust
InfluxData
 
Hudson以外の何か with 任意
bleis tift
 
PrizeExample.DS_Store__MACOSXPrizeExample._.DS_StoreP.docx
ChantellPantoja184
 
Functional Structures in PHP
Marcello Duarte
 
Es6 to es5
Shakhzod Tojiyev
 
KT on Bash Script.pptx
gogulasivannarayana
 
Best training-in-mumbai-shell scripting
vibrantuser
 
Idiomatic Javascript (ES5 to ES2015+)
David Atchley
 
PHP 5.3
Chris Stone
 
Nginx Workshop Aftermath
Denis Zhdanov
 
Perl Intro 9 Command Line Arguments
Shaun Griffith
 
Ad

Recently uploaded (20)

PDF
Review of recent advances in non-invasive hemoglobin estimation
IAESIJAI
 
PPTX
Spectroscopy.pptx food analysis technology
nawahassan45
 
PDF
Mobile App Security Testing_ A Comprehensive Guide.pdf
flufftailshop
 
PDF
Unlocking AI with Model Context Protocol (MCP)
Brian McKeiver
 
PDF
Building Integrated photovoltaic BIPV_UPV.pdf
SandeepSingh286037
 
PDF
KodekX | Application Modernization Development
KodekX
 
PDF
Peak of Data & AI Encore- AI for Metadata and Smarter Workflows
Safe Software
 
PPTX
Programs and apps: productivity, graphics, security and other tools
4mqw9zch22
 
PDF
Reach Out and Touch Someone: Haptics and Empathic Computing
Mark Billinghurst
 
PDF
Machine learning based COVID-19 study performance prediction
IAESIJAI
 
PDF
NewMind AI Weekly Chronicles - August'25 Week I
NewMind AI
 
PDF
Approach and Philosophy of On baking technology
30anthuong17
 
PPTX
Effective Security Operations Center (SOC) A Modern, Strategic, and Threat-In...
ReZa AdineH
 
PDF
MIND Revenue Release Quarter 2 2025 Press Release
MIND CTI
 
PPTX
20250228 LYD VKU AI Blended-Learning.pptx
DatVoNgoc
 
PDF
Empathic Computing: Creating Shared Understanding
Mark Billinghurst
 
PDF
Per capita expenditure prediction using model stacking based on satellite ima...
IAESIJAI
 
PDF
Advanced methodologies resolving dimensionality complications for autism neur...
IAESIJAI
 
PDF
TokAI - TikTok AI Agent : The First AI Application That Analyzes 10,000+ Vira...
SOFTTECHHUB
 
PPTX
Understanding_Digital_Forensics_Presentation.pptx
ImranKhan423233
 
Review of recent advances in non-invasive hemoglobin estimation
IAESIJAI
 
Spectroscopy.pptx food analysis technology
nawahassan45
 
Mobile App Security Testing_ A Comprehensive Guide.pdf
flufftailshop
 
Unlocking AI with Model Context Protocol (MCP)
Brian McKeiver
 
Building Integrated photovoltaic BIPV_UPV.pdf
SandeepSingh286037
 
KodekX | Application Modernization Development
KodekX
 
Peak of Data & AI Encore- AI for Metadata and Smarter Workflows
Safe Software
 
Programs and apps: productivity, graphics, security and other tools
4mqw9zch22
 
Reach Out and Touch Someone: Haptics and Empathic Computing
Mark Billinghurst
 
Machine learning based COVID-19 study performance prediction
IAESIJAI
 
NewMind AI Weekly Chronicles - August'25 Week I
NewMind AI
 
Approach and Philosophy of On baking technology
30anthuong17
 
Effective Security Operations Center (SOC) A Modern, Strategic, and Threat-In...
ReZa AdineH
 
MIND Revenue Release Quarter 2 2025 Press Release
MIND CTI
 
20250228 LYD VKU AI Blended-Learning.pptx
DatVoNgoc
 
Empathic Computing: Creating Shared Understanding
Mark Billinghurst
 
Per capita expenditure prediction using model stacking based on satellite ima...
IAESIJAI
 
Advanced methodologies resolving dimensionality complications for autism neur...
IAESIJAI
 
TokAI - TikTok AI Agent : The First AI Application That Analyzes 10,000+ Vira...
SOFTTECHHUB
 
Understanding_Digital_Forensics_Presentation.pptx
ImranKhan423233
 

Bash in theory and in practice - part two