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Bash introduction - James Pannacciulli

@ OSCON2014

type cd
info man
man man

Return Status

0
1 to 255
$?
while read var1 var1; do
echo $var1 $var2
done
for name in words; do list; done

for(( expr1 ; expr2: expr3; ))


for (( i=0 ; i<4 ; i++ ))
do
echo $i
done

Select

select name in words; do list; done

Evaluate Expresionss

[ expression] [[ conditional exp ]]
[[ -n  string ]]
[[ -z  string ]]
[[ string != string ]]
[[ string =~ regex ]]
[[ string == string ]]
[[ -e  string ]]
[[ -d  file ]]
[[ -f  file ]]
[[ -t  string ]]
[[ -n  string ]]
[[ -n  string ]]
if [[ 'a' == 'a' ]]
then
    echo "yes"
else
    echo "nope"
fi

CASE

case word in
    pattern1);
        list1:;
    patern2 | pattern3);
        list;;
esac
case one in
    o)
    echo "noooo";;
    o*)
    echo "yeeees";;
    *)
    echo "anything else";;    
esac

Group command

subshell (list) groupcommand { list ; } # trailing ; and space for bash parsing group command lets you run a command in current shell /w same vars groping commands to pipe them

$$ PID of ccurrent shell

echo $(</etc/os-release)

Fedirecting; Command and Process Subst

$(list)
>(list)
<(list)
$*
$@
$-
$$
$!
%?
$_
${12}

Parameter expansion

# extraction
${param:offset}
${param:offset:lenght}
# removal from left
${param#pattern}
${param##pattern}
# removal from right
${param%pattern}
${param%%pattern}

Indexed && associative array

indexed [1] => "potato" associative

arithmetic expansion

(( math stuff ))

name++
++name
--name
name--

echo $(( 3+4 ))
# echo the value of eval

Brace exp

echo {10..55..5}%

Functions

# use function name and params

words ()
{
for word in "$@";
do
    echo "$word";
done
}

Session Portability

$(declare -f xxxxx); xxx

Advanced Bash tut YT

grep -i string filename
# -i for case insensitive

# string manipultaion
man sed
man awk
# cut delimiter filed
cut -d ; -f 4

dot slash is not part of env

./myscipt.sh
sudo cp ./myscript /usr/bin

echo is output to stind

a=Hello
b="Hello world!"
echo $a$b
# declaring int
declare -i d=123
declare -r # read-only
declare -l #loweracse
declare -u #uppercase
# built-in
$BASH_VERSION
$MACHTYPE
$0 # scriptname

Storing the value of the command into a varabile

a=$(ping -c 1 8.8.8.8)
a=$(COMMAND)

arithmetic operaions

d=2
e=$((d+d))
((e++))
echo $e

Comparison operation

[[ EXPRESSION ]]

-gt -lt -eq -le -ge -ne

Logical op

  • [[ $a && $b ]]
  • [[ $a || $b ]]
  • [[ ! $a ]]

[[ -z $a && -n $b ]]

reading files

while read f ; do
    echo $f
done < file.txt

#!/bin/bash

[[ -f ./file.txt ]] && touch file.txt

echo "potato">> file.txt
echo "new stuff" >> file.txt
echo "nowhere to be" >> file.txt
echo "rooomba" >>  file.txt
# test
i=1
while read f ; do
    echo "line $i is: $f"
    ((i++))
done < file.txt

cat file.txt
exit 0

here doc

cat << EndOfTxt
potaoto
motato
roomba
EndOfTxt
# - dash erase leading tabs
cat <<- END
    tomato
END
#!/bin/bash

greentxt="\033[32m"
bold="\033[1m"
normal="\033[0m"
logdate=$(date +"%Y%m%d")
logfile="$logdate"_report.log

echo -e $bold"Quick sys report for: "$greentxt"$HOSTNAME"$normal
printf "\tSystemType:\t%s\n" $MACHTYPE

cat <<- EOF > $logfile
    Report was successfully created!
    Check the report!
EOF

printf "BASH:\t%s\n" $BASH_VERSION >> $logfile

title: - Awesome Bash Commands

Tar

tar -cvf file1.tar file2.txt	# compress a file
tar -xvf file1.tar						# extract a file

Netcat

netcat -k -l 9999 >> example_log.txt		# listening server
date | nc 192.168.0.4 9999							# send output of command
nc localhost 4444 < /bin/bash						#

Nmap

nmap -sP		# ping
nmap -sT		# 3-way handshake
nmap -sV		# system version
sudo nmap -O 

# nmap scripts
# agressive / non agressive scripts
nmap -sC 192.168.0.22
nmap --script "http-*" 192.168.0.34
nmap --script "(ssh and not brute)"
nmap -A			# not recommanded, agressive
xz -d someting.img.xz
dd if=smthin.img of=/dev/s bs=4MB status=progress

title: - Awesome Bash Commands

Tar

tar -cvf file1.tar file2.txt	# compress a file
tar -xvf file1.tar						# extract a file

Netcat

netcat -k -l 9999 >> example_log.txt		# listening server
date | nc 192.168.0.4 9999							# send output of command
nc localhost 4444 < /bin/bash						#

Nmap

nmap -sP		# ping
nmap -sT		# 3-way handshake
nmap -sV		# system version
sudo nmap -O 

# nmap scripts
# agressive / non agressive scripts
nmap -sC 192.168.0.22
nmap --script "http-*" 192.168.0.34
nmap --script "(ssh and not brute)"
nmap -A			# not recommanded, agressive
xz -d someting.img.xz
dd if=smthin.img of=/dev/s bs=4MB status=progress

title: - Awesome Bash Commands

Tar

tar -cvf file1.tar file2.txt	# compress a file
tar -xvf file1.tar						# extract a file

Netcat

netcat -k -l 9999 >> example_log.txt		# listening server
date | nc 192.168.0.4 9999							# send output of command
nc localhost 4444 < /bin/bash						#

Nmap

nmap -sP		# ping
nmap -sT		# 3-way handshake
nmap -sV		# system version
sudo nmap -O 

# nmap scripts
# agressive / non agressive scripts
nmap -sC 192.168.0.22
nmap --script "http-*" 192.168.0.34
nmap --script "(ssh and not brute)"
nmap -A			# not recommanded, agressive
xz -d someting.img.xz
dd if=smthin.img of=/dev/s bs=4MB status=progress