Bash commands

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man {CommandName}

Basics file & folder

cd						change current path
find ./ -name {Filename}			search
touch {FileName}				create filename
mv {FileName} {NewFileName}			move a file or folder
cp {FileName} {NewFileName}			copy a file or folder (-R option for recursive / -V option for verbose)
mkdir -P					create a folder (-P option mean do not warn if already exist)
rm -R {FolderName} 				delete a file or a folder+all subfolder+files (-R option for recursive)
wget http://filetarget.ext			download a file
cat /etc/passwd					dump file content
grep {Text} {FileName}				search Text in FileName
tail -n {Number} {FileName}			get n last lines from FileName (tail -f shows file stream)
head -n {Number} {FileName}			get n first lines from FileName
ls -slash					display folder's content
	-t 					order by date
	-s					display size
	-h					human readable size
	-l					long display
	-a					all content (include files starting with .)
	-d					only folders (ajouter ./*/)
	-r					reverse

Basics : disk

df -h						display hard drive free space
du -km --max-depth=1 | sort -nr			display folder size (need to be in the folder before launch command)
dd if={ImageName}.img of=/dev/sd{DriveId}	apply a disk image to a disk
lsblk						disks details
udevadm info -a -n /dev/sd{b1}			more details for a selected disk
fdisk						partition management tool :

Basics user

su - {UserName}					change current user
sudo 						before a command ex: sudo gedit /etc/network/interfaces
sudo -i						switch to root access
passwd {UserName}				prompt change password
groupadd {group}				add a group
gpasswd -a {user} {group}			create/modify user
useradd {user}					create user
useradd -d /data/{user} {user}			create user with custom home dir
useradd -u {number} {user}			create user with custom ID
useradd -M {user}				create user without home dir
useradd -s /sbin/nologin {user}			create user without login shell
useradd -f 45 {user}				create user with password expire in 45 days
useradd -e AAAA-MM-DD {user}			create user with expire time
useradd -c "{Custom Comment}" {user}		create user with custom comment
userdel {usser} -r  				Remove user (and home dir)
mkhomedir_helper {user}				create user default home dir
usermod {user} -G {group}			add user to group	
chown {User:Group} -R {Folder}			change folder user (-R for recursive)		
chmod 777 -R {Folder}				change folder rights (-R for recursive)
htpasswd -b -m /Usr/passwd {User} {Pass}	change/create user password
pwHash=$( echo -n {pass} | openssl sha1 )	sha1 encode password

Basics misc

echo "{Text}"					write text to output (option -e for \n)
cat "{Text}"					concatenate text to output
set						view en vars
sync						memory flush
/etc/init.d/networking restart			reset network service
ln -s {FolderName} {NewFolderName}		create a symbolic link
rm -f {SymbolicLink}				remove a symbolic link (option -f skip confirmation)
a2enmod {ModuleName}				enable module for apache2
export {VAR}="{Value}"				set env variable
read -p "{text}" {VAR}				prompt text to user and save user typing as VAR
echo "MSG" | mail -s "Subject"	send a mail
c=$a"text"$b					concatenate var + text


space in syntax are important /!\

a=$b						assign value, without space else doesn't works
$((a + b))					addition	
if [ ! $a = $b ]; then				with space and need instruction between "then" and "fi", else doesn't works
{Script to execute}
elif [ ! $a = $c ]; then
{Script to execute}
{Script to execute}
[ $a = $b ] && return 1 || return 0		conditionnal alternative format
if [ $a = $b -o $b = $c ] 			-o mean OR
if [ $a = $b -a $b = $c ] 			-a mean AND
if [ $a = $b -o $b = $c ] || [ $a = $b -a $a = $c ] multiple conditionnal or
if [ $a = $b -o $b = $c ] && [ $a = $b -a $a = $c ] multiple conditionnal and
if [ -z $a ]					is empty or null
if [ ! -z $a ]					not equal to ""
if [ -n $a ]					is not empty or null
if [ $a -eq $b ]				equal
if [ $a -ne $b ]				not equal
if [ $a -gt $b ]				greater than
if [ $a -ge $b ]				greater or equal than
if [ $a -lt $b ]				lower than
if [ $a -le $b ]				lower or equal than
if [ -d $a ]					is a directory	
if [ -e $a ]					file exist	
if [ -f $a ]					is a file
if [ -g $a ]					is group allowed for the file
if [ -r $a ]					is readable	
if [ -s $a ]					file is not 0kb
if [ -u $a ]					is user allowed for file
if [ -w $a ]					is writable
if [ -x $a ]					is executable
if [[ "$a" =~ "$b" ]]				match (reg exp)
if [[ $a == *$b* ]]				match (glob)
if [ "${a/$b}" = $a ]				match (string)
if [ -z "${a##*$b*}" ]				match (string, work with dropbox !)
if [ ${a/$b} = $a ]				match (string)
for file in {Folder}/*				for syntax
{Script to execute}
for i in {$START..$END}				for syntax (another way)
for (( i=0; i<=$END; i++ ))			for syntax (another way)

plus d'infos:

while true; do					while syntax
{Script to execute}

case $1 in					switch case syntax
{Script to execute}
;;						stop matching search
{Script to execute}
;;&						continue matching search		
* )						all case
{Script to execute each time if not break}
cat <<EOF >> {FileName}				write to file all next string with line break include
{StringToWrite}					requier no space between start of line and String


functionName()					create a function
{Script à exécuter}
$1						$1 first param
$2						$2 second param
functionName "Param1" $param2			function call
function fun1()				get function result via echo
echo 34
res=$(fun1)					res = returned string
function fun2()				get function result via return
return "OUTPUT"
if func2;then 					if send a result then it mean 1 else it mean 0
	echo "NO OUTPUT or returned value=FALSE"


tar -cvzf {Archive.tgz} {TargetFolder}		create tar archive
tar -C {TargetFolder} -xvzf {Archive.tgz}	extract tar archive
zip -r {} {TargetFolder}		create zip archive
unzip {} -d {TargetFolder}		extract zip archive
unrar {Archive.rar}				extract rar archive (package unrar-free)
7z x {Archive.ext}				extract any kind of archive (package 7zip-full)

Special commands

$0						script name
${0##*/} = $(echo $0 | rev | cut -d/ -f1 | rev)	allstring after last /
${0%/*} = $(echo $0 | sed "s/\/$Path//g")	all string before last /
${0#*/} 					delete all before first /
${0%/*} 					delete all after last /
${0%%/*} 					delete all after first / 
${1%?}						remove last char
${0:0:1}					first char
${0/a/b}					replace first a by b
${0//a/b}					replace all a by b
${0//@/ }					split char @
${0//[[:alpha:]]/X}				replace alpha by X (can be [[:digit:]])
${0//[a-zA-Z]/X}				and it works with reg exp
${0^^}						to uppercase
${0,,}						to lowercase
${#0} 						string size
${!var}						create a dynamic variable
DATE=`date '+%Y%m%d'`				display date to format AAAAMMJJ
DATE=`date '+%Y/%m/%d %H:%M:%S'`		display date to format AAAA/MM/JJ HH:MM:SS
. {FileName}					include filename in bash scripting
{ScriptToExecute} > /dev/null			stdout
{ScriptToExecute} 2> /dev/null			stderr
{ScriptToExecute} 2>&1 /dev/null		stderr to stdout
{ScriptToExecute} 1>&2 /dev/null		stdout to stderr
{ScriptToExecute} >> /dev/null			add to
{ScriptToExecute} &> /dev/null			stderr and stdout
{ScriptToExecute} >> {ToFile} 2>&1 		stderr to stdout to file
printf '2.4.5a\n2.8b\n2.4.5zz.1\n' | sort -V	sort version list (asc)
$(printf "%03d\n" 7)				padd a number, in this case: 007
$(expr ${a} + ${b}))				force string to be add as integer
echo ${a}| tr -d '\n'				remove line break from a var
((i++))						incremental
& 						at the end of a script call will start it in background
  • string manipulation

  • copy using ssh between 2 server

scp [-12346BCpqrv] [-c cipher] [-F ssh_config] [-i identity_file] [-l limit] [-o ssh_option] [-P port] [-S program][[user@]host1:]file1 ... [[user@]host2:]file2

  • remove ^M (chr(10)chr(13) = windows line break) from a file
sed -i -e "s/\r//g" filename
  • convert string to array
ARR=($0)					basic case (space or : as separator)
ARR=(`echo $0 | tr " " "\n"`)			using tr (\n as separator)
IFS=" " read -ra ARR <<< "$0			using IFS (space as separator)
ARR=(`echo $0 | sed -e 's/ /\n/g'`)		using sed (\n as separator)

to test the array:

for k in "${ARR[@]}";do echo "[$k]";done

array size:

  • copy file to remote computer with ssh
ssh <user>@<ip_du_serveur> -p <port> "echo $(cat ~/.ssh/ >> .ssh/authorized_keys"


grep -R "TEXT" ./				search TEXT in current folder & childs
find ./ -name "filename" -type f -exec grep mytext {} \;

Explications :

find ./						search in current folder
-name "filename"				a file with name matching pattern
-type f						a type file
-exec						execute for each file found
grep mytext {}					search "mytext" in files ( {} replace filename found).
\;						end exec option ( \ can add more commande after)
  • the fastest way:
grep -r -n -i --include="*.htm *.php" "TEXTSTRING" .
"-i" makes it case insensitlve
"./" at the end means you want to start from your current directory, this could be substituted with any directory.
"-r" means do this recursively, right down the directory tree
"-n" prints the line number for matches.
"--include" lets you add file names, extensions. Wildcards accepted




free -m
cat /proc/meminfo


swapoff -a
swapon -a




nc -zv 80

Send a Mail via netcat

echo "HELO" > mail.txt
echo "AUTH LOGIN" >> mail.txt
echo "BASE64encodedEMAIL" >> mail.txt
echo "BASE64encodedPASS" >> mail.txt
echo "MAIL" >> mail.txt
echo "RCPT" >> mail.txt
echo "DATA" >> mail.txt
echo "From:" >> mail.txt
echo "To:" >> mail.txt
echo "Subject: FroggPT BackUP result" >> mail.txt
echo "" >> mail.txt
echo "THIS IS A TEST" >>  mail.txt
echo "" >> mail.txt
echo "." >> mail.txt
echo "QUIT" >> mail.txt
# Send the mail
/usr/bin/nc 25 < mail.txt



echo -n "password" | md5sum			md5 encrypt
echo -n "password" | openssl dgst -sha1		sha1 encrypt
echo "password" | base64			base64 encrypt


echo QWxhZGRpbjpvcGVuIHNlc2FtZQ== | base64 --decode