learn shell

the basic shell skills.

 

• Bourne shell
• • sh
  • ksh
  • Bash
  • psh
  • zsh
• C shell
• • csh
  • tcsh

 

[root@bogon temp]# cat /etc/shells

/bin/sh

/bin/bash

/sbin/nologin

/usr/bin/sh

/usr/bin/bash

/usr/sbin/nologin

/bin/tcsh

/bin/csh

 

 

1.echo

 

[root@bogon temp]# echo "hello world!"

-bash: !": event not found

[root@bogon temp]# echo 'hello world!'

hello world!

 

 

2.sh

 

sh script must declare #!/bin/bash at the begining

you'd better show note 

 

[root@bogon sh]# cat -A hello.sh

#!/bin/bash$

#Ryan$

$

echo "Hello World"$

 

 

cat -A will print all character include \n. You can see, my script hava a $, this is the \n in linux, if in windows, it will be ^M$, you have to run dos2unix to convert it.

 

 

3.Basis

 

 

3.1.history

 

show the history command you had typed

history

!n --execute the num n

!!  --execute the laste , acturelly, we use ↑

 

3.2.alias

 

[root@bogon sh]# alias

alias cp='cp -i'

alias egrep='egrep --color=auto'

alias fgrep='fgrep --color=auto'

alias grep='grep --color=auto'

alias l.='ls -d .* --color=auto'

alias ll='ls -l --color=auto'

alias ls='ls --color=auto'

alias mv='mv -i'

alias rm='rm -i'

alias vi='vim'

alias which='alias | /usr/bin/which --tty-only --read-alias --show-dot --show-tilde'

 

 

3.3 shortcuts

 

ctrl+A     move to line start

ctrl+E     move to line end

ctrl+C     stop

ctrl+L     clean

ctrl+U   delete the command before the cursor

ctrl+K    delete the command after the cursor

ctrl+Y     paste the command that you ctrl+U/K

ctrl+R     search from history

ctrl+D     exit

ctrl+Z     suspend and background

 

 

 

4.command

 

ls -a /etc/ | more

 

grep 

-i ingnore case

-n show linenum

-v negate

 

var

• =bothends can't be space
• $var_name, ${varname}
• `` ==$()

 

envrionment

parent-shell->sub-shell

export var_name=var_value

env

unset var_name

source profile, . ./profile

• /etc/profile
• /etc/profile.d/*.sh
• ~/.bash_profile
• ~/.bashrc
• /etc/bashrc

 

 

 

 

?	one
*	any
[]	the char inside[]
[-]	the char in the range of [-]
[^]	the  opposite char
''	anything is char
""	double quotation, specific char like "$"、"`"、"\"
``	==$()
$()	command to be var
#	note
\	transfferred meaning

 

 

var position

 

$n	$0-command itselt; $1-$9 the attr after command; beyond 10 ${10}
$*	all attrs as a attr
$@	all attrs as attrs
$#	the sum of attrs
$?	the status of the last command : 0? correct:error
$$	current PID
$!	last PID in backgroud

 

 

read -t 30 -p "please input somethind :"  sm

echo $sm

 

 

caculate num

• declare -i cc=$aa+$bb
• dd=$(expr $aa + $bb)
• ff=$(($aa+$bb))

 

 

regular

 

*	behind char any times
.	one char
^	begin
$	end
[]	any inside char
[^]	can be inside char
\	transfer
\{n\}	n times behind. [0-9]\{4\}  ~ 1234; [1][3-8][0-9]\{9\} ~ tel
\{n,\}	at least n times
\{n,m\}	at least n times and at most m times
.*	any char any times
\.$	end with .

 

 

output

 

command >file         cover

command >>file       append

err command 2>file

err command2>>file

 

command>file 2>&1

command  &>> file

 

char cut

 

cut

-d seperator

-f the index

 

[root@00:09:13 /temp/project/sh]$ cut -d ":" -f 1,3 /etc/passwd

root:0

bin:1

 

[root@00:13:16 /temp/project/sh]$ cat /etc/passwd | grep /bin/bash | grep -v root | cut -d ":" -f 1,3

amandabackup:33

ryan:1000

yue:1001

yangmi:1002

bimm:1003

cangls:1004

st:1005

 

 

 

printf

%ns:      n char

%ni:       n num

%m.nf     12.34

 

 

awk

 awk [POSIX or GNU style options] -f progfile [--] file ...

 

 

[root@00:24:15 /temp/project/sh]$ cat stu.txt

name    age aa   

mrf    12    bb

ryan    18    vv

[root@00:24:31 /temp/project/sh]$ awk '{printf $2 "\t" $3 "\n"} ' stu.txt

age    aa

12    bb

18    vv

 

[root@00:24:33 /temp/project/sh]$ df -h | awk '{print $1 "\t" $5 "\t" $6}'

[root@00:29:04 /temp/project/sh]$ df -h

文件系统                 容量  已用  可用 已用% 挂载点

/dev/mapper/centos-root   50G  5.3G   45G   11% /

devtmpfs                 1.6G     0  1.6G    0% /dev

tmpfs                    1.6G     0  1.6G    0% /dev/shm

tmpfs                    1.6G  9.0M  1.6G    1% /run

tmpfs                    1.6G     0  1.6G    0% /sys/fs/cgroup

/dev/mapper/centos-home  278G   37M  278G    1% /home

/dev/sda6                497M  162M  335M   33% /boot

tmpfs                    327M     0  327M    0% /run/user/0

[root@00:29:12 /temp/project/sh]$ df -h | grep root | awk '{print $5}' | cut -d "%" -f111

 

 

 

 

sed

 

change the file line2

sed -i '2c theReplaceMsg'  file

 

p     printf

d     delte

a     append

 i     insert

c     replace   line

s     sed 'ns/old/new/g' file

 

 

if

 

[root@bogon sh]# [ "$aa"=="$bb" ] && echo yes || echo no

yes

 

-n var_name      if var_name!=null return true

-z  var_name      if var_name==null return true

! var_name     opposite  

 

 

if [    ]  ;then

  ....

elif [    ]

     then

     ...

else

     ...

fi

or

if [   ]

     then

.....

fi

 

     

case

 

case $var_name in

     val1)

          ...

          ;;

     val2)

          ...

          ;;

     *)

          ...

          ;;

 esac

 

 

for

 

for var_name in val1 val2 val3 ...

     do

          ..

     done

 

 

while

 

while [  $i -le 100    ]

     do

          ...

     done

 

 

 

 

5.Other

 

ps

 

USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND

root         1  0.0  0.1  41632  4060 ?        Ss   5月13   0:12 /usr/lib/systemd/systemd --switched-root --system --deserialize 21

root         2  0.0  0.0      0     0 ?        S    5月13   0:00 [kthreadd]

root         3  0.0  0.0      0     0 ?        S    5月13   0:05 [ksoftirqd/0]

root         7  0.0  0.0      0     0 ?        S    5月13   0:00 [migration/0]

root         8  0.0  0.0      0     0 ?        S    5月13   0:00 [rcu_bh]

root         9  0.0  0.0      0     0 ?        S    5月13   0:00 [rcuob/0]

root        10  0.0  0.0      0     0 ?        S    5月13   0:00 [rcuob/1]

root        11  0.0  0.0      0     0 ?        S    5月13   0:00 [rcuob/2]

root        12  0.0  0.0      0     0 ?        S    5月13   0:00 [rcuob/3]

root        13  0.0  0.0      0     0 ?        S    5月13   4:18 [rcu_sched]

 

top

 

kill

 

kill -1  restart

kill -9  pid  (force)

kill 15  pid  (default)

 

 

crond

crontab -e