learn shell

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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

[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

...

if [ ]

then

.....

case

case $var_name in

val1)

...

;;

val2)

...

;;

...

;;

esac

for

for var_name in val1 val2 val3 ...

done

while

while [ $i -le 100 ]

...

done

5.Other

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

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