Summary of Linux basics 2 | vim and bash

Learning notes of "bird's private dishes"

1. Use of vim

  • General instruction mode: vim mode
  • Editing mode: press "i, I, o, O, a, A, r, R" in normal mode to enter editing mode
  • Command line command mode: enter ": /?" in general mode Any one, you can move the cursor to the bottom column

vim fileName can create a new file. After editing, press ESC to enter: wq to finish editing and exit. If the file permission is wrong and cannot be written, you can add one! Indicates forced writing, i.e.: wq!, But this can only be established when "your authority can be changed"

In the general command mode: press u to cancel the modification in the editing mode, move 30 lines of cursor down 30 j, and move 30 lines of cursor up 30 k

Rookie tutorial vim

2.BASH

2.1 understanding bash and shell

Communicate the input instructions with the Kernel through the "Shell" so that the Kernel can control the hardware to work correctly

History: history query function

Tab key: automatic completion

Alias: Command alias setting function, such as: alias lm='ls -al ', lm and ls -al functions are the same. To cancel alias setting, unlias lm

[root@VM-20-9-centos /]# 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 which='(alias; declare -f) | /usr/bin/which --tty-only --read-alias --read-functions --show-tilde --show-dot'
alias xzegrep='xzegrep --color=auto'
alias xzfgrep='xzfgrep --color=auto'
alias xzgrep='xzgrep --color=auto'
alias zegrep='zegrep --color=auto'
alias zfgrep='zfgrep --color=auto'
alias zgrep='zgrep --color=auto'

Wildcard: wildcard: for example, check the file or folder starting with x under the / usr/bin folder

[root@VM-20-9-centos /]# ls -l /usr/bin/x*
lrwxrwxrwx  1 root root       7 4 June 24, 2020 /usr/bin/x86_64 -> setarch
-rwxr-xr-x  4 root root 1257912 10 December 2020 /usr/bin/x86_64-redhat-linux-c++
-rwxr-xr-x  4 root root 1257912 10 December 2020 /usr/bin/x86_64-redhat-linux-g++
-rwxr-xr-x  3 root root 1253912 10 December 2020 /usr/bin/x86_64-redhat-linux-gcc
-rwxr-xr-x  3 root root 1253912 10 December 2020 /usr/bin/x86_64-redhat-linux-gcc-8
-rwxr-xr-x. 1 root root     424 5 November 2019 /usr/bin/x86_64-redhat-linux-gnu-pkg-config
-rwxr-xr-x  1 root root   32832 10 June 22, 2020 /usr/bin/x86_energy_perf_policy
-rwxr-xr-x. 1 root root   90312 5 November 2019 /usr/bin/xargs
-rwxr-xr-x  1 root root  340216 11 September 2019 /usr/bin/xgettext
-rwxr-xr-x  1 root root   20656 4 July 2020 /usr/bin/xmlcatalog
-rwxr-xr-x  1 root root   75096 4 July 2020 /usr/bin/xmllint
-rwxr-xr-x. 1 root root   35680 5 November 2019 /usr/bin/xmlwf
-rwxr-xr-x  1 root root   29248 10 May 15, 2020 /usr/bin/xsltproc
-rwxr-xr-x  1 root root   23440 11 December 2019 /usr/bin/xxd
-rwxr-xr-x. 1 root root   91432 5 November 2019 /usr/bin/xz
lrwxrwxrwx. 1 root root       2 5 November 2019 /usr/bin/xzcat -> xz
lrwxrwxrwx. 1 root root       6 5 November 2019 /usr/bin/xzcmp -> xzdiff
-rwxr-xr-x. 1 root root   18376 5 November 2019 /usr/bin/xzdec
-rwxr-xr-x. 1 root root    6632 5 November 2019 /usr/bin/xzdiff
lrwxrwxrwx. 1 root root       6 5 November 2019 /usr/bin/xzegrep -> xzgrep
lrwxrwxrwx. 1 root root       6 5 November 2019 /usr/bin/xzfgrep -> xzgrep
-rwxr-xr-x. 1 root root    5628 5 November 2019 /usr/bin/xzgrep
-rwxr-xr-x. 1 root root    1802 5 November 2019 /usr/bin/xzless
-rwxr-xr-x. 1 root root    2161 5 November 2019 /usr/bin/xzmore

Type: check whether the instruction is a built-in instruction, so type can also be used for purposes similar to the which instruction

[root@VM-20-9-centos /]# type man
man yes /usr/bin/man
[root@VM-20-9-centos /]# type ls
ls yes `ls --color=auto` Alias for
[root@VM-20-9-centos /]# type history
history yes shell Built in
[root@VM-20-9-centos /]# type cd
cd yes shell within

\+ [Enter] key: line feed input

[root@VM-20-9-centos /]# ls \
> -al
 Total dosage 80
dr-xr-xr-x.  19 root root  4096 3 January 10:46 .
dr-xr-xr-x.  19 root root  4096 3 January 10:46 ..
-rw-r--r--    1 root root     0 11 June 26, 2019 .autorelabel
lrwxrwxrwx.   1 root root     7 5 November 2019 bin -> usr/bin
dr-xr-xr-x.   5 root root  4096 4 May 13, 2021 boot
drwxr-xr-x    2 root root  4096 12 October 2019 data
drwxr-xr-x   19 root root  2960 11 July 1:31 dev
drwxr-xr-x. 100 root root 12288 2 June 18-14:25 etc
drwxr-xr-x.   6 root root  4096 2 June 18-14:25 home
lrwxrwxrwx.   1 root root     7 5 November 2019 lib -> usr/lib
lrwxrwxrwx.   1 root root     9 5 November 2019 lib64 -> usr/lib64
drwx------.   2 root root 16384 11 June 26, 2019 lost+found
drwxr-xr-x.   2 root root  4096 5 November 2019 media
drwxr-xr-x.   2 root root  4096 5 November 2019 mnt
drwxr-xr-x.   3 root root  4096 11 June 10:59 opt
dr-xr-xr-x  100 root root     0 11 July 01:31 proc
dr-xr-x---.   6 root root  4096 2 June 28-14:22 root
drwxr-xr-x   31 root root  1020 2 November 23:34 run
lrwxrwxrwx.   1 root root     8 5 November 2019 sbin -> usr/sbin
drwxr-xr-x.   2 root root  4096 5 November 2019 srv
dr-xr-xr-x   13 root root     0 11 July 1:31 sys
drwxrwxrwt.   4 root root  4096 3 January 10:27 tmp
drwxr-xr-x.  12 root root  4096 11 June 26, 2019 usr
drwxr-xr-x.  20 root root  4096 11 June 26, 2019 var

2.2 variables

Definition: variable is to let a specific string represent the content that is not fixed

For example, system variables are generally capitalized PATH, HOME, SHELL and MAIL

Variable access: echo, which is usually preceded by a variable$

[root@VM-20-9-centos /]# echo $PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
[root@VM-20-9-centos /]# echo $HOME
/root
[root@VM-20-9-centos /]# echo $MAIL
/var/spool/mail/root
[root@VM-20-9-centos /]# echo $SHELL
/bin/bash

Setting of variable: =, the beginning of the variable cannot be a number, and the equal sign cannot be followed by a space

[root@VM-20-9-centos /]# echo ${myname}

[root@VM-20-9-centos /]# myname = try setting variables
[root@VM-20-9-centos /]# echo ${myname}
Try the setting change

Unset variable: unset

[root@VM-20-9-centos /]# echo ${myname}
Try setting variables
[root@VM-20-9-centos /]# unset myname
[root@VM-20-9-centos /]# echo ${myname}

environment variable

env: list all environment variables

[root@VM-20-9-centos /]# env
LS_COLORS=rs=0:di=38;5;33:ln=38;5;51:mh=00:pi=40;38;5;11:so=38;5;13:do=38;5;5:bd=48;5;232;38;5;11:cd=48;5;232;38;5;3:or=48;5;232;38;5;9:mi=01;05;37;41:su=48;5;196;38;5;15:sg=48;5;11;38;5;16:ca=48;5;196;38;5;226:tw=48;5;10;38;5;16:ow=48;5;10;38;5;21:st=48;5;21;38;5;15:ex=38;5;40:*.tar=38;5;9:*.tgz=38;5;9:*.arc=38;5;9:*.arj=38;5;9:*.taz=38;5;9:*.lha=38;5;9:*.lz4=38;5;9:*.lzh=38;5;9:*.lzma=38;5;9:*.tlz=38;5;9:*.txz=38;5;9:*.tzo=38;5;9:*.t7z=38;5;9:*.zip=38;5;9:*.z=38;5;9:*.dz=38;5;9:*.gz=38;5;9:*.lrz=38;5;9:*.lz=38;5;9:*.lzo=38;5;9:*.xz=38;5;9:*.zst=38;5;9:*.tzst=38;5;9:*.bz2=38;5;9:*.bz=38;5;9:*.tbz=38;5;9:*.tbz2=38;5;9:*.tz=38;5;9:*.deb=38;5;9:*.rpm=38;5;9:*.jar=38;5;9:*.war=38;5;9:*.ear=38;5;9:*.sar=38;5;9:*.rar=38;5;9:*.alz=38;5;9:*.ace=38;5;9:*.zoo=38;5;9:*.cpio=38;5;9:*.7z=38;5;9:*.rz=38;5;9:*.cab=38;5;9:*.wim=38;5;9:*.swm=38;5;9:*.dwm=38;5;9:*.esd=38;5;9:*.jpg=38;5;13:*.jpeg=38;5;13:*.mjpg=38;5;13:*.mjpeg=38;5;13:*.gif=38;5;13:*.bmp=38;5;13:*.pbm=38;5;13:*.pgm=38;5;13:*.ppm=38;5;13:*.tga=38;5;13:*.xbm=38;5;13:*.xpm=38;5;13:*.tif=38;5;13:*.tiff=38;5;13:*.png=38;5;13:*.svg=38;5;13:*.svgz=38;5;13:*.mng=38;5;13:*.pcx=38;5;13:*.mov=38;5;13:*.mpg=38;5;13:*.mpeg=38;5;13:*.m2v=38;5;13:*.mkv=38;5;13:*.webm=38;5;13:*.ogm=38;5;13:*.mp4=38;5;13:*.m4v=38;5;13:*.mp4v=38;5;13:*.vob=38;5;13:*.qt=38;5;13:*.nuv=38;5;13:*.wmv=38;5;13:*.asf=38;5;13:*.rm=38;5;13:*.rmvb=38;5;13:*.flc=38;5;13:*.avi=38;5;13:*.fli=38;5;13:*.flv=38;5;13:*.gl=38;5;13:*.dl=38;5;13:*.xcf=38;5;13:*.xwd=38;5;13:*.yuv=38;5;13:*.cgm=38;5;13:*.emf=38;5;13:*.ogv=38;5;13:*.ogx=38;5;13:*.aac=38;5;45:*.au=38;5;45:*.flac=38;5;45:*.m4a=38;5;45:*.mid=38;5;45:*.midi=38;5;45:*.mka=38;5;45:*.mp3=38;5;45:*.mpc=38;5;45:*.ogg=38;5;45:*.ra=38;5;45:*.wav=38;5;45:*.oga=38;5;45:*.opus=38;5;45:*.spx=38;5;45:*.xspf=38;5;45:
SSH_CONNECTION=58.251.76.253 52032 10.0.20.9 22
LANG=zh_CN.UTF-8
HISTTIMEFORMAT=%F %T 
HOSTNAME=VM-20-9-centos
OLDPWD=/root
XDG_SESSION_ID=66213
USER=root
PWD=/
HOME=/root
SSH_CLIENT=58.251.76.253 52032 22
SSH_TTY=/dev/pts/0
MAIL=/var/spool/mail/root
TERM=xterm-256color
SHELL=/bin/bash
SHLVL=1
PROMPT_COMMAND=history -a; history -a; printf "\033]0;%s@%s:%s\007" "${USER}" "${HOSTNAME%%.*}" "${PWD/#$HOME/\~}"
LOGNAME=root
DBUS_SESSION_BUS_ADDRESS=unix:path=/run/user/0/bus
XDG_RUNTIME_DIR=/run/user/0
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin
HISTSIZE=3000
LESSOPEN=||/usr/bin/lesspipe.sh %s
_=/usr/bin/env

set: list all variables (including environment variables, user-defined variables and variables related to bash operation interface)

[root@VM-20-9-centos /]# set
BASH=/bin/bash
BASHOPTS=checkwinsize:cmdhist:complete_fullquote:expand_aliases:extglob:extquote:force_fignore:histappend:interactive_comments:login_shell:progcomp:promptvars:sourcepath
BASHRCSOURCED=Y
BASH_ALIASES=()
BASH_ARGC=()
BASH_ARGV=()
BASH_CMDS=()
BASH_COMPLETION_VERSINFO=([0]="2" [1]="7")
BASH_LINENO=()
BASH_REMATCH=()
BASH_SOURCE=()
BASH_VERSINFO=([0]="4" [1]="4" [2]="19" [3]="1" [4]="release" [5]="x86_64-redhat-linux-gnu")
BASH_VERSION='4.4.19(1)-release'
COLUMNS=179
COMP_WORDBREAKS=$' \t\n"\'><=;|&(:'
...

Export: if no variable is followed, all environment variables are displayed as env. If export variable is followed, the current variable can be added to the environment variable, and unset variable can be used to cancel the variable from the environment variable

[root@VM-20-9-centos /]# myname = test the environment variable
[root@VM-20-9-centos /]# export myname
[root@VM-20-9-centos /]# export
declare -x DBUS_SESSION_BUS_ADDRESS="unix:path=/run/user/0/bus"
declare -x HISTSIZE="3000"
declare -x HISTTIMEFORMAT="%F %T "
declare -x HOME="/root"
declare -x HOSTNAME="VM-20-9-centos"
declare -x LANG="zh_CN.UTF-8"
declare -x LESSOPEN="||/usr/bin/lesspipe.sh %s"
declare -x LOGNAME="root"
declare -x LS_COLORS="rs=0:di=38;5;33:ln=38;5;51:mh=00:pi=40;38;5;11:so=38;5;13:do=38;5;5:bd=48;5;232;38;5;11:cd=48;5;232;38;5;3:or=48;5;232;38;5;9:mi=01;05;37;41:su=48;5;196;38;5;15:sg=48;5;11;38;5;16:ca=48;5;196;38;5;226:tw=48;5;10;38;5;16:ow=48;5;10;38;5;21:st=48;5;21;38;5;15:ex=38;5;40:*.tar=38;5;9:*.tgz=38;5;9:*.arc=38;5;9:*.arj=38;5;9:*.taz=38;5;9:*.lha=38;5;9:*.lz4=38;5;9:*.lzh=38;5;9:*.lzma=38;5;9:*.tlz=38;5;9:*.txz=38;5;9:*.tzo=38;5;9:*.t7z=38;5;9:*.zip=38;5;9:*.z=38;5;9:*.dz=38;5;9:*.gz=38;5;9:*.lrz=38;5;9:*.lz=38;5;9:*.lzo=38;5;9:*.xz=38;5;9:*.zst=38;5;9:*.tzst=38;5;9:*.bz2=38;5;9:*.bz=38;5;9:*.tbz=38;5;9:*.tbz2=38;5;9:*.tz=38;5;9:*.deb=38;5;9:*.rpm=38;5;9:*.jar=38;5;9:*.war=38;5;9:*.ear=38;5;9:*.sar=38;5;9:*.rar=38;5;9:*.alz=38;5;9:*.ace=38;5;9:*.zoo=38;5;9:*.cpio=38;5;9:*.7z=38;5;9:*.rz=38;5;9:*.cab=38;5;9:*.wim=38;5;9:*.swm=38;5;9:*.dwm=38;5;9:*.esd=38;5;9:*.jpg=38;5;13:*.jpeg=38;5;13:*.mjpg=38;5;13:*.mjpeg=38;5;13:*.gif=38;5;13:*.bmp=38;5;13:*.pbm=38;5;13:*.pgm=38;5;13:*.ppm=38;5;13:*.tga=38;5;13:*.xbm=38;5;13:*.xpm=38;5;13:*.tif=38;5;13:*.tiff=38;5;13:*.png=38;5;13:*.svg=38;5;13:*.svgz=38;5;13:*.mng=38;5;13:*.pcx=38;5;13:*.mov=38;5;13:*.mpg=38;5;13:*.mpeg=38;5;13:*.m2v=38;5;13:*.mkv=38;5;13:*.webm=38;5;13:*.ogm=38;5;13:*.mp4=38;5;13:*.m4v=38;5;13:*.mp4v=38;5;13:*.vob=38;5;13:*.qt=38;5;13:*.nuv=38;5;13:*.wmv=38;5;13:*.asf=38;5;13:*.rm=38;5;13:*.rmvb=38;5;13:*.flc=38;5;13:*.avi=38;5;13:*.fli=38;5;13:*.flv=38;5;13:*.gl=38;5;13:*.dl=38;5;13:*.xcf=38;5;13:*.xwd=38;5;13:*.yuv=38;5;13:*.cgm=38;5;13:*.emf=38;5;13:*.ogv=38;5;13:*.ogx=38;5;13:*.aac=38;5;45:*.au=38;5;45:*.flac=38;5;45:*.m4a=38;5;45:*.mid=38;5;45:*.midi=38;5;45:*.mka=38;5;45:*.mp3=38;5;45:*.mpc=38;5;45:*.ogg=38;5;45:*.ra=38;5;45:*.wav=38;5;45:*.oga=38;5;45:*.opus=38;5;45:*.spx=38;5;45:*.xspf=38;5;45:"
declare -x MAIL="/var/spool/mail/root"
declare -x OLDPWD="/root"
declare -x PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/root/bin"
declare -x PROMPT_COMMAND="history -a; history -a; printf \"\\033]0;%s@%s:%s\\007\" \"\${USER}\" \"\${HOSTNAME%%.*}\" \"\${PWD/#\$HOME/\\~}\""
declare -x PWD="/"
declare -x SHELL="/bin/bash"
declare -x SHLVL="1"
declare -x SSH_CLIENT="58.251.76.253 52032 22"
declare -x SSH_CONNECTION="58.251.76.253 52032 10.0.20.9 22"
declare -x SSH_TTY="/dev/pts/0"
declare -x TERM="xterm-256color"
declare -x USER="root"
declare -x XDG_RUNTIME_DIR="/run/user/0"
declare -x XDG_SESSION_ID="66213"
declare -x myname="Test the environment variables"

locale: query language family

[root@VM-20-9-centos /]# locale -a
C
C.utf8
en_AG
en_AU
en_AU.utf8
en_BW
en_BW.utf8
en_CA
en_CA.utf8
en_DK
en_DK.utf8
en_GB
en_GB.iso885915
en_GB.utf8
en_HK
en_HK.utf8
en_IE
en_IE@euro
en_IE.utf8
...
[root@VM-20-9-centos /]# locale
LANG=zh_CN.UTF-8
LC_CTYPE="zh_CN.UTF-8"
LC_NUMERIC="zh_CN.UTF-8"
LC_TIME="zh_CN.UTF-8"
LC_COLLATE="zh_CN.UTF-8"
LC_MONETARY="zh_CN.UTF-8"
LC_MESSAGES="zh_CN.UTF-8"
LC_PAPER="zh_CN.UTF-8"
LC_NAME="zh_CN.UTF-8"
LC_ADDRESS="zh_CN.UTF-8"
LC_TELEPHONE="zh_CN.UTF-8"
LC_MEASUREMENT="zh_CN.UTF-8"
LC_IDENTIFICATION="zh_CN.UTF-8"
LC_ALL=
[root@VM-20-9-centos /]# cat etc/locale.conf 
LANG=en_US.UTF-8

Variable keyboard reading, array and declaration

Read: read the input from the keyboard variable

[root@VM-20-9-centos /]# read test  		// Please enter the content after pressing enter
 Hello
[root@VM-20-9-centos /]# echo $test
 Hello

Declare: declare the type of variable

Array: similar to array

[root@VM-20-9-centos /]# var[1]=1
[root@VM-20-9-centos /]# var[2]=2
[root@VM-20-9-centos /]# var[3]=3
[root@VM-20-9-centos /]# echo ${var[1]}, ${var[2]}, ${var[3]}
1, 2, 3

Judgment basis for command execution

cmd1 ; cmd2: multiple instructions can be executed at one time, using; separate

[root@VM-20-9-centos /]# echo aa;echo bb
aa
bb

cmd1 && cmd2,cmd1 || cmd2

[root@VM-20-9-centos /]# echo a && echo b
a
b
[root@VM-20-9-centos /]# echo a || echo b
a

2.3 pipeline command

If a group of data needs to go through several procedures before we can get the format we want, how should we set it? This involves the pipeline command. The pipeline command uses the defining symbol "|"! In addition, pipeline command is different from "continuous command"

The first data after each pipeline must be "instruction"! Moreover, this instruction must be able to accept the data of standard input. Such an instruction can be a "pipeline command". For example, less, more, head, tail, etc. are pipeline commands that can accept standard input. For example, LS, CP and MV are not pipeline commands! Because ls, CP and MV do not accept data from stdin

2.3.1 capture commands cut and grep

Cut: you can cut out a certain section of a piece of information in behavioral units. Cut may be difficult to deal with data connected by multiple spaces

[root@VM-20-9-centos /]# last
root     pts/1        58.251.76.253    Tue Mar  1 13:44   still logged in
root     pts/0        58.251.76.253    Tue Mar  1 10:24 - 14:31  (04:07)
root     pts/0        58.251.76.253    Tue Mar  1 10:17 - 10:24  (00:06)
root     pts/0        58.251.76.253    Mon Feb 28 09:51 - 14:22  (04:31)
root     pts/0        58.251.76.253    Wed Feb 23 16:40 - 17:49  (01:08)
root     pts/1        58.251.76.253    Fri Feb 18 14:00 - 20:10  (06:09)
root     pts/0        58.251.76.253    Fri Feb 18 11:39 - 14:33  (02:54)
lighthou pts/0        81.69.102.16     Wed Feb 16 00:10 - 00:11  (00:01)
lighthou pts/0        81.69.102.25     Wed Feb 16 00:05 - 00:06  (00:01)
lighthou pts/0        81.69.102.18     Wed Feb 16 00:00 - 00:02  (00:02)
lighthou pts/0        81.69.102.22     Tue Feb 15 23:57 - 23:58  (00:01)
...
[root@VM-20-9-centos /]# last | cut -d ' ' -f 1
root
root
root
root
root
root
root
lighthou
lighthou
lighthou
lighthou
...

grep: analyze a line of information. If there is any information we need, take out the line

[root@VM-20-9-centos /]# last | grep 'root' -n
1:root     pts/1        58.251.76.253    Tue Mar  1 13:44   still logged in
2:root     pts/0        58.251.76.253    Tue Mar  1 10:24 - 14:31  (04:07)
3:root     pts/0        58.251.76.253    Tue Mar  1 10:17 - 10:24  (00:06)
4:root     pts/0        58.251.76.253    Mon Feb 28 09:51 - 14:22  (04:31)
5:root     pts/0        58.251.76.253    Wed Feb 23 16:40 - 17:49  (01:08)
6:root     pts/1        58.251.76.253    Fri Feb 18 14:00 - 20:10  (06:09)
7:root     pts/0        58.251.76.253    Fri Feb 18 11:39 - 14:33  (02:54)

2.3.2 sorting commands sort, wc, uniq

Sort: sort

The following default is the first letter beginning with

[root@VM-20-9-centos /]# cat etc/group
root: x:0:
bin: x:1:
daemon: x:2:
sys: x:3:
adm: x:4:
tty: x:5:
disk: x:6:
[root@VM-20-9-centos /]# cat etc/group | sort
adm: x:4:
audio: x:63:
bin: x:1:
cdrom: x:11:
cgred: x:983:
chrony: x:987:

uniq: duplicate data is displayed in only one row

[root@VM-20-9-centos /]# last
root     pts/1        58.251.76.253    Tue Mar  1 13:44   still logged in
root     pts/0        58.251.76.253    Tue Mar  1 10:24 - 14:31  (04:07)
root     pts/0        58.251.76.253    Tue Mar  1 10:17 - 10:24  (00:06)
root     pts/0        58.251.76.253    Mon Feb 28 09:51 - 14:22  (04:31)
root     pts/0        58.251.76.253    Wed Feb 23 16:40 - 17:49  (01:08)
root     pts/1        58.251.76.253    Fri Feb 18 14:00 - 20:10  (06:09)
root     pts/0        58.251.76.253    Fri Feb 18 11:39 - 14:33  (02:54)
lighthou pts/0        81.69.102.16     Wed Feb 16 00:10 - 00:11  (00:01)
lighthou pts/0        81.69.102.25     Wed Feb 16 00:05 - 00:06  (00:01)
lighthou pts/0        81.69.102.18     Wed Feb 16 00:00 - 00:02  (00:02)
lighthou pts/0        81.69.102.22     Tue Feb 15 23:57 - 23:58  (00:01)
...
[root@VM-20-9-centos /]# last | cut -d ' ' -f 1 | sort | uniq -c
      1 
     67 lighthou
      3 reboot
     28 root
      1 wtmp

wc: displays the number of words, lines and characters in a file

[root@VM-20-9-centos /]# cat etc/passwd | wc
     33      70    1719

Among the three numbers output, they respectively represent: "lines, words and characters"

2.3.3 bidirectional redirection tee

A message in the process of data flow processing can be saved and output to the screen for the next instruction to continue processing

[root@VM-20-9-centos ~]# ls
[root@VM-20-9-centos ~]# last | tee last.list
root     pts/1        58.251.76.253    Tue Mar  1 13:44   still logged in
root     pts/0        58.251.76.253    Tue Mar  1 10:24 - 14:31  (04:07)
root     pts/0        58.251.76.253    Tue Mar  1 10:17 - 10:24  (00:06)
root     pts/0        58.251.76.253    Mon Feb 28 09:51 - 14:22  (04:31)
root     pts/0        58.251.76.253    Wed Feb 23 16:40 - 17:49  (01:08)
root     pts/1        58.251.76.253    Fri Feb 18 14:00 - 20:10  (06:09)
root     pts/0        58.251.76.253    Fri Feb 18 11:39 - 14:33  (02:54)
lighthou pts/0        81.69.102.16     Wed Feb 16 00:10 - 00:11  (00:01)
lighthou pts/0        81.69.102.25     Wed Feb 16 00:05 - 00:06  (00:01)
lighthou pts/0        81.69.102.18     Wed Feb 16 00:00 - 00:02  (00:02)
lighthou pts/0        81.69.102.22     Tue Feb 15 23:57 - 23:58  (00:01)
...
[root@VM-20-9-centos ~]# ls
last.list
[root@VM-20-9-centos ~]# cat last.list 
root     pts/1        58.251.76.253    Tue Mar  1 13:44   still logged in
root     pts/0        58.251.76.253    Tue Mar  1 10:24 - 14:31  (04:07)
root     pts/0        58.251.76.253    Tue Mar  1 10:17 - 10:24  (00:06)
root     pts/0        58.251.76.253    Mon Feb 28 09:51 - 14:22  (04:31)
root     pts/0        58.251.76.253    Wed Feb 23 16:40 - 17:49  (01:08)
root     pts/1        58.251.76.253    Fri Feb 18 14:00 - 20:10  (06:09)
root     pts/0        58.251.76.253    Fri Feb 18 11:39 - 14:33  (02:54)
lighthou pts/0        81.69.102.16     Wed Feb 16 00:10 - 00:11  (00:01)
lighthou pts/0        81.69.102.25     Wed Feb 16 00:05 - 00:06  (00:01)
lighthou pts/0        81.69.102.18     Wed Feb 16 00:00 - 00:02  (00:02)
lighthou pts/0        81.69.102.22     Tue Feb 15 23:57 - 23:58  (00:01)
...

2.3.4 character conversion commands tr, join, paste

tr: it can be used to delete the text in a message or replace the text message. It does not change the data in the original file, but only the displayed data

[root@VM-20-9-centos ~]# cat fileTest 
  Line 105:  Expected '!==' and instead saw '!='          eqeqeq
  Line 115:  Expected '!==' and instead saw '!='          eqeqeq
  Line 149:  Expected '===' and instead saw '=='          eqeqeq
  Line 154:  Expected '===' and instead saw '=='          eqeqeq
  Line 155:  Expected '!==' and instead saw '!='          eqeqeq
  Line 166:  Expected '===' and instead saw '=='          eqeqeq
  Line 194:  Expected '===' and instead saw '=='          eqeqeq
  Line 216:  Expected '===' and instead saw '=='          eqeqeq
  Line 262:  Expected '!==' and instead saw '!='
[root@VM-20-9-centos ~]# cat fileTest | tr -d '!'
  Line 105:  Expected '==' and instead saw '='          eqeqeq
  Line 115:  Expected '==' and instead saw '='          eqeqeq
  Line 149:  Expected '===' and instead saw '=='          eqeqeq
  Line 154:  Expected '===' and instead saw '=='          eqeqeq
  Line 155:  Expected '==' and instead saw '='          eqeqeq
  Line 166:  Expected '===' and instead saw '=='          eqeqeq
  Line 194:  Expected '===' and instead saw '=='          eqeqeq
  Line 216:  Expected '===' and instead saw '=='          eqeqeq
  Line 262:  Expected '==' and instead saw '='
[root@VM-20-9-centos ~]# cat fileTest 
  Line 105:  Expected '!==' and instead saw '!='          eqeqeq
  Line 115:  Expected '!==' and instead saw '!='          eqeqeq
  Line 149:  Expected '===' and instead saw '=='          eqeqeq
  Line 154:  Expected '===' and instead saw '=='          eqeqeq
  Line 155:  Expected '!==' and instead saw '!='          eqeqeq
  Line 166:  Expected '===' and instead saw '=='          eqeqeq
  Line 194:  Expected '===' and instead saw '=='          eqeqeq
  Line 216:  Expected '===' and instead saw '=='          eqeqeq
  Line 262:  Expected '!==' and instead saw '!='

Join: the line with "same data" in the two files is added together. The following two files are 4 lines and 9 lines respectively, and both have the same data. There are 36 lines in total after the join

[root@VM-20-9-centos ~]# cat fileTemp | nl
     1	  Line 9:   Expected a default case                     default-case
     2	  Line 20:  Expected a 'break' statement before 'case'  no-fallthrough
     3	  Line 30:  Expected a 'break' statement before 'case'  no-fallthrough
     4	  Line 48:  Expected a default case                     default-case
[root@VM-20-9-centos ~]# cat fileTest | nl
     1	  Line 105:  Expected '!==' and instead saw '!='          eqeqeq
     2	  Line 115:  Expected '!==' and instead saw '!='          eqeqeq
     3	  Line 149:  Expected '===' and instead saw '=='          eqeqeq
     4	  Line 154:  Expected '===' and instead saw '=='          eqeqeq
     5	  Line 155:  Expected '!==' and instead saw '!='          eqeqeq
     6	  Line 166:  Expected '===' and instead saw '=='          eqeqeq
     7	  Line 194:  Expected '===' and instead saw '=='          eqeqeq
     8	  Line 216:  Expected '===' and instead saw '=='          eqeqeq
     9	  Line 262:  Expected '!==' and instead saw '!='
[root@VM-20-9-centos ~]# join fileTemp fileTest | nl
     1	Line 9: Expected a default case default-case 105: Expected '!==' and instead saw '!=' eqeqeq
     2	Line 9: Expected a default case default-case 115: Expected '!==' and instead saw '!=' eqeqeq
     3	Line 9: Expected a default case default-case 149: Expected '===' and instead saw '==' eqeqeq
     4	Line 9: Expected a default case default-case 154: Expected '===' and instead saw '==' eqeqeq
     5	Line 9: Expected a default case default-case 155: Expected '!==' and instead saw '!=' eqeqeq
     6	Line 9: Expected a default case default-case 166: Expected '===' and instead saw '==' eqeqeq
     7	Line 9: Expected a default case default-case 194: Expected '===' and instead saw '==' eqeqeq
     8	Line 9: Expected a default case default-case 216: Expected '===' and instead saw '==' eqeqeq
     9	Line 9: Expected a default case default-case 262: Expected '!==' and instead saw '!='
    10	Line 20: Expected a 'break' statement before 'case' no-fallthrough 105: Expected '!==' and instead saw '!=' eqeqeq
    11	Line 20: Expected a 'break' statement before 'case' no-fallthrough 115: Expected '!==' and instead saw '!=' eqeqeq
    12	Line 20: Expected a 'break' statement before 'case' no-fallthrough 149: Expected '===' and instead saw '==' eqeqeq
    13	Line 20: Expected a 'break' statement before 'case' no-fallthrough 154: Expected '===' and instead saw '==' eqeqeq
    14	Line 20: Expected a 'break' statement before 'case' no-fallthrough 155: Expected '!==' and instead saw '!=' eqeqeq
    15	Line 20: Expected a 'break' statement before 'case' no-fallthrough 166: Expected '===' and instead saw '==' eqeqeq
    16	Line 20: Expected a 'break' statement before 'case' no-fallthrough 194: Expected '===' and instead saw '==' eqeqeq
    17	Line 20: Expected a 'break' statement before 'case' no-fallthrough 216: Expected '===' and instead saw '==' eqeqeq
    18	Line 20: Expected a 'break' statement before 'case' no-fallthrough 262: Expected '!==' and instead saw '!='
    19	Line 30: Expected a 'break' statement before 'case' no-fallthrough 105: Expected '!==' and instead saw '!=' eqeqeq
    20	Line 30: Expected a 'break' statement before 'case' no-fallthrough 115: Expected '!==' and instead saw '!=' eqeqeq
    21	Line 30: Expected a 'break' statement before 'case' no-fallthrough 149: Expected '===' and instead saw '==' eqeqeq
    22	Line 30: Expected a 'break' statement before 'case' no-fallthrough 154: Expected '===' and instead saw '==' eqeqeq
    23	Line 30: Expected a 'break' statement before 'case' no-fallthrough 155: Expected '!==' and instead saw '!=' eqeqeq
    24	Line 30: Expected a 'break' statement before 'case' no-fallthrough 166: Expected '===' and instead saw '==' eqeqeq
    25	Line 30: Expected a 'break' statement before 'case' no-fallthrough 194: Expected '===' and instead saw '==' eqeqeq
    26	Line 30: Expected a 'break' statement before 'case' no-fallthrough 216: Expected '===' and instead saw '==' eqeqeq
    27	Line 30: Expected a 'break' statement before 'case' no-fallthrough 262: Expected '!==' and instead saw '!='
    28	Line 48: Expected a default case default-case 105: Expected '!==' and instead saw '!=' eqeqeq
    29	Line 48: Expected a default case default-case 115: Expected '!==' and instead saw '!=' eqeqeq
    30	Line 48: Expected a default case default-case 149: Expected '===' and instead saw '==' eqeqeq
    31	Line 48: Expected a default case default-case 154: Expected '===' and instead saw '==' eqeqeq
    32	Line 48: Expected a default case default-case 155: Expected '!==' and instead saw '!=' eqeqeq
    33	Line 48: Expected a default case default-case 166: Expected '===' and instead saw '==' eqeqeq
    34	Line 48: Expected a default case default-case 194: Expected '===' and instead saw '==' eqeqeq
    35	Line 48: Expected a default case default-case 216: Expected '===' and instead saw '==' eqeqeq
    36	Line 48: Expected a default case default-case 262: Expected '!==' and instead saw '!='

Paste: paste is much simpler than join. Compared with join, which must compare the data correlation of the two files, paste directly "pastes the two lines together and separates them with the [tab] key"

[root@VM-20-9-centos ~]# paste fileTemp fileTest | nl
     1	  Line 9:   Expected a default case                     default-case	  Line 105:  Expected '!==' and instead saw '!='          eqeqeq
     2	  Line 20:  Expected a 'break' statement before 'case'  no-fallthrough	  Line 115:  Expected '!==' and instead saw '!='          eqeqeq
     3	  Line 30:  Expected a 'break' statement before 'case'  no-fallthrough	  Line 149:  Expected '===' and instead saw '=='          eqeqeq
     4	  Line 48:  Expected a default case                     default-case	  Line 154:  Expected '===' and instead saw '=='          eqeqeq
     5		  Line 155:  Expected '!==' and instead saw '!='          eqeqeq
     6		  Line 166:  Expected '===' and instead saw '=='          eqeqeq
     7		  Line 194:  Expected '===' and instead saw '=='          eqeqeq
     8		  Line 216:  Expected '===' and instead saw '=='          eqeqeq
     9		  Line 262:  Expected '!==' and instead saw '!='

2.3.5 partition command split

split: a large file can be divided into small files according to file size or number of lines

As follows, fileTest is divided into several small files every two lines, with a total of 9 lines. It can be divided into five files, fileSplitaa, fileSplitab, fileSplitac, fileSplitad and fileSplitae

[root@VM-20-9-centos ~]# cat fileTest 
  Line 105:  Expected '!==' and instead saw '!='          eqeqeq
  Line 115:  Expected '!==' and instead saw '!='          eqeqeq
  Line 149:  Expected '===' and instead saw '=='          eqeqeq
  Line 154:  Expected '===' and instead saw '=='          eqeqeq
  Line 155:  Expected '!==' and instead saw '!='          eqeqeq
  Line 166:  Expected '===' and instead saw '=='          eqeqeq
  Line 194:  Expected '===' and instead saw '=='          eqeqeq
  Line 216:  Expected '===' and instead saw '=='          eqeqeq
  Line 262:  Expected '!==' and instead saw '!='
[root@VM-20-9-centos ~]# split -l 2 fileTest fileSplit
[root@VM-20-9-centos ~]# ls
fileSplitaa  fileSplitab  fileSplitac  fileSplitad  fileSplitae  fileTemp  fileTest  last.list
[root@VM-20-9-centos ~]# cat fileSplita*
  Line 105:  Expected '!==' and instead saw '!='          eqeqeq
  Line 115:  Expected '!==' and instead saw '!='          eqeqeq
  Line 149:  Expected '===' and instead saw '=='          eqeqeq
  Line 154:  Expected '===' and instead saw '=='          eqeqeq
  Line 155:  Expected '!==' and instead saw '!='          eqeqeq
  Line 166:  Expected '===' and instead saw '=='          eqeqeq
  Line 194:  Expected '===' and instead saw '=='          eqeqeq
  Line 216:  Expected '===' and instead saw '=='          eqeqeq
  Line 262:  Expected '!==' and instead saw '!='

2.3.6 use of minus sign

Added by wsh on Wed, 02 Mar 2022 08:45:31 +0200

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