The scripting language that Shell interprets and executes can directly call all commands of Linux.
echo output command
-e: supports backslash-controlled character conversion
eg1:echo -e 'ab\bc'
delete left character
eg2:echo -e 'a\tb\tc\nd\te\tf'
Tab and newline output
eg3:echo $PATH
View the environment variables under linux
history command
Syntax: history [options] [history command save file]
Options
-c clear history command
-w Write the history commands in the cache to the history command save file
~/.bash_history default save address
By default, 1000 historical commands are saved, which can be modified in the environment configuration file /etc/profile.
History command calls
a, use the up and down arrows to recall previous history commands
b, use "!n" to repeatedly execute the nth history command
c, use "!!" to repeat the previous command
d, use "! string" to repeat the command at the beginning of the string
Command and file completion
Pressing the "Tab" key will automatically complete it.
alias alias command
Syntax: alias alias='original command'
View a list of aliases: alias
vi ~/.bashrc makes aliases permanent
Remove aliases: unalias aliases
Common shortcut keys in Linux
The blue ones are commonly used and need to be skilled.
Note: Letters are not big or small
I/O redirection
output redirection
> output console information to the specified file
>>
eg1:df -h > log.txt #correct output redirection, overwrite
eg2:lst 2>> error.txt #Error output redirection, append
eg3: ls &> log.txt #correct or error output redirection, overwrite
eg3: lst &>> log.txt #correct or incorrect output redirection, append
input redirection
< takes a file as input to the command.
eg1:wc -l < log.txt #Enter the contents of log.txt to the command before <.
eg2:wall <vi.txt send vi.txt message to everyone via redirection
<<
Take the command between two symbols as input
eg: wc << hello
aaa
bbb
ccc
hello
Note: The symbol (hello) in the last line will end when the symbol (hello) after the first group of "<<" is the same, and only the content between them will be recognized.
multiple commands
; 、&& 、||
eg:lst ; date ; cd /usr/local
eg:lst && date
eg:lst || date
Pipe character: |
Syntax: command1 | command2
Correct output of command 1 as the action object of command 2
Eg: netstat -an | grep 'ESTABLISHED'
netstat network connection command
Syntax: netstat [options]
eg1:netstat -an | grep 'ESTABLISHED' to see how many connections the current computer has
eg2:netstat -antp | grep nginx To view the program whose program name contains "nginx" in the current computer connection, the occupied port, occupied process number, and program name will be displayed.
grep searches files for matching strings
Syntax: grep [options] "search content"
Options
-i ignore case
-n output line number
-v reverse lookup
--color=auto Display the searched keywords in color.
eg: grep -n --color=auto "port" repl1.conf Search for the color keyword in the repl1.conf file, and display the line number and display it in color
wildcard
Eg:
Prepare the data to create the following files
touch abc
touch abcd
touch 0abc
touch 5abc
touch aabc
touch fabc
touch 123
ls ?abc
ls *abc
ls *abc*
ls [abcdefg]abc
ls [0-9]abc
ls [^0-9]abc
other special symbols
Eg:
name=sc
echo '$name'
echo "$name"
echo "\$name"
abc=`data`
echo $abc
abc=$(date)
echo $abc