1. Special symbols
'' What you see is what you get
"" Special symbols will be parsed and run
`` == $() Run the command inside first and leave the result
>
>> Append redirection Append file's last
2> Error redirection Only the wrong information will enter the file through this vulnerability
2>> Error appending redirection
~ The current user's home directory
! Find and run historical commands
!awk The command containing awk The most recent run
history |grep awk
# Comments
The root user's command prompt
$ Take out the contents of the variable
awk $ Take the content of a certain column
Command prompt for ordinary users
* Everything
\ Crowbar Escape Character
&& The previous command is executed successfully and then the next command is executed
ifdown eth0 && ifup eth0|| If the previous command fails to support it, then execute the following command
2. Wildcard
Wildcards are used to find files.
2.1. All, any*
2.2.{} Generate sequence
3. Regular expressions
3.1.What is regularity? Why use it?
The text content is represented by symbols.
Improve efficiency and save trouble.
3.2. Things to note when using regular
Regular expressions are processed by rows
Chinese symbols are prohibited
Configure alias for grep and egrep
cat >>/etc/profile<<EOF
alias grep='grep --color=auto'
alias egrep='egrep --color=auto'
EOF
source /etc/profile
3.3. The difference between regular expressions and wildcards
Purpose
Wildcards---used to match the search file name *.txt *.log Files ending in .txt .log Most commands can be used
Regular ------Match the search content in the file. Lines containing abc.
3.4. Regular Expression Classification
Basic Regularity ^ $ . * [] [^] basic regular expression BRE grep �
Extended Regularity | + {} () ? extended regular expression ERE grep -E/egrep sed -r awk
3.5. Regular expression summary
Continuous occurrence (repeat)
* >=0
+ >=1
? 0 1
{n,m} >=n <=m
{n} ==n
other
Any character
[abc] A whole is equivalent to a character
[a-z] [0-9] [A-Z]
[^abc] Exclude
|
() Backward reference Backward reference Protect first and then use
^
$
.* all
^$
3.6. The difference between basic and extended regularities
grep egrep === grep -E
sed sed -r
awk awk
This is the article about the introduction of regular expressions and wildcards and differences. For more related regular expressions, please search for my previous articles or continue browsing the related articles below. I hope you will support me in the future!