Input and output redirection
Output redirection>
cover
Add
2>error message
2>>error message
&>do not distinguish between right and wrong
&>>do not distinguish between right and wrong
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|The pipe character treats the output data of the previous command as the standard input of the next command.
echo "password" | passwd --stdin
The wildcard
* of the command symbol represents a null value or unlimited
? Single character (not including empty characters)
[0-9 numbers [az] [ 
AZ] letters