Common command statistics for Linux systems and Shell special characters

Shell special characters: 1. Wildcard character 2. Piping

1. Wildcard characters

1.1 asterisk (*): matches any length

1.2 Question mark (? ): Matches a length of characters

1.3 square brackets ([...] ): matches the character specified in it

1.4 Square brackets ([-]): matches a specified range of characters

1.5 square brackets ([^ ...] ): matches except for the characters specified therein

2. Piping |

A pipeline can link multiple commands, such as the output of the first command as input to the second command

2.1WC command

EG:WC Log.txt

Result:2 4 6 Log.txt are a few lines, how many words, how many bytes

Eg:ls/usr/bin | Wc-w Query the number of files in the bin directory

2.2grep command

Eg:grep "lolors"/etc/passwd query lolors account information

3. Input and output redirection

3.1;: Greater than number is new mode

eg:> file_name redirect file_name to the output source for new mode

3.2 >>: for Append mode

3.3 <: input source redirection

Eg:wc<file1 will file1 in the content to do statistics, generally omitted <

3.4 2> or &> directs the error message generated by the command to the specified file

Eg:ls-l Noexist_app 2> Error.txt

2> can only save error messages,&> You can save the correct information and save the error message.

2>> and &>> for Append mode

Common command statistics for Linux systems and Shell special characters