1. Practice command history, alias special character usage in shell
1.1 Display history commands
Syntax format: history[opyion][arg...]
①If there is no parameter, the history command list will be displayed
②If a positive integer m is given later, the last m lines are displayed
③ If a file name a1 is given later, then a1 is used as the historical file name
1.2 Define aliases
Syntax format: alias[name[value]]...
1.3 shell special characters
1.3.1 Quotes
There are three types of quotation marks: single quotation marks, double quotation marks and back quotation marks
① The characters in the backticks will be treated as shell commands and will be replaced.
② The characters in the single quotation marks will be treated as ordinary characters
. (!) are treated as ordinary characters
1.3.2 Input/Output Redirector
Input redirection:
Output redirection:
2. Shell command application practice
2.1 Briefly describe the purpose of the following documents
① /etc/passwd: user account information
② /etc/shadow: secure user account information
③ /etc/group: group account information
④ /etc/gshadow: Security group account information