The query whether the Bash shell built-in commands:
By type the command: This command can query whether the built-in command
Quick Edit button commands:
Ctrl + u / Ctrl + k: u command to be deleted with the cursor in front of all the commands, command with a cursor k is to remove all instructions behind
shell custom variable function
A simple example, the parameters are targeted to different user's home directory or email directory, so it can reduce a lot of work, each making a similar argument similar commands do not give up.
Use the set of variables: echo, variable setting rules, unset
$ + Able to use a variable representing variable string, the values of variables can be viewed through the variable echo $ (echo $ {variable}).
Can follow the variable name with the number to be assigned to variables = (no spaces equal on both sides, at the beginning of the variable name can not be digitally)
"$ Variable" in double quotation marks can be read variable value
'$ Variable' in single quotation marks can not be read variable value, and becomes a plain string
Use the escape character \ can be Enter, $, \, spaces, 'becomes ordinary characters and other special symbols
Use can export the variable used in other terminals
Variable names are usually capitalized
unset variable name to remove the variable
Command $ (command) is executed first
Environment variable function
Env command can be used to view all the current shell environment variables
Father and son shell: shell parent process that is created first, shell after the child process that is created. The child process will inherit the environment variables, but will not inherit custom variables.