Shell command (1)--Variable

Shell variables:

1. System Variables:

• $n: Parameters of the command, n indicates the order of the arguments
• $#: Number of parameters
• $: Program Name
• $?: return value of previous command or function
• $*: Saving parameters as a string
• [Email protected]: Save parameters as an array of characters
• $$: ID number of the current program
• $!: ID number of the previous command

2. Environment variables:

• Path: Command search path.
• Home: The user's home directory
• Histfile: Historical Command file
• Histsize: The maximum number of commands contained in a command history file
• LOGNAME: Current user name
• Shell: The directory where the current shell resides
• Term: terminal type
• Ld_library_path: library file search for Soviet path

To view environment variables, use echo $. For example: Echo $ $TERM

Shell command (1)--Variable