How to obtain parameters in the shell?

In the shell, you can obtain parameters through various methods.

1. To access positional parameters, use $ followed by a number. $0 represents the script itself, $1 represents the first argument, $2 represents the second argument, and so on. For example, $0 retrieves the script name and $1 retrieves the first argument.
2. To obtain all parameters, use $@ or $*. $@ represents a list of all parameters, each enclosed in quotation marks. $* represents a string of all parameters, separated by the value of the IFS environment variable.
3. Use $# to get the number of parameters. $# represents the number of parameters passed to the script or function.
4. Use $? to retrieve the exit status of the previous command. A value of 0 for $? indicates that the previous command executed successfully, while a non-zero value indicates failure.
5. Move parameters using the shift command. This command shifts all parameters to the left by one position, moving the value of $2 to $1, the value of $3 to $2, and so on.
6. Use getopts to parse command line options. getopts is a built-in shell command that can be used to parse command line options and parameters.

These techniques can be used in shell scripts to retrieve command line arguments and perform corresponding operations.