Several small topics of shell variables

1. Describe the results of the following commands

More/etc/shells

Displays all the contents of the shells text.

Echo $SHELL

View the shell program used by the current user.

History-c

Clear historical and practical commands.

Echo $HISTIZE

Record the history of the command bar, the default 1000 bar.

free-m | Head 2

View the current system's memory mem: and swap memory swap size, and display the first two lines.

Read-p "Input Number:" Number

Set input number: variable value.

Expr 2 + 3

2 plus 3 of the total value.

Expr 5% 2

5 divided by 2 to take the remainder.

Expr $USER

View the currently logged on user

Expr $HOME

View Current User Directory

2. Fill in the result values of the following variables.

./exam 2 3 4 5

Perform exam 2 3 4 5 results.

$#

The number of positional parameters in the command line.

$*

The contents of all positional parameters.

$?

The result of the previous command execution, 0 indicates normal, the other numbers are not abnormal.

$o

The process/program name of course execution.

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Several small topics of shell variables