Then the system displays an on-line manual about the command. When you reach the end of the manual on the command, execution of the command man is automatically terminated and a prompt character is displayed. Note that this is not a pause and does not save any intermediate results. Specifying Input and Output Most of the commands produce output on the terminal. It is universal in UNIX systems that the terminal can be replaced by a file for either or both of input and output.
Nothing is produced on the terminal.
Note that if there has existed a file named temp, then it is overwritten by the new file and lost. In a similar way, the symbol means to take the input for a command or program from the following file, instead of from the terminal. You can send an email to anyone who has an email address in the network called Internet . Then whatever you type is the email to be sent. When you finish to type the email, type CTRL-d.