Lecture 3 Notes, CSCI 2132.pdf

Lecture 3 Notes, CSCI 2132.pdf - Lecture 3 Notes CSCI 2132...

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3/31/2018 Lecture 3 Notes, CSCI 2132 1/3 Lecture 3, CSCI 2132 Input, Output and Error Channels There are three default I/O channels in a UNIX system: stdin (standard input) stdout (standard output) stderr (standard error) In UNIX, a program reads input from stdin, writes its output to stdout and writes error messages to stderr. By default, all three channels are the terminal running the program or command. Later we will learn how to use a mechanism called redirection to change the default I/O channels of a program. Getting Help Online: man There is a UNIX command called man that can be used to get the manual page about a command or a system function. There are two ways of running man. The syntax of the explicit way is man command-name This can be used to get the manual page of the command "command-name". Some examples are man clear man man You can also specify a keyword and ask man to give a list of programs that fit the keyword, together with a short description of each program. You can then look for the program that performs the task that you would like to perform, and use man in the explicit way to find out how to use the program. The syntax is man -k keyword An example: man -k password Special Characters (Metacharacters) Special characters are characters that are interpreted specially when typed at a UNIX terminal. Here we will learn two of them.
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