Basics

Input/Output Redirection

Three things to remember:

• stdin device is the keyboard

• stdout device is the screen

• stderr is reserved for error output

Output Redirection

$ ls -al > listing will store output of ls -al in a file called listing

>> performs the same function but appends data instead of rewriting a file

Input Redirection

$ sort < listing will push the listing file to the sort command

Pipes

Pipes take the output of one command and feed it into another. You can give any command scrolling output by piping it through less like $ ls -l | less

Error Redirection

When an application has an error, this goes to stderr which can be pushed to a file using 2> so if myscript.sh were to push an error, then $ myscript.sh 2> errors would push only the errors to a file called error. The 2 in the redirect specifies to redirect stderr, with normal output showing on the screen. You can write all output and errors to the same file using something like $ myscript.sh > allout.txt 2>&1