Redirection

In Unix, there are 3 special files: standard input, standard output and standard error. The first one is a source of input data stream, while the last two are output streams. They are normally your termainl. When you use cat to display a file, the output is sent to the standard output, so that you can see it on the terminal. You are allowed to redirect them to different files:

• Output sent to the standard output:

  cat /etc/sysconfig/network

• Output sent to another file:

  cat /etc/sysconfig/network > /tmp/network

• Standard output redirected to standard error first, but later request redirect standard ouput to another file again:

  cat /etc/sysconfig/network 2>&3 >/tmp/network

• Redirect standard output to standard error and then redirect standard error to another file:

  cat /etc/sysconfig/network 2>&3 3>/tmp/network

  This effectively redirects all standard output and standard error to the file /tmp/network.