Pipes and Redirection

• The pipe character (|) let's you take the output of one command and have it become the input to another command. For instance:

  ls -lrt | wc -l 

  This runs the ls -lrt command and sends it's output to the wc -l command as input. What will the output be?

• The > character lets you redirect the output of a command from the standard place (i.e. the screen) to a file. For instance:

  ls -lrt > ls.out

  runs the ls -lrt command and saves the output in a file called ls.out.

  If the file exists, it is overwritten. If not, then it creates it.

• The >> character lets you redirect the output of a command and append it to a file. For instance:

  date >> ls.out

  runs the date command and saves the output at the end of a file called ls.out.

  If the file does not exist, it creates it. If not, it adds the output to the end of the file.

• The < character lets you redirect the input to a command so it comes from a file instead of from the keyboard. For instance:

  grep "rwx" < ls.out

• You can use a pipe to get the same result:

  cat ls.out | grep "rwx" 

• Here's the main difference between the pipe and redirection: