All about Redirection

There are three special file descriptors: stdin, stdout and stderr (std stands for standard), which are defined as file descriptor 0, 1 and 2. You can do different types of redirections with them.

• redirect stdout to a file

ls -la > la.log

• redirect stderr to a file

ack 'pattern' 2> ack-error.log

• redirect stdout to stderr

ack 'pattern' 1>&2

• redirect stderr to stdout

ack 'pattern' 2>&1

• redirect stderr and stdout to a file

ack 'pattern' &> /dev/null

References

1. All about redirection from TLDP
2. Linux file descriptor