Linux and Unix Shell Programming

5.7. File redirection

When issuing commands, you can specify where you want the standard input, output and errors to go, and to be able to do this you need to do a bit of redirection. A combination of the most useful redirections with corresponding file descriptors is shown in Table 5.1.

When using standard error in redirection, you must use a file descriptor, but for standard input and output this is optional. Table 5.1 shows both methods for completeness.

Table 5.1. Common file redirection commands

Command > filename	Send standard output to a new filename
Command >> filename	Send standard output to filename (appended)
Command 1 > filename	Send standard output to filename
Command > filename 2>&1	Send all output (including errors) to filename ...