Ubuntu Unleashed 2013 Edition: Covering 12.10 and 13.04, Eighth Edition

Redirecting Input and Output

You can create, overwrite, and append data to files at the command line, using a process called input and output redirection. The shell recognizes several special characters for this process, such as >, <, or >>.

In this example, the output of the ls command is redirected to create a file named textfiles.listing:

matthew@seymour:~$ ls *.txt >textfiles.listing

Use output redirection with care because it is possible to overwrite existing files. For example, specifying a different directory but using the same output filename overwrites the existing textfiles.listing:

matthew@seymour:~$ ls /usr/share/doc/mutt-1.4/*.txt >textfiles.listing

Fortunately, most shells are smart enough to recognize when you might do something ...