Korn Shell: Unix and Linux Programming Manual, Third Edition, The

Input/Output

Before a command is executed, its input and output may be redirected using a special notation interpreted by the shell. The following may appear anywhere in a simple-command or may precede or follow a command and are not passed on to the invoked command. Command substitution, parameter expansion, and arithmetic substitution occur before word or digit is used except as noted below. File name generation occurs only if the shell is interactive and the pattern matches a single file. Field splitting is not performed.

In each of the following redirections, if file is of the form /dev/tcp/host/port, or /dev/udp/host/port, where host is a hostname or host address, and port is an integer port number, then the redirection attempts to make ...