Once you have accessed the POSIX subsystem, the POSIX shell is started.
If you are using the POSIX shell interactively, the POSIX shell outputs the value of the PS1 environment variable as a prompt before it reads a command. For a privileged user this is normally either a dollar sign ($) or a hash sign (#) followed by a space character(' ').
Command input has the following format:
Command[ options][ parameter] ...
For command, you must enter the name of a POSIX command or a shell script to be executed. For options, enter control statements to execute commands. For parameter, you must enter a call argument, which the POSIX shell transfers to command. You can also specify several call arguments, independently of the command.
If you are working on a character terminal, command names and call arguments must be separated either by tabulator characters or by spaces. The last call argument, and thus also command input, must be terminated by pressing the enter key, or EM DUE in the case of a block terminal.
You cannot start pure BS2000 programs from within the POSIX shell.
If the screen line for input is too short, you have two options:
Continue writing to the end of the line without pressing the enter key. When the command is completely entered, terminate it by pressing the enter key.
Continue the line with backslash and the enter key. The backslash character (\) counteracts the command termination function of the enter key. You can then continue entereing the command. When the enter key is pressed without backslash (\), the command is executed.
Every POSIX command returns a value to the POSIX shell in which it was invoked, namely its exit status. An error-free procedure returns a value of 0, an errored procedure a value other than 0.
If, when working with a character terminal, a command outputs information on the screen which is larger than the size of a screen page, you can stop the output by pressing the keys CTRL + S and then continue by pressing the keys CTRL + Q. Block terminals do not support this function.
For more detailed information on command input, please refer to the "POSIX Commands" [1] manual.