screen

Graphics and Screen4.0 (8.x)Screen Graphics Subsystem Developer's GuideAPIProgrammingUtilities

Start Screen services

Syntax:

        screen [-a]
               [-c filename]
               [-u user_info]
    

Runs on:

QNX OS

Options:

-a
Run screen in headless mode. This option allows screen to only run virtual displays, bypassing any physical displays.
-c filename

Specify filename as the absolute pathname to the configuration file that screen will use. For example:

$ screen -c /usr/lib/graphics/platform/graphics.conf
                

where platform is the name of your target's platform (e.g., imx6x).

Note:

You must specify this -c option. Otherwise, screen won't run.

On your target, all libraries that you specify in the khronos section of your configuration file should reside in the same directory as the configuration file itself.

-u user_info
Switch to the specified user after initialization where user_info can take one of the following forms:
uid:gid,sgid1,sgid2,sgid3,...
All IDs must be numbers. The UID and GID are separated by a colon. The GID can be followed by a comma-separated list of supplementary group IDs. GID and supplementary GIDs are optional.
username,sgid1,sgid2,sgid3,...
The username must be a valid username defined in /etc/passwd; otherwise, the function errors out with EINVAL. The supplementary GIDs are optional and must be a comma-separated list of numbers. The GID is looked up in /etc/passwd. The supplementary GIDs returned are a union of supplementary GIDs (located in /etc/group for the given username) and the GIDs parsed from user_info.

screen does not drop its root privilege until the drop_privileges string is written to /dev/screen/command. This option sets the user that Screen will switch to after root privileges are dropped. Running the drop_privileges command completes screen's initialization, all required modules are loaded and screen transitions to running as the specified user. Running as a general user provides a more secure runtime environment. If there are any unpredictable applications on the system, they won't be able to leverage screen to run undesirable code as a privileged user.

Description:

Run the screen binary from command line to start Screen services. To run screen on your target, run screen from a shell.

Examples:

To start screen:
screen -c /usr/lib/graphics/<platform>/graphics.conf
To start screen as root but switch to user joe when the drop_privileges command is executed:
screen -c /usr/lib/graphics/<platform>/graphics.conf -u joe
User joe needs to be a valid username or screen will fail.
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