Pass the specified command to the operating system.

spawn  OSCommand

Example: spawn "rm -i *.p[0-9][0-9] "


Parameter Data Type Description
OSCommand String Operating system command. The string can be up to 2047 bytes.

Return Values

Values returned in $status
Value Meaning
<0 An operating system error occurred.
0 OSCommand was successfully spawned. $result is set to the value returned by OSCommand.


Allowed in all component types.


The spawn statement clears the screen and passes the OSCommand to the operating system on which the application is running. In a client/server environment, this is the client machine.

You may need to use the refresh statement to repaint the Uniface screen following spawn.

The OSCommand is spawned as an asynchronous process, making it appropriate for interactive applications. To run a synchronous OS command and catch the result, implement an OS service and use activate to call the COMMAND operation on the service.


On Microsoft Windows platforms, you can spawn the command as a synchronous process by prefixing the command with a hash character (#). In the following example, the Uniface application is suspended until the program conv_val ends:

; start conv_val to convert file specified in vFile
spawn "#conv_val.exe %%vFile.raw"
; load processed values into vValues
fileload "%%$1.dat",vValues


Under Unix, a spawned process that detaches itself from the parent process can be used for interprocess communication.

You can spawn the command as a synchronous process using the standard command:

spawn  OSCommand

You can also spawn the command as an asynchronous call by using the ampersand character (&) at the end of the command:

spawn  OSCommand&

Interactively Removing Print Files

The following example uses the spawn statement to interactively remove any print files (those ending in .p00 through .p99). This example uses the Unix rm command, which should be in the user's path (Unix systems only).

trigger detail
spawn "rm -i *.p[0-9][0-9] "
askmess "Press space bar to return."," ",-1

Related Topics