Caché ObjectScript Reference
$ZF(-2)
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Executes an operating system command or program as a child process, asynchronously. (Deprecated)
Synopsis
$ZF(-2,program)
Parameter
program Optional — The operating system command or program to be executed as a child process, specified as a quoted string. If you omit program, $ZF(-2) launches the operating system shell.
Description
Note:
$ZF(-2) is a deprecated function. It is described here for compatibility with existing code only. All new code development should use $ZF(-100).
$ZF(-2) permits a Caché process to invoke a program or a command of the host operating system. $ZF(-2) executes the operating system command specified in program as a spawned child process from the current console. It executes asynchronously; it returns immediately after spawning the child process and does not wait for the process to terminate. Input and output devices default to the null device.
$ZF(-2) does not return the child process exit status. Instead, if the child process was created successfully,$ZF(-2) returns 0. $ZF(-2) returns -1 if a child process could not be forked.
Because $ZF(-2) does not wait for a response from the spawned child process, you can shut down Caché while the child process is executing.
$ZF(-2) closes the parent process principal device (specified in $PRINCIPAL) before executing the operating system command. This is done because the child process executes concurrently with the parent. If $ZF(-2) did not close $PRINCIPAL, output from the parent and the child would become intermingled. When using $ZF(-2) you should redirect I/O in the command if you wish to recover output from the child process. For example:
   SET x=$ZF(-2,"ls -l > mydir.txt")
$ZF(-2) with no specified parameters launches the default operating system shell. For further details, see Issuing Operating System Commands in Using the Callout Gateway.
If a pathname supplied in program contains a space character, pathname handling is platform-dependent. Windows and UNIX® permit space characters in pathnames, but the entire pathname containing spaces must be enclosed in an additional set of double quote (") characters. This is in accordance with the Windows cmd /c statement. For further details, specify cmd /? at the Windows command prompt.
You can use the NormalizeFilenameWithSpaces() method of the %Library.File class to handle spaces in pathnames as appropriate for the host platform.
$ZF(-2) is a privileged operation, which requires the %System_Callout:U privilege. See Adding the %System_Callout:USE Privilege in Using the Callout Gateway for details.
Auditing
An OS command audit record is added to the audit log for each $ZF(-2) call. This record includes information such as the following:
Execute O/S command Directory: c:\182u5\mgr\ 
Command: ls -lt 4002 - Detached
The Detached keyword indicates the call is $ZF(-2); a $ZF(-1) call does not have this keyword.
$ZF(-2), $ZF(-1), and $ZF(-100)
These three functions are in most respects identical. $ZF(-100) is the preferred function for all purposes, replacing both $ZF(-1) and $ZF(-2).
See Also