Operating System Processes

     

(system command) executes a Unix or Windows shell command synchronously (i.e., the call to system does not return until the subprocess has ended), or launches a MacOS application by its creator signature (and returns immediately). The command argument must be a string (of four characters for MacOS). If the command succeeds, the return value is #t, or #f otherwise.

  (system* command argument ...argument ) is like system, but command is a filename that is executed directly (instead of through a shell command or through a MacOS creator signature). Under Unix and Windows, the executed file is passed the specified string arguments; Under MacOS, no arguments can be supplied.

  (execute command) is like system under Unix, but the exeuction of command replaces the MzScheme process. This procedure does not return unless there was an error executing command. If it returns, the result is #<void>. For MacOS, this procedure is system followed by an immediate exit if the target application launches successfully. (Not supported for Windows.)

  (execute* command argument ...argument ) is like execute for Unix, Windows, and MacOS, but command is a filename that is executed directly.

  (process command) executes a shell command asynchronously under Unix. (Not supported for Windows and MacOS.) If the subprocess is launched successfully, the result is a list of four values:

• an input port piped from the subprocess's standard output,
• an output port piped to the subprocess standard input,
• the system process id of the subprocess, and
• an input port piped from the subprocess's standard error.

  (process* command argument ...argument ) is like process for Unix and Windows, but command is a filename that is executed directly. (Not supported for MacOS.)

The  exn:misc:process exception is raised when a low-level error prevents the creation of operating system pipes for process communication.