- (system STRING) procedure
Execute shell command. The functionality offered by this procedure depends on the capabilities of the host shell. If the forking of a subprocess failed, an exception is raised. Otherwise the return status of the subprocess is returned unaltered.
On a UNIX system, that value is the raw return value of waitpid(2), which contains signal, core dump and exit status. It is 0 on success. To pull out the signal number or exit status portably requires POSIX calls, but in a pinch you can use something like this:
;; Returns two values: #t if the process exited normally or #f otherwise; ;; and either the exit status, or the signal number if terminated via signal. (define (process-status rc) (define (wait-signaled? x) (not (= 0 (bitwise-and x 127)))) (define (wait-signal x) (bitwise-and x 127)) (define (wait-exit-status x) (arithmetic-shift x -8)) (if (wait-signaled? rc) (values #f (wait-signal rc)) (values #t (wait-exit-status rc)))) #;> (process-status (system "exit 42")) #t 42