65 lines
2.0 KiB
Scheme
65 lines
2.0 KiB
Scheme
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;;; Copyright (c) 1993 by Olin Shivers.
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;;; Job control code.
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;;; Fork off a process that runs in its own process group. The process
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;;; is (1) placed in its own process group and (2) suspended before
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;;; the process's actual work code is executed, and before FORK-JOB
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;;; returns to the parent. The next time the job is resumed, it will
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;;; begin its actual work.
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(define (fork-job . maybe-thunk)
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(let ((child (fork)))
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(cond (child
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;; PARENT -- wait for child to stop and then set its proc group.
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(let ((status (wait child wait/stopped-children)))
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(if (not (status:stop-sig status)) ; Make sure it didn't die.
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(error "premature job death" status))) ; error call right?
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(set-process-group child child))
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;; CHILD -- suspend until we are put in our own proc group.
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;; The test&suspend isn't atomic; the parent needs to do things
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;; in the right order to make this win.
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(else (let lp ()
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(signal-process 0 signal/stop)
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(if (not (= (pid) (process-group))) (lp)))
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(if (pair? maybe-thunk)
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(call-terminally (car maybe-thunk)))))
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child))
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;;; Foreground a suspended or running background job.
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(define (resume-job proc-group)
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(set-terminal-proc-group 0 proc-group) ; Give tty to job.
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(signal-process-group proc-group signal/cont)
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(let ((status (wait proc-group wait/stopped-children)))
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(set-terminal-proc-group 0 (process-group)) ; Take tty back.
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status))
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;;; What if stdin (fd 0) isn't a tty? Need a (control-tty)
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;;; or (control-tty-fdes) procedure.
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;;; Background a suspended job.
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(define (background-job proc-group)
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(signal-process-group proc-group signal/cont)
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proc-group)
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(define-simple-syntax (run . epf)
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(resume-job (fork-job (lambda () (exec-epf . epf)))))
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(define-simple-syntax (& . epf)
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(background-job (fork-job (lambda () (exec-epf . epf)))))
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;;; Need repl loop that manages some kind of a job table,
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;;; and grabs the terminal back after running a job.
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;;; Should I define a WAIT-JOB procedure?
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;;; Need a (CONTROL-TTY) procedure.
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