(ypsilon process) — Posix process interface

(process <name> <args> ...)   procedure

• Runs a child process and returns pid and new textual ports stdin, stdout, stderr opened for the child process.
  
  

  (import (rnrs) (ypsilon process) (only (core) format))
  (call-with-values
    (lambda ()
      (process "grep" "-oE" "([a-z]+)" "-"))
    (lambda (pid stdin stdout stderr)
      (write "1234 hoge 5678" stdin)
      (close-port stdin)
      (format #t "stdout: ~a" (get-string-all stdout))
      (format #t "stderr: ~a~%" (get-string-all stderr))
      (format #t "exit:~a~%" (process-wait pid #f))))
  ; stdout: hoge
  ; stderr: #<eof>
  ; exit:0
  

(process-wait <pid> <nohang>)   procedure

• Waits for the child process specified by <pid> to terminate, then returns its exit status.
• Returns #f immediately if <nohang> is #t and the child process has not terminated.

(process-spawn <search> <env> <stdin> <stdout> <stderr> <name> <args> ...)   procedure

• Runs a child process and returns pid and new binary ports stdin, stdout, stderr if the port is not specified in <stdin> <stdout> <stderr>.
• If <search> is #t, <name> is treated as a filename and the process image is searched using the environment variable PATH. Otherwise name is treated as a pathname.
• <env> is an association list of child process environment.
• <stdin> <stdout> <stderr> can be either #f, port, or socket — specifying #f creates and assigns a new binary port.
  
  

  (import (rnrs) (ypsilon process) (only (core) format destructuring-bind))
  (system "echo '1234 hoge 5678' > /tmp/temp-ypsilon-input")
  (system "rm /tmp/temp-ypsilon-output")
  (call-with-input-file
    "/tmp/temp-ypsilon-input"
    (lambda (in)
      (call-with-output-file
        "/tmp/temp-ypsilon-output"
        (lambda (out)
          (destructuring-bind (pid _ _ stderr)
              (process-spawn #t #f in out #f "grep" "-oE" "([a-z]+)" "-")
            (format #t "exit:~a~%" (process-wait pid #f))
            (system "cat /tmp/temp-ypsilon-output")
            (format #t "stderr: ~a~%" (get-string-all (transcoded-port stderr (native-transcoder)))))))))
  ; exit:0
  ; hoge
  ; stderr: #<eof>
  

(process-shell-command <command>)   procedure

• Runs <command> in the shell.
• Returns pid and ports stdin, stdout, stderr opened for the shell process.
  
  

  (import (rnrs) (ypsilon process) (only (core) format))
  (call-with-values
    (lambda ()
      (process-shell-command "pwd"))
    (lambda (pid stdin stdout stderr)
      (format #t "stdout: ~a" (get-string-all stdout))
      (format #t "exit:~a~%" (process-wait pid #f))))
  ; stdout: /home/digamma/github/ypsilon
  ; exit:0
  

(system <command>)   procedure

• Runs <command> in the shell.
• Returns an exit status after <command> is complete.
  
  

  (import (rnrs) (ypsilon process))
  (system "uname -svr") ;=> 0
  ; Linux 5.13.0-30-generic #33-Ubuntu SMP Fri Feb 4 17:05:14 UTC 2022