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package lib
import (
"fmt"
"os"
"github.com/johnkerl/miller/v6/pkg/platform"
)
// OpenOutboundHalfPipe returns a handle to a process. Writing to that handle
// writes to the process' stdin. The process' stdout and stderr are the current
// process' stdout and stderr.
//
// This is for pipe-output-redirection in the Miller put/filter DSL.
//
// Note I am not using os.exec.Cmd which is billed as being simpler than using
// os.StartProcess. It may indeed be simpler when you want to handle the
// subprocess' stdin/stdout/stderr all three within the parent process. Here I
// found it much easier to use os.StartProcess to let the stdout/stderr run
// free.
func OpenOutboundHalfPipe(commandString string) (*os.File, error) {
readPipe, writePipe, err := os.Pipe()
if err != nil {
return nil, err
}
var procAttr os.ProcAttr
procAttr.Files = []*os.File{
readPipe,
os.Stdout,
os.Stderr,
}
// /bin/sh -c "..." or cmd /c "..."
shellRunArray := platform.GetShellRunArray(commandString)
process, err := os.StartProcess(shellRunArray[0], shellRunArray, &procAttr)
if err != nil {
return nil, err
}
go process.Wait()
return writePipe, nil
}
// OpenInboundHalfPipe returns a handle to a process. Reading from that handle
// reads from the process' stdout. The process' stdin and stderr are the
// current process' stdin and stderr.
//
// This is for the Miller prepipe feature.
//
// Note I am not using os.exec.Cmd which is billed as being simpler than using
// os.StartProcess. It may indeed be simpler when you want to handle the
// subprocess' stdin/stdout/stderr all three within the parent process. Here I
// found it much easier to use os.StartProcess to let the stdin/stderr run
// free.
func OpenInboundHalfPipe(commandString string) (*os.File, error) {
readPipe, writePipe, err := os.Pipe()
if err != nil {
return nil, err
}
var procAttr os.ProcAttr
procAttr.Files = []*os.File{
os.Stdin,
writePipe,
os.Stderr,
}
// /bin/sh -c "..." or cmd /c "..."
shellRunArray := platform.GetShellRunArray(commandString)
process, err := os.StartProcess(shellRunArray[0], shellRunArray, &procAttr)
if err != nil {
return nil, err
}
// TODO comment somewhere
// https://stackoverflow.com/questions/47486128/why-does-io-pipe-continue-to-block-even-when-eof-is-reached
// TODO comment
go func(process *os.Process, readPipe *os.File) {
_, err := process.Wait()
if err != nil {
fmt.Fprintf(os.Stderr, "%s: %v\n", "mlr", err)
}
readPipe.Close()
}(process, readPipe)
return readPipe, nil
}
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