mirror of
https://github.com/johnkerl/miller.git
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5eb40c9e7b
* Comment style * IRecordTransformer -> RecordTransfomer * make fmt * else-return style mod * snake-case -> camel-case * Remove redundant err = nil and similar zero-value initializations. * redundant break; * bugfix * neaten * typofix * simplify/standardize init of zero-length slices * Standardize fmt.Fprintf w/ errors * fix double print of "mlr:" * neatening * Uniformize error messages * make docs * avoid shadowing package names * shorten some receiver names
94 lines
2.5 KiB
Go
94 lines
2.5 KiB
Go
package lib
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import (
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"fmt"
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"os"
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"github.com/johnkerl/miller/v6/pkg/platform"
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)
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// OpenOutboundHalfPipe returns a handle to a process. Writing to that handle
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// writes to the process' stdin. The process' stdout and stderr are the current
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// process' stdout and stderr.
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//
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// This is for pipe-output-redirection in the Miller put/filter DSL.
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//
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// Note I am not using os.exec.Cmd which is billed as being simpler than using
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// os.StartProcess. It may indeed be simpler when you want to handle the
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// subprocess' stdin/stdout/stderr all three within the parent process. Here I
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// found it much easier to use os.StartProcess to let the stdout/stderr run
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// free.
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func OpenOutboundHalfPipe(commandString string) (*os.File, error) {
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readPipe, writePipe, err := os.Pipe()
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if err != nil {
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return nil, err
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}
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var procAttr os.ProcAttr
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procAttr.Files = []*os.File{
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readPipe,
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os.Stdout,
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os.Stderr,
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}
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// /bin/sh -c "..." or cmd /c "..."
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shellRunArray := platform.GetShellRunArray(commandString)
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process, err := os.StartProcess(shellRunArray[0], shellRunArray, &procAttr)
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if err != nil {
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return nil, err
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}
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go process.Wait()
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return writePipe, nil
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}
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// OpenInboundHalfPipe returns a handle to a process. Reading from that handle
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// reads from the process' stdout. The process' stdin and stderr are the
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// current process' stdin and stderr.
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//
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// This is for the Miller prepipe feature.
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//
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// Note I am not using os.exec.Cmd which is billed as being simpler than using
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// os.StartProcess. It may indeed be simpler when you want to handle the
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// subprocess' stdin/stdout/stderr all three within the parent process. Here I
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// found it much easier to use os.StartProcess to let the stdin/stderr run
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// free.
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func OpenInboundHalfPipe(commandString string) (*os.File, error) {
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readPipe, writePipe, err := os.Pipe()
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if err != nil {
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return nil, err
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}
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var procAttr os.ProcAttr
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procAttr.Files = []*os.File{
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os.Stdin,
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writePipe,
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os.Stderr,
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}
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// /bin/sh -c "..." or cmd /c "..."
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shellRunArray := platform.GetShellRunArray(commandString)
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process, err := os.StartProcess(shellRunArray[0], shellRunArray, &procAttr)
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if err != nil {
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return nil, err
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}
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// TODO comment somewhere
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// https://stackoverflow.com/questions/47486128/why-does-io-pipe-continue-to-block-even-when-eof-is-reached
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// TODO comment
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go func(process *os.Process, readPipe *os.File) {
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_, err := process.Wait()
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if err != nil {
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fmt.Fprintf(os.Stderr, "mlr: %v\n", err)
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}
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readPipe.Close()
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}(process, readPipe)
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return readPipe, nil
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}
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