control-C handler

go/src/miller/auxents/repl/prompt.go

@@ -18,7 +18,6 @@ const ENV_SECONDARY_PROMPT = "MLR_REPL_PS2"
 const DEFAULT_PRIMARY_PROMPT = "[mlr] "
 const DEFAULT_SECONDARY_PROMPT = ""
 
-
 func getInputIsTerminal() bool {
 	return term.IsTerminal(int(os.Stdin.Fd()))
 }

go/src/miller/auxents/repl/session.go

@@ -22,7 +22,9 @@ import (
 	"fmt"
 	"io"
 	"os"
+	"os/signal"
 	"strings"
+	"syscall"
 
 	"miller/cliutil"
 	"miller/dsl/cst"
@@ -63,6 +65,12 @@ func NewRepl(
 	// types.MlrvalFromVoid().
 	runtimeState.FilterExpression = types.MlrvalFromVoid()
 
+	// For control-C handling
+	sysToSignalHandlerChannel := make(chan os.Signal, 1) // Our signal handler reads system notification here
+	appSignalNotificationChannel := make(chan bool, 1)   // Our signal handler writes this for our app to poll
+	signal.Notify(sysToSignalHandlerChannel, os.Interrupt, syscall.SIGTERM)
+	go controlCHandler(sysToSignalHandlerChannel, appSignalNotificationChannel)
+
 	return &Repl{
 		exeName:  exeName,
 		replName: replName,
@@ -80,10 +88,23 @@ func NewRepl(
 		recordReader: recordReader,
 		recordWriter: recordWriter,
 
-		runtimeState: runtimeState,
+		runtimeState:                 runtimeState,
+		sysToSignalHandlerChannel:    sysToSignalHandlerChannel,
+		appSignalNotificationChannel: appSignalNotificationChannel,
 	}, nil
 }
 
+// When the user types control-C, immediately print something to the screen,
+// then also write to a channel while long-running things like :skip and
+// :process can check it.
+func controlCHandler(sysToSignalHandlerChannel chan os.Signal, appSignalNotificationChannel chan bool) {
+	for {
+		<-sysToSignalHandlerChannel // Block until control-C notification is sent by system
+		fmt.Println("^C") // Acknowledge for user reassurance
+		appSignalNotificationChannel <- true // Let our app poll this
+	}
+}
+
 // ----------------------------------------------------------------
 func (this *Repl) handleSession(istream *os.File) {
 	this.printStartupBanner()
@@ -103,6 +124,14 @@ func (this *Repl) handleSession(istream *os.File) {
 			os.Exit(1)
 		}
 
+		// Acknowledge any control-C's, even if typed at a ready prompt
+		select {
+		case _ = <-this.appSignalNotificationChannel:
+			continue
+		default:
+			break
+		}
+
 		// This trims the trailing newline, as well as leading/trailing whitespace:
 		trimmedLine := strings.TrimSpace(line)
 

go/src/miller/auxents/repl/types.go

@@ -5,6 +5,8 @@
 package repl
 
 import (
+	"os"
+
 	"miller/cliutil"
 	"miller/dsl/cst"
 	"miller/input"
@@ -47,4 +49,8 @@ type Repl struct {
 	recordWriter output.IRecordWriter
 
 	runtimeState *runtime.State
+
+	// For control-C handling
+	sysToSignalHandlerChannel    chan os.Signal // Our signal handler reads system notification here
+	appSignalNotificationChannel chan bool // Our signal handler writes this for our app to poll
 }

go/src/miller/auxents/repl/verbs.go

@@ -350,6 +350,8 @@ func handleSkipOrProcessN(this *Repl, n int, processingNotSkipping bool) {
 			break
 		case err = <-this.errorChannel:
 			break
+		case _ = <-this.appSignalNotificationChannel: // user typed control-C
+			break
 		}
 
 		if err != nil {
@@ -398,11 +400,18 @@ func handleSkipOrProcessUntil(this *Repl, dslString string, processingNotSkippin
 	var recordAndContext *types.RecordAndContext = nil
 
 	for {
+		doubleBreak := false
 		select {
 		case recordAndContext = <-this.inputChannel:
 			break
 		case err = <-this.errorChannel:
 			break
+		case _ = <-this.appSignalNotificationChannel: // user typed control-C
+			doubleBreak = true
+			break
+		}
+		if doubleBreak {
+			break
 		}
 
 		if err != nil {
@@ -715,7 +724,7 @@ func handleHelpSingle(this *Repl, arg string) {
 
 func showREPLIntro(this *Repl) {
 	fmt.Printf(
-`The Miller REPL is an interactive counterpart to record-processing using the
+		`The Miller REPL is an interactive counterpart to record-processing using the
 put/filter DSL.
 
 Using put and filter, you can do the following:

go/todo.txt

@@ -22,6 +22,7 @@
   o make a README.md
     - rlwrap note
 
+  ! for ^C -- need a :skip xxx / :process xxx -- also online help
   ! output-specifier: write or append.
     - applies to all record-writer stuff incl strings
     - update ':help intro'
@@ -35,7 +36,6 @@
   o tilde-expand for load/open ...
     - if '~' is in the string, run it though sh -c echo ...
 
-  ? :continue / ^C -- ?!?
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