Add jlp utility.

README.md

@@ -14,6 +14,7 @@ Contents:
         csrpubdump/ Dump the public key from an X.509
                     certificate request.
         fragment/   Print a fragment of a file.
+        jlp/        JSON linter/prettifier.
         pembody/    Print the body of a PEM certificate.
         showimp/    List the external (e.g. non-stdlib and outside the
                     current working directory) imports for a Go file.

cmd/jlp/README

@@ -0,0 +1,3 @@
+jlp
+
+This is a JSON linter / prettifier.

cmd/jlp/jlp.go

@@ -0,0 +1,95 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io/ioutil"
+
+	"github.com/kisom/goutils/lib"
+)
+
+func prettify(file string) error {
+	in, err := ioutil.ReadFile(file)
+	if err != nil {
+		lib.Warn(err, "ReadFile")
+		return err
+	}
+
+	var buf = &bytes.Buffer{}
+	err = json.Indent(buf, in, "", "    ")
+	if err != nil {
+		lib.Warn(err, "%s", file)
+		return err
+	}
+
+	err = ioutil.WriteFile(file, buf.Bytes(), 0644)
+	if err != nil {
+		lib.Warn(err, "WriteFile")
+	}
+
+	return err
+}
+
+func compact(file string) error {
+	in, err := ioutil.ReadFile(file)
+	if err != nil {
+		lib.Warn(err, "ReadFile")
+		return err
+	}
+
+	var buf = &bytes.Buffer{}
+	err = json.Compact(buf, in)
+	if err != nil {
+		lib.Warn(err, "%s", file)
+		return err
+	}
+
+	err = ioutil.WriteFile(file, buf.Bytes(), 0644)
+	if err != nil {
+		lib.Warn(err, "WriteFile")
+	}
+
+	return err
+}
+
+func usage() {
+	progname := lib.ProgName()
+	fmt.Printf(`Usage: %s [-h] files...
+	%s is used to lint and prettify (or compact) JSON files. The
+	files will be updated in-place.
+
+	Flags:
+	-c	Compact files.
+	-h	Print this help message.
+`, progname, progname)
+
+}
+
+func init() {
+	flag.Usage = usage
+}
+
+func main() {
+	var shouldCompact bool
+	flag.BoolVar(&shouldCompact, "c", false, "Compact files instead of prettifying.")
+	flag.Parse()
+
+	action := prettify
+	if shouldCompact {
+		action = compact
+	}
+
+	var errCount int
+	for _, fileName := range flag.Args() {
+		err := action(fileName)
+		if err != nil {
+			errCount++
+		}
+	}
+
+	if errCount > 0 {
+		lib.Errx(lib.ExitFailure, "Not all files succeeded.")
+	}
+}

lib/lib.go

@@ -9,6 +9,12 @@ import (
 
 var progname = filepath.Base(os.Args[0])
 
+// ProgName returns what lib thinks the program name is, namely the
+// basename of of argv0.
+func ProgName() string {
+	return progname
+}
+
 // Warnx displays a formatted error message to standard error, à la
 // warnx(3).
 func Warnx(format string, a ...interface{}) (int, error) {