cat : first naive version

cat/cat.go

@@ -0,0 +1,58 @@
+package cat
+
+import (
+	"fmt"
+	"log"
+	"os"
+	"strings"
+
+	"github.com/brtholomy/um/go/cmd"
+	"github.com/brtholomy/um/go/flags"
+	"github.com/brtholomy/um/go/pipe"
+)
+
+const (
+	CMD       = cmd.Cat
+	SUMMARY   = "cat um files together using a filelist"
+	SEPARATOR = "\n---\n\n"
+)
+
+type options struct {
+	Filelist flags.Arg
+	Help     flags.Flag[bool]
+}
+
+func initOpts() options {
+	return options{
+		flags.Arg{"", "filelist. accepts from stdin if not provided"},
+		flags.Flag[bool]{"--help", "-h", false, "show help"},
+	}
+}
+
+func cat(files []string) (string, error) {
+	// strings.Builder ?
+	// can we estimate needed size? do an ls -S call?
+	ff := []string{}
+	for _, f := range files {
+		dat, err := os.ReadFile(f)
+		if err != nil {
+			return "", fmt.Errorf("error opening file: %w", err)
+		}
+		ff = append(ff, string(dat))
+	}
+	return strings.Join(ff, SEPARATOR), nil
+}
+
+func Cat(args []string) {
+	opts := initOpts()
+	flags.ParseArgs(CMD, SUMMARY, args, &opts)
+	files, err := pipe.FileListSplitMaybeStdin(opts.Filelist.Val)
+	if err != nil {
+		log.Fatalf("um %s: %s", CMD, err)
+	}
+	s, err := cat(files)
+	if err != nil {
+		log.Fatalf("um %s: %s", CMD, err)
+	}
+	fmt.Println(s)
+}