From e978ca4e7fce8497eb9f51b1ec53b69d4e74fa2c Mon Sep 17 00:00:00 2001
From: "Zed A. Shaw" <zed.shaw@gmail.com>
Date: Sun, 3 Aug 2025 11:04:58 -0400
Subject: [PATCH] Create a simple cli opts parser.

---
 cat/main.go | 35 ++++++++++++++++++++++-------------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/cat/main.go b/cat/main.go
index 0c156e2..6a157d4 100644
--- a/cat/main.go
+++ b/cat/main.go
@@ -14,30 +14,39 @@ func Fail(err error, format string, v ...any) {
   os.Exit(1)
 }
 
-func main() {
-  var number bool
-  var squeeze bool
+type Opts struct {
+  Number bool
+  Squeeze bool
+  Filename string
+}
 
-  flag.BoolVar(&number, "n", false, "Number all nonempty output lines, starting with 1")
-  flag.BoolVar(&number, "number", false, "Number all nonempty output lines, starting with 1")
-  flag.BoolVar(&squeeze, "s", false, "Suppress repeated adjacnet blank lines")
-  flag.BoolVar(&squeeze, "squeeze-blank", false, "Suppress repeated adjacnet blank lines")
+func parse_opts() (Opts) {
+  var opts Opts
+
+  flag.BoolVar(&opts.Number, "n", false, "Number all nonempty output lines, starting with 1")
+  flag.BoolVar(&opts.Squeeze, "s", false, "Suppress repeated adjacent blank lines")
   flag.Parse()
 
   if flag.NArg() < 1 {
-    log.Fatal("USAGE: cat [-n/--number] file0 [fileN]")
+    log.Fatal("USAGE: cat [-n] [-s] file0 [fileN]")
     os.Exit(1)
   }
 
-  filename := flag.Arg(0)
-  in_file, err := os.ReadFile(filename)
+  opts.Filename = flag.Arg(0)
+
+  return opts
+}
+
+func main() {
+  opts := parse_opts()
+  in_file, err := os.ReadFile(opts.Filename)
 
-  if err != nil { Fail(err, "cannot open %s:", filename) }
+  if err != nil { Fail(err, "cannot open %s:", opts.Filename) }
 
-  if(number) {
+  if(opts.Number) {
     count := 1
     for line := range strings.Lines(string(in_file)) {
-      if squeeze && len(line) <= 1 {
+      if opts.Squeeze && len(line) <= 1 {
         continue
       }