From ff990c0cf3a09e49be75d28bce4d834380c3d2db Mon Sep 17 00:00:00 2001
From: Lieuwe Rooijakkers <lieuwerooijakkers@gmail.com>
Date: Mon, 5 Aug 2024 23:44:36 +0200
Subject: staart

---
 src/staart.c | 101 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 src/staart.c

diff --git a/src/staart.c b/src/staart.c
new file mode 100644
index 0000000..c2d65f3
--- /dev/null
+++ b/src/staart.c
@@ -0,0 +1,101 @@
+#include <assert.h>
+#include <getopt.h>
+#include <pwd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "io/read_file.h"
+#include "util/debug.h"
+#include "util/error.h"
+#include "util/loop_files.h"
+#include "util/versie.h"
+
+static int gn, gc;
+
+static void usage(FILE *f) {
+  fprintf(f,
+      "Gebruik: staart [-nchV] [BESTAND]...\n"
+      "\n"
+      "Toon de laatste 10 regels van elk BESTAND naar standaard uitvoer\n"
+      "\n"
+      "  -n AANTAL   Aantal regels om weer te geven\n"
+      "  -c AANTAL   Aantal karakters om weer te geven\n"
+      "  -h          Toon deze hulptekst\n"
+      "  -V          Toon versienummer\n");
+}
+
+// Returns pointer to argument array containing the file names
+static char** parse_options(int argc, char **argv, int *n, int *c) {
+  int opt;
+  while ((opt = getopt(argc, argv, "n:c:hV")) != -1) {
+    switch (opt) {
+      case 'c':
+        *c = atoi(optarg);
+        *n = -1;
+        break;
+
+      case 'n':
+        *c = -1;
+        *n = atoi(optarg);
+        break;
+
+      case 'h':
+        usage(stdout);
+        exit(0);
+
+      case 'V':
+        drukkedoos_print_versie(stdout);
+        exit(0);
+
+      case '?':
+        usage(stderr);
+        exit(1);
+    }
+  }
+
+  return argv + optind;
+}
+
+static int process(struct filebuf *fb, char*, bool) {
+  // handle byte limits
+  if (gc != -1) {
+    assert(gc >= 0);
+    fwrite(fb->buf+fb->sz-gc, 1, gc, stdout);
+    goto done;
+  }
+
+  assert(gn >= 0);
+  size_t n = gn;
+  if (fb->buf[fb->sz - 1] == '\n') {
+    // if the file has a trailing newline, we should ignore it. So we should
+    // except one newline more
+    n += 1;
+  }
+
+  ssize_t i;
+  for (i = fb->sz - 1; i >= 0; i--) {
+    if (fb->buf[i] == '\n') n--;
+    if (n == 0) break;
+  }
+
+  if (i < 0) {
+    // we haven't encountered the maximum of newlines, write everything
+    fwrite(fb->buf, 1, fb->sz, stdout);
+    goto done;
+  }
+
+  fwrite(fb->buf + i + 1, 1, fb->sz - i, stdout);
+
+done:
+  free_filebuf(fb);
+  return 0;
+}
+
+int entry_staart(int argc, char **argv) {
+  gn = 10;
+  gc = -1;
+  char **args = parse_options(argc, argv, &gn, &gc);
+  return loop_files(args, process);
+}
-- 
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