Reinvent the classic unix wall command

examples/wall.c

@@ -0,0 +1,148 @@
+#if 0
+/*─────────────────────────────────────────────────────────────────╗
+│ To the extent possible under law, Justine Tunney has waived      │
+│ all copyright and related or neighboring rights to this file,    │
+│ as it is written in the following disclaimers:                   │
+│   • http://unlicense.org/                                        │
+│   • http://creativecommons.org/publicdomain/zero/1.0/            │
+╚─────────────────────────────────────────────────────────────────*/
+#endif
+#include "libc/calls/calls.h"
+#include "libc/calls/struct/timespec.h"
+#include "libc/calls/termios.h"
+#include "libc/errno.h"
+#include "libc/fmt/fmt.h"
+#include "libc/runtime/runtime.h"
+#include "libc/stdio/append.h"
+#include "libc/stdio/stdio.h"
+#include "libc/str/str.h"
+#include "libc/sysv/consts/o.h"
+#include "libc/time/struct/tm.h"
+#include "third_party/getopt/getopt.h"
+#include "third_party/musl/passwd.h"
+
+/**
+ * @fileoverview program for broadcasting message to all terminals, e.g.
+ *
+ *     o//examples/wall.com hello friends
+ *
+ * Will place some bold text into the top left corners of all terminals:
+ *
+ *     Broadcast message from jart@host (pts/4) (Tue Oct 11 03:52:24 2022):
+ *     hello friends
+ *
+ * It's useful for having one terminal tab notify your other ones when
+ * something like a long running job completes. In the old days back
+ * when unix systems had multiple users, the wall command provided the
+ * ultimate lulz especially if it's a setuid binary with root privs.
+ */
+
+#define GETOPTS "v"
+#define USAGE \
+  "\
+Usage: wall.com [-v] [TEXTMSG] [<TEXTMSG]\n\
+  -v          increase verbosity\n\
+Examples:\n\
+  wall.com 'hello my friends'\n\
+  echo hello my friends | wall.com\n\
+"
+
+int g_verbose;
+
+static void GetOpts(int argc, char *argv[]) {
+  int opt;
+  while ((opt = getopt(argc, argv, GETOPTS)) != -1) {
+    switch (opt) {
+      case 'v':
+        g_verbose++;
+        break;
+      case '?':
+        write(1, USAGE, sizeof(USAGE) - 1);
+        exit(0);
+      default:
+        write(2, USAGE, sizeof(USAGE) - 1);
+        exit(64);
+    }
+  }
+}
+
+char *GetHost(void) {
+  static char host[254];
+  if (gethostname(host, sizeof(host))) {
+    strcpy(host, "localhost");
+  }
+  return host;
+}
+
+char *GetTime(void) {
+  int64_t t;
+  struct tm tm;
+  struct timespec ts;
+  clock_gettime(0, &ts);
+  localtime_r(&ts.tv_sec, &tm);
+  return _chomp(asctime(&tm));
+}
+
+int main(int argc, char *argv[]) {
+  GetOpts(argc, argv);
+
+  // create broadcast banner
+  // we use \e[1m so the text is strong & visually distinct
+  // we use \e[K so it doesn't get lost in a forest of text
+  // we map \n → \r\n because teletype might be in raw mode
+  char *msg = 0;
+  const char *s;
+  appends(&msg, "\e7");    // save cursor position
+  appends(&msg, "\e[H");   // goto top left corne
+  appends(&msg, "\e[K");   // clear line forward
+  appends(&msg, "\e[1m");  // bold text
+  appendf(&msg, "Broadcast message from %s@%s", getpwuid(getuid())->pw_name,
+          GetHost());
+  if (isatty(0) && (s = ttyname(0))) appendf(&msg, " (%s)", s);
+  appendf(&msg, " (%s):\r\n", GetTime());
+  appends(&msg, "\e[K");
+
+  // append broadcast message
+  if (optind < argc) {
+    // use cli arguments as message if they exist
+    for (int i = 0; optind + i < argc; ++i) {
+      if (i) appends(&msg, " ");
+      for (s = argv[optind + i]; *s; ++s) {
+        if (*s == '\n') {
+          appends(&msg, "\r\n\e[K");
+        } else {
+          appendw(&msg, *s & 255);
+        }
+      }
+    }
+  } else {
+    // otherwise use stdin as message
+    ssize_t i, rc;
+    char buf[512];
+    while ((rc = read(0, buf, sizeof(buf))) > 0) {
+      for (i = 0; i < rc; ++i) {
+        if (buf[i] == '\n') {
+          appends(&msg, "\r\n\e[K");  // clear line forward
+        } else {
+          appendw(&msg, buf[i] & 255);
+        }
+      }
+    }
+  }
+  appends(&msg, "\r\n\e[K\e[0m\e8");  // restore
+
+  // try to send message to all pseudoteletypewriters
+  for (int i = 0;; ++i) {
+    int fd;
+    char pts[32];
+    snprintf(pts, sizeof(pts), "/dev/pts/%d", i);
+    if ((fd = open(pts, O_WRONLY | O_NOCTTY)) == -1) {
+      if (errno == ENOENT) break;
+      if (g_verbose) perror(pts);
+    }
+    write(fd, msg, appendz(msg).i);
+    close(fd);
+  }
+
+  return 0;
+}