[hackers] [ubase] Add mesg(1) || sin

[git]

commit 47092bd9b600d71a30af1f074742c9fe240c9176
Author: sin <s...@2f30.org>
Date:   Sat Jul 26 15:31:44 2014 +0100

    Add mesg(1)
    
    No manpage yet.

diff --git a/Makefile b/Makefile
index 37d4ec3..992c570 100644
--- a/Makefile
+++ b/Makefile
@@ -53,6 +53,7 @@ SRC = \
        login.c             \
        lsmod.c             \
        lsusb.c             \
+       mesg.c              \
        mknod.c             \
        mkswap.c            \
        mount.c             \
diff --git a/mesg.c b/mesg.c
new file mode 100644
index 0000000..a44a098
--- /dev/null
+++ b/mesg.c
@@ -0,0 +1,53 @@
+/* See LICENSE file for copyright and license details. */
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include "util.h"
+
+static void
+usage(void)
+{
+       eprintf("usage: %s [n|y]
", argv0);
+}
+
+int
+main(int argc, char *argv[])
+{
+       struct stat sb;
+       mode_t mode;
+
+       ARGBEGIN {
+       default:
+               usage();
+       } ARGEND;
+
+       if (argc > 1)
+               usage();
+
+       if (isatty(STDIN_FILENO) == 0)
+               eprintf("stdin: not a tty
");
+
+       if (fstat(STDIN_FILENO, &sb) < 0)
+               eprintf("fstat stdin:");
+
+       if (argc == 0) {
+               puts(sb.st_mode & (S_IWGRP | S_IWOTH) ? "is y" : "is n");
+               return EXIT_SUCCESS;
+       }
+
+       if (argv[0][0] == 'y')
+               mode = sb.st_mode | S_IWGRP | S_IWOTH;
+       else if (argv[0][0] == 'n')
+               mode = sb.st_mode & ~(S_IWGRP | S_IWOTH);
+       else
+               usage();
+
+       if (fchmod(STDIN_FILENO, mode) < 0)
+               eprintf("fchmod stdin:");
+
+       return EXIT_SUCCESS;
+}