linux 源码可能很简单
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/* * Copyright (C) 2013 Karel Zak <kzak@redhat.com> */ #include <stdio.h> #include <sys/types.h> #include <fcntl.h> #include <string.h> #include <unistd.h> #include <stdlib.h> #include <getopt.h> #include "c.h" #include "nls.h" #include "pathnames.h" /* * Always return EXIT_FAILURE (1), don't try to be smart! */ static void __attribute__((__noreturn__)) usage(FILE *out) { fputs(USAGE_HEADER, out); fprintf(out, _(" %s [options]\n"), program_invocation_short_name); fputs(USAGE_SEPARATOR, out); fputs(_("Politely refuse a login.\n"), out); fputs(USAGE_OPTIONS, out); fputs(USAGE_HELP, out); fputs(USAGE_VERSION, out); fprintf(out, USAGE_MAN_TAIL("nologin(8)")); exit(EXIT_FAILURE); } int main(int argc, char *argv[]) { int c, fd; static const struct option longopts[] = { { "help", 0, 0, 'h' }, { "version", 0, 0, 'V' }, { NULL, 0, 0, 0 } }; setlocale(LC_ALL, ""); bindtextdomain(PACKAGE, LOCALEDIR); textdomain(PACKAGE); while ((c = getopt_long(argc, argv, "hV", longopts, NULL)) != -1) { switch (c) { case 'h': usage(stdout); break; case 'V': printf(UTIL_LINUX_VERSION); return EXIT_FAILURE; default: usage(stderr); break; } } fd = open(_PATH_NOLOGIN_TXT, O_RDONLY); if (fd >= 0) { char buf[BUFSIZ]; ssize_t rd; while ((rd = read(fd, buf, sizeof(buf))) > 0) ignore_result( write(STDOUT_FILENO, buf, rd) ); close(fd); } else fprintf(stdout, _("This account is currently not available.\n")); return EXIT_FAILURE; } |