140 lines
3.8 KiB
C
140 lines
3.8 KiB
C
/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* https://stevens.netmeister.org/631/
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*/
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/* This program illustrates the use of the various
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* 'getpw*' functions. If given a username or a uid,
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* it will attempt to print the information for the
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* given user, otherwise, it will iterate over all
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* entries and print them out in /etc/passwd format.
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*
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* ./a.out 0
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* ./a.out root
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* ./a.out
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*
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* Btw, what happens when you run this program as root?
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*/
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/* We pulled in some code from id(1):
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*
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* Copyright (c) 1991, 1993
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*/
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#include <assert.h>
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#include <err.h>
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#include <errno.h>
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#include <limits.h>
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#include <pwd.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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struct passwd *who(char *);
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void printAllEntries(void);
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void printOneStruct(const struct passwd *pw);
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struct passwd *
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who(char *u)
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{
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struct passwd *pw;
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long id;
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char *ep;
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/* Translate user argument into a pw pointer.
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* First, try to get it as specified. If that
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* fails, try it as a number. */
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if ((pw = getpwnam(u)) != NULL) {
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return pw;
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}
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id = strtol(u, &ep, 10);
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if (*u && !*ep && (pw = getpwuid(id))) {
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return pw;
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}
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errx(EXIT_FAILURE, "%s: No such user", u);
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/* NOTREACHED */
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return NULL;
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}
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void
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printAllEntries(void) {
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struct passwd *pw;
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errno = 0;
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while ((pw = getpwent()) != NULL) {
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printOneStruct(pw);
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}
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if (errno) {
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fprintf(stderr, "%s: Unable to call getpwent(3): %s\n",
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getprogname(), strerror(errno));
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exit(EXIT_FAILURE);
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}
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/* We're exiting after this call, so the
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* kernel would close the password database
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* for us, but since we want to develop
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* good coding habits, we're calling
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* endpwent(3) here just like we'd call
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* close(2) in other programs. */
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endpwent();
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}
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void
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printOneStruct(const struct passwd *pw) {
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assert(pw);
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printf("%s:%s:%d:%d:%s:%s:%s\n", pw->pw_name, pw->pw_passwd,
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pw->pw_uid, pw->pw_gid,
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pw->pw_gecos, pw->pw_dir,
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pw->pw_shell);
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}
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int
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main(int argc, char ** argv)
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{
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(void)setprogname(argv[0]);
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if (argc > 2) {
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fprintf(stderr, "Usage: %s [name|uid]\n", getprogname());
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exit(EXIT_FAILURE);
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}
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if (argc == 2) {
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printOneStruct(who(argv[1]));
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} else {
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printAllEntries();
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}
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return EXIT_SUCCESS;
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}
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