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a86118d661
Previously this file would fail to compile with the following error:
$ gcc manual/examples/db.c
db.c: In function ‘main’:
db.c:37:7: error: implicit declaration of function ‘printf’ [-Wimplicit-function-declaration]
37 | printf ("Couldn't find out about user %d.\n", (int) me);
| ^~~~~~
db.c:23:1: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
22 | #include <stdlib.h>
+++ |+#include <stdio.h>
23 |
db.c:37:7: warning: incompatible implicit declaration of built-in function ‘printf’ [-Wbuiltin-declaration-mismatch]
37 | printf ("Couldn't find out about user %d.\n", (int) me);
| ^~~~~~
db.c:37:7: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
db.c:42:3: warning: incompatible implicit declaration of built-in function ‘printf’ [-Wbuiltin-declaration-mismatch]
42 | printf ("I am %s.\n", my_passwd->pw_gecos);
| ^~~~~~
db.c:42:3: note: include ‘<stdio.h>’ or provide a declaration of ‘printf’
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
71 lines
2.0 KiB
C
71 lines
2.0 KiB
C
/* User and Group Database Example
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Copyright (C) 1991-2025 Free Software Foundation, Inc.
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, see <https://www.gnu.org/licenses/>.
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*/
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#include <grp.h>
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#include <pwd.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <stdlib.h>
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#include <stdio.h>
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int
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main (void)
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{
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uid_t me;
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struct passwd *my_passwd;
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struct group *my_group;
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char **members;
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/* Get information about the user ID. */
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me = getuid ();
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my_passwd = getpwuid (me);
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if (!my_passwd)
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{
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printf ("Couldn't find out about user %d.\n", (int) me);
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exit (EXIT_FAILURE);
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}
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/* Print the information. */
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printf ("I am %s.\n", my_passwd->pw_gecos);
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printf ("My login name is %s.\n", my_passwd->pw_name);
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printf ("My uid is %d.\n", (int) (my_passwd->pw_uid));
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printf ("My home directory is %s.\n", my_passwd->pw_dir);
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printf ("My default shell is %s.\n", my_passwd->pw_shell);
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/* Get information about the default group ID. */
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my_group = getgrgid (my_passwd->pw_gid);
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if (!my_group)
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{
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printf ("Couldn't find out about group %d.\n",
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(int) my_passwd->pw_gid);
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exit (EXIT_FAILURE);
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}
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/* Print the information. */
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printf ("My default group is %s (%d).\n",
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my_group->gr_name, (int) (my_passwd->pw_gid));
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printf ("The members of this group are:\n");
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members = my_group->gr_mem;
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while (*members)
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{
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printf (" %s\n", *(members));
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members++;
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}
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return EXIT_SUCCESS;
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}
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