libexplain  1.4.D001
libexplain/uid_from_pid.c
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00001 /*
00002  * libexplain - a library of system-call-specific strerror replacements
00003  * Copyright (C) 2013 Peter Miller
00004  * Written by Peter Miller <pmiller@opensource.org.au>
00005  *
00006  * This program is free software; you can redistribute it and/or modify it
00007  * under the terms of the GNU Lesser General Public License as published by
00008  * the Free Software Foundation; either version 3 of the License, or (at your
00009  * option) any later version.
00010  *
00011  * This program is distributed in the hope that it will be useful, but WITHOUT
00012  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
00013  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
00014  * License for more details.
00015  *
00016  * You should have received a copy of the GNU Lesser General Public License
00017  * along with this program.  If not, see <http://www.gnu.org/licenses/>.
00018  */
00019 
00020 #include <libexplain/ac/stdio.h>
00021 #include <libexplain/ac/string.h>
00022 
00023 #include <libexplain/uid_from_pid.h>
00024 
00025 
00026 uid_t
00027 explain_uid_from_pid(pid_t pid)
00028 {
00029     char filename[100];
00030     FILE *fp;
00031 
00032     snprintf(filename, sizeof(filename), "/proc/%d/status", pid);
00033     fp = fopen(filename, "r");
00034     if (!fp)
00035         return (pid_t)-1;
00036     for (;;)
00037     {
00038         int ruid;
00039         int euid;
00040         int suid;
00041         char line[200];
00042 
00043         if (!fgets(line, sizeof(line), fp))
00044             break;
00045         if (0 != memcmp(line, "Uid:", 4))
00046             continue;
00047         if (3 == sscanf(line + 4, "%d%d%d", &ruid, &euid, &suid))
00048         {
00049             fclose(fp);
00050             return euid;
00051         }
00052     }
00053     fclose(fp);
00054     return (pid_t)-1;
00055 }
00056 
00057 
00058 /* vim: set ts=8 sw=4 et : */