Line data    Source code

       1              : // Copyright (c) 2025  Made to Order Software Corp.  All Rights Reserved
       2              : //
       3              : // https://snapwebsites.org/project/snapdev
       4              : // contact@m2osw.com
       5              : //
       6              : // This program is free software: you can redistribute it and/or modify
       7              : // it under the terms of the GNU General Public License as published by
       8              : // the Free Software Foundation, either version 3 of the License, or
       9              : // (at your option) any later version.
      10              : //
      11              : // This program is distributed in the hope that it will be useful,
      12              : // but WITHOUT ANY WARRANTY; without even the implied warranty of
      13              : // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      14              : // GNU General Public License for more details.
      15              : //
      16              : // You should have received a copy of the GNU General Public License
      17              : // along with this program.  If not, see <https://www.gnu.org/licenses/>.
      18              : #pragma once
      19              : 
      20              : /** \file
      21              :  * \brief Get the current user's name.
      22              :  *
      23              :  * There is always a current user on a Unix system. If 0, it is the root
      24              :  * user. Otherwise, it is at least a UID (user identifier) and the UID
      25              :  * may be mapped to a user name through the /etc/passwd file.
      26              :  *
      27              :  * This function helps in retrieving that name which may or may not
      28              :  * be in the USER environment variable (i.e. in a CRON environment,
      29              :  * the USER variable needs to be explicitly set).
      30              :  */
      31              : 
      32              : // self
      33              : //
      34              : #include    <snapdev/static_to_dynamic_buffer.h>
      35              : 
      36              : 
      37              : // libexcept
      38              : //
      39              : //#include    "libexcept/exception.h"
      40              : 
      41              : 
      42              : // C++
      43              : //
      44              : //#include    <algorithm>
      45              : #include    <string>
      46              : //#include    <cstdint>
      47              : //#include    <iomanip>
      48              : 
      49              : 
      50              : // C
      51              : //
      52              : #include    <pwd.h>
      53              : #include    <unistd.h>
      54              : 
      55              : 
      56              : 
      57              : namespace snapdev
      58              : {
      59              : 
      60              : 
      61              : 
      62              : /** \brief Retrieve the name of the specified user.
      63              :  *
      64              :  * This function retrieve the name of the specified user. If the name cannot
      65              :  * be gathered, then the function returns an empty string.
      66              :  *
      67              :  * This function takes a user identifier and converts it to a user name.
      68              :  * By default, it uses the getuid() function. If you want to use a different
      69              :  * UID, make sure to pass the parameter as required.
      70              :  *
      71              :  * In effect, by default, the function is equivalent to:
      72              :  *
      73              :  * \code
      74              :  * char const * username(getenv("USER"));
      75              :  * \endcode
      76              :  *
      77              :  * assuming the USER variable is defined properly.
      78              :  *
      79              :  * On return, if the user was not found, errno should be set to ENOENT.
      80              :  * Other errors may occur (interrupt, I/O, permissions, too many files
      81              :  * opened, not enough memory).
      82              :  *
      83              :  * \param[in] uid  The user identifier.
      84              :  *
      85              :  * \return The name of the user if available, an empty string otherwise.
      86              :  */
      87            6 : inline std::string username(uid_t uid = ::getuid())
      88              : {
      89            6 :     static_to_dynamic_buffer<char> buf;
      90              :     for(;;)
      91              :     {
      92            6 :         struct passwd p;
      93            6 :         struct passwd * result(nullptr);
      94            6 :         int const r(getpwuid_r(uid, &p, buf.get(), buf.size(), &result));
      95            6 :         if(r == 0)
      96              :         {
      97            5 :             if(result != nullptr)
      98              :             {
      99           15 :                 return p.pw_name;
     100              :             }
     101            0 :             errno = ENOENT;
     102            0 :             break;
     103              :         }
     104            1 :         if(r != ERANGE)
     105              :         {
     106            1 :             if(r == ENOMEM)
     107              :             {
     108            0 :                 throw std::bad_alloc();
     109              :             }
     110            1 :             break;
     111              :         }
     112              :         buf.increase_size(1024);        // LCOV_EXCL_LINE
     113              :     }                                   // LCOV_EXCL_LINE
     114              : 
     115            1 :     return std::string();
     116            6 : }
     117              : 
     118              : 
     119              : 
     120              : } // namespace snapdev
     121              : // vim: ts=4 sw=4 et