GETPWNAM(3)                POSIX Programmer's Manual               GETPWNAM(3)



PPRROOLLOOGG
       This manual page is part of the POSIX Programmer's Manual.  The OS
       implementation of this interface may differ (consult the corresponding
       OS manual page for details of OS behavior), or the interface may not be
       implemented on OS.

NNAAMMEE
       getpwnam, getpwnam_r -- search user database for a name

SSYYNNOOPPSSIISS
       #include <pwd.h>

       struct passwd *getpwnam(const char *_n_a_m_e);
       int getpwnam_r(const char *_n_a_m_e, struct passwd *_p_w_d, char *_b_u_f_f_e_r,
           size_t _b_u_f_s_i_z_e, struct passwd **_r_e_s_u_l_t);

DDEESSCCRRIIPPTTIIOONN
       The _g_e_t_p_w_n_a_m() function shall search the user database for an entry
       with a matching _n_a_m_e.

       The _g_e_t_p_w_n_a_m() function need not be thread-safe.

       Applications wishing to check for error situations should set _e_r_r_n_o to
       0 before calling _g_e_t_p_w_n_a_m().  If _g_e_t_p_w_n_a_m() returns a null pointer and
       _e_r_r_n_o is non-zero, an error occurred.

       The _g_e_t_p_w_n_a_m___r() function shall update the ppaasssswwdd structure pointed to
       by _p_w_d and store a pointer to that structure at the location pointed to
       by _r_e_s_u_l_t.  The structure shall contain an entry from the user database
       with a matching _n_a_m_e.  Storage referenced by the structure is allocated
       from the memory provided with the _b_u_f_f_e_r parameter, which is _b_u_f_s_i_z_e
       bytes in size. A call to _s_y_s_c_o_n_f(_SC_GETPW_R_SIZE_MAX) returns either
       -1 without changing _e_r_r_n_o or an initial value suggested for the size of
       this buffer.  A null pointer shall be returned at the location pointed
       to by _r_e_s_u_l_t on error or if the requested entry is not found.

RREETTUURRNN VVAALLUUEE
       The _g_e_t_p_w_n_a_m() function shall return a pointer to a ssttrruucctt ppaasssswwdd with
       the structure as defined in _<_p_w_d_._h_> with a matching entry if found. A
       null pointer shall be returned if the requested entry is not found, or
       an error occurs. If the requested entry was not found, _e_r_r_n_o shall not
       be changed. On error, _e_r_r_n_o shall be set to indicate the error.

       The application shall not modify the structure to which the return
       value points, nor any storage areas pointed to by pointers within the
       structure. The returned pointer, and pointers within the structure,
       might be invalidated or the structure or the storage areas might be
       overwritten by a subsequent call to _g_e_t_p_w_e_n_t(), _g_e_t_p_w_n_a_m(), or
       _g_e_t_p_w_u_i_d().  The returned pointer, and pointers within the structure,
       might also be invalidated if the calling thread is terminated.

       The _g_e_t_p_w_n_a_m___r() function shall return zero on success or if the
       requested entry was not found and no error has occurred. If an error
       has occurred, an error number shall be returned to indicate the error.

EERRRROORRSS
       These functions may fail if:

       EEIIOO    An I/O error has occurred.

       EEIINNTTRR  A signal was caught during _g_e_t_p_w_n_a_m().

       EEMMFFIILLEE All file descriptors available to the process are currently
              open.

       EENNFFIILLEE The maximum allowable number of files is currently open in the
              system.

       The _g_e_t_p_w_n_a_m___r() function may fail if:

       EERRAANNGGEE Insufficient storage was supplied via _b_u_f_f_e_r and _b_u_f_s_i_z_e to
              contain the data to be referenced by the resulting ppaasssswwdd
              structure.

       _T_h_e _f_o_l_l_o_w_i_n_g _s_e_c_t_i_o_n_s _a_r_e _i_n_f_o_r_m_a_t_i_v_e_.

EEXXAAMMPPLLEESS
       Note that _s_y_s_c_o_n_f(_SC_GETPW_R_SIZE_MAX) may return -1 if there is no
       hard limit on the size of the buffer needed to store all the groups
       returned. This example shows how an application can allocate a buffer
       of sufficient size to work with _g_e_t_p_w_n_a_m___r().


           long int initlen = sysconf(_SC_GETPW_R_SIZE_MAX);
           size_t len;
           if (initlen == -1)
               /* Default initial length. */
               len = 1024;
           else
               len = (size_t) initlen;
           struct passwd result;
           struct passwd *resultp;
           char *buffer = malloc(len);
           if (buffer == NULL)
               ...handle error...
           int e;
           while ((e = getpwnam_r("someuser", &result, buffer, len, &resultp))
                   == ERANGE)
               {
               size_t newlen = 2 * len;
               if (newlen < len)
                   ...handle error...
               len = newlen;
               char *newbuffer = realloc(buffer, len);
               if (newbuffer == NULL)
                   ...handle error...
               buffer = newbuffer;
               }
           if (e != 0)
               ...handle error...
           free (buffer);

   GGeettttiinngg aann EEnnttrryy ffoorr tthhee LLooggiinn NNaammee
       The following example uses the _g_e_t_l_o_g_i_n() function to return the name
       of the user who logged in; this information is passed to the _g_e_t_p_w_n_a_m()
       function to get the user database entry for that user.


           #include <sys/types.h>
           #include <pwd.h>
           #include <unistd.h>
           #include <stdio.h>
           #include <stdlib.h>
           ...
           char *lgn;
           struct passwd *pw;
           ...
           if ((lgn = getlogin()) == NULL || (pw = getpwnam(lgn)) == NULL) {
               fprintf(stderr, "Get of user information failed.\n"); exit(1);
           }
           ...

AAPPPPLLIICCAATTIIOONN UUSSAAGGEE
       Three names associated with the current process can be determined:
       _g_e_t_p_w_u_i_d(_g_e_t_e_u_i_d()) returns the name associated with the effective user
       ID of the process; _g_e_t_l_o_g_i_n() returns the name associated with the
       current login activity; and _g_e_t_p_w_u_i_d(_g_e_t_u_i_d()) returns the name
       associated with the real user ID of the process.

       The _g_e_t_p_w_n_a_m___r() function is thread-safe and returns values in a user-
       supplied buffer instead of possibly using a static data area that may
       be overwritten by each call.

       Portable applications should take into account that it is usual for an
       implementation to return -1 from _s_y_s_c_o_n_f() indicating that there is no
       maximum for _SC_GETPW_R_SIZE_MAX.

RRAATTIIOONNAALLEE
       None.

FFUUTTUURREE DDIIRREECCTTIIOONNSS
       None.

SSEEEE AALLSSOO
       _g_e_t_p_w_u_i_d(), _s_y_s_c_o_n_f()

       The Base Definitions volume of POSIX.1-2017, <<ppwwdd..hh>>, <<ssyyss__ttyyppeess..hh>>

CCOOPPYYRRIIGGHHTT
       Portions of this text are reprinted and reproduced in electronic form
       from IEEE Std 1003.1-2017, Standard for Information Technology --
       Portable Operating System Interface (POSIX), The Open Group Base
       Specifications Issue 7, 2018 Edition, Copyright (C) 2018 by the
       Institute of Electrical and Electronics Engineers, Inc and The Open
       Group.  In the event of any discrepancy between this version and the
       original IEEE and The Open Group Standard, the original IEEE and The
       Open Group Standard is the referee document. The original Standard can
       be obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page are
       most likely to have been introduced during the conversion of the source
       files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .



IEEE/The Open Group                  2017                          GETPWNAM(3)
