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



PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux implementation of this interface may differ (con-
       sult the corresponding Linux manual page for details of Linux behavior), or the  interface  may  not  be  implemented  on
       Linux.

NAME
       getpwnam, getpwnam_r - search user database for a name

SYNOPSIS
       #include <pwd.h>

       struct passwd *getpwnam(const char *name);


       int getpwnam_r(const char *name, struct passwd *pwd, char *buffer,
              size_t bufsize, struct passwd **result);


DESCRIPTION
       The getpwnam() function shall search the user database for an entry with a matching name.

       The  getpwnam()  function  need  not  be reentrant. A function that is not required to be reentrant is not required to be
       thread-safe.

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

       The  getpwnam_r()  function  shall update the passwd structure pointed to by pwd and store a pointer to that structure at
       the location pointed to by result. The structure shall contain an entry from the user  database  with  a  matching  name.
       Storage  referenced  by  the  structure is allocated from the memory provided with the buffer parameter, which is bufsize
       bytes in size. The maximum size needed for this buffer can be determined with the {_SC_GETPW_R_SIZE_MAX} sysconf() param-
       eter.  A  NULL  pointer  shall be returned at the location pointed to by result on error or if the requested entry is not
       found.

RETURN VALUE
       The getpwnam() function shall return a pointer to a struct passwd with the structure as defined in <pwd.h> with a  match-
       ing  entry  if found. A null pointer shall be returned if the requested entry is not found, or an error occurs. On error,
       errno shall be set to indicate the error.

       The return value may point to a static area which is overwritten by a subsequent call to getpwent(), getpwnam(), or getp-
       wuid().

       If  successful, the getpwnam_r() function shall return zero; otherwise, an error number shall be returned to indicate the
       error.

ERRORS
       The getpwnam() and getpwnam_r() functions may fail if:

       EIO    An I/O error has occurred.

       EINTR  A signal was caught during getpwnam().

       EMFILE {OPEN_MAX} file descriptors are currently open in the calling process.

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


       The getpwnam_r() function may fail if:

       ERANGE Insufficient storage was supplied via buffer and bufsize to contain the data to be  referenced  by  the  resulting
              passwd structure.


       The following sections are informative.

EXAMPLES
   Getting an Entry for the Login Name
       The  following  example  uses  the  getlogin() function to return the name of the user who logged in; this information is
       passed to the getpwnam() 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);
              }
              ...

APPLICATION USAGE
       Three names associated with the current process can be determined: getpwuid( geteuid()) returns the name associated  with
       the  effective  user ID of the process; getlogin() returns the name associated with the current login activity; and getp-
       wuid( getuid()) returns the name associated with the real user ID of the process.

       The getpwnam_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.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       getpwuid(), the Base Definitions volume of IEEE Std 1003.1-2001, <limits.h>, <pwd.h>, <sys/types.h>

COPYRIGHT
       Portions  of  this  text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for
       Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6,  Copy-
       right (C) 2001-2003 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.open-
       group.org/unix/online.html .



IEEE/The Open Group                                           2003                                                  GETPWNAM(3P)