GETPWUID(3P) - phpMan

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

PROLOG
       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
       implementation of this interface may differ (consult the  corresponding
       Linux  manual page for details of Linux behavior), or the interface may
       not be implemented on Linux.
NAME
       getpwuid, getpwuid_r - search user database for a user ID
SYNOPSIS
       #include <pwd.h>
       struct passwd *getpwuid(uid_t uid);

       int getpwuid_r(uid_t uid, struct passwd *pwd, char *buffer,
              size_t bufsize, struct passwd **result);

DESCRIPTION
       The getpwuid() function shall search the user  database  for  an  entry
       with a matching uid.
       The  getpwuid()  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 getpwuid(). If getpwuid() returns a null pointer and
       errno is set to non-zero, an error occurred.
       The getpwuid_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 uid. 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 deter-
       mined with  the  {_SC_GETPW_R_SIZE_MAX}  sysconf()  parameter.  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 getpwuid() function shall return a pointer to a struct passwd  with
       the  structure  as defined in <pwd.h> with a matching 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 getpwuid().
       If successful, the getpwuid_r() function shall return zero;  otherwise,
       an error number shall be returned to indicate the error.
ERRORS
       The getpwuid() and getpwuid_r() functions may fail if:
       EIO    An I/O error has occurred.
       EINTR  A signal was caught during getpwuid().
       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 getpwuid_r() function may fail if:
       ERANGE Insufficient storage was supplied via buffer and bufsize to con-
              tain the data to be referenced by the  resulting  passwd  struc-
              ture.

       The following sections are informative.
EXAMPLES
   Getting an Entry for the Root User
       The  following  example  gets the user database entry for the user with
       user ID 0 (root).

              #include <sys/types.h>
              #include <pwd.h>
              ...
              uid_t id = 0;
              struct passwd *pwd;

              pwd = getpwuid(id);
   Finding the Name for the Effective User ID
       The following example defines pws as a pointer to a structure  of  type
       passwd,  which  is  used to store the structure pointer returned by the
       call to the getpwuid() function. The geteuid()  function  shall  return
       the  effective  user  ID  of  the  calling process; this is used as the
       search criteria for the getpwuid() function.  The  call  to  getpwuid()
       shall return a pointer to the structure containing that user ID value.

              #include <unistd.h>
              #include <sys/types.h>
              #include <pwd.h>
              ...
              struct passwd *pws;
              pws = getpwuid(geteuid());
   Finding an Entry in the User Database
       The following example uses getpwuid() to search the user database for a
       user ID that was previously stored in a stat structure, then prints out
       the  user  name  if it is found.  If the user is not found, the program
       prints the numeric value of the user ID for the entry.

              #include <sys/types.h>
              #include <pwd.h>
              #include <stdio.h>
              ...
              struct stat statbuf;
              struct passwd *pwd;
              ...
              if ((pwd = getpwuid(statbuf.st_uid)) != NULL)
                  printf(" %-8.8s", pwd->pw_name);
              else
                  printf(" %-8d", statbuf.st_uid);
APPLICATION USAGE
       Three names associated with the current process can be determined: get-
       pwuid(  geteuid())  returns the name associated with the effective user
       ID of the process; getlogin() returns the name associated with the cur-
       rent  login  activity; and getpwuid( getuid()) returns the name associ-
       ated with the real user ID of the process.
       The getpwuid_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
       getpwnam(), geteuid(), getuid(), getlogin(), the Base Definitions  vol-
       ume 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, Copyright (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.opengroup.org/unix/online.html .

IEEE/The Open Group                  2003                         GETPWUID(3P)