.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 
.TH "GETPWUID" 3P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\" getpwuid 
.SH 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.
.SH NAME
getpwuid, getpwuid_r \- search user database for a user ID
.SH SYNOPSIS
.LP
\fB#include <pwd.h>
.br
.sp
struct passwd *getpwuid(uid_t\fP \fIuid\fP\fB);
.br
\fP
.LP
\fBint getpwuid_r(uid_t\fP \fIuid\fP\fB, struct passwd *\fP\fIpwd\fP\fB,
char
*\fP\fIbuffer\fP\fB,
.br
\ \ \ \ \ \  size_t\fP \fIbufsize\fP\fB, struct passwd **\fP\fIresult\fP\fB);
\fP
\fB
.br
\fP
.SH DESCRIPTION
.LP
The \fIgetpwuid\fP() function shall search the user database for an
entry with a matching \fIuid\fP.
.LP
The \fIgetpwuid\fP() function need not be reentrant. A function that
is not required to be reentrant is not required to be
thread-safe.
.LP
Applications wishing to check for error situations should set \fIerrno\fP
to 0 before calling \fIgetpwuid\fP(). If
\fIgetpwuid\fP() returns a null pointer and \fIerrno\fP is set to
non-zero, an error occurred.
.LP
The \fIgetpwuid_r\fP() function shall update the \fBpasswd\fP structure
pointed to by \fIpwd\fP and store a pointer to that
structure at the location pointed to by \fIresult\fP. The structure
shall contain an entry from the user database with a matching
\fIuid\fP. Storage referenced by the structure is allocated from the
memory provided with the \fIbuffer\fP parameter, which is
\fIbufsize\fP bytes in size. The maximum size needed for this buffer
can be determined with the {_SC_GETPW_R_SIZE_MAX} \fIsysconf\fP()
parameter. A NULL pointer shall be returned at the location pointed
to by
\fIresult\fP on error or if the requested entry is not found. 
.SH RETURN VALUE
.LP
The \fIgetpwuid\fP() function shall return a pointer to a \fBstruct
passwd\fP with the structure as defined in \fI<pwd.h>\fP 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, \fIerrno\fP shall
be set to indicate the error.
.LP
The return value may point to a static area which is overwritten by
a subsequent call to \fIgetpwent\fP(), \fIgetpwnam\fP(), or
\fIgetpwuid\fP().
.LP
If successful, the \fIgetpwuid_r\fP() function shall return zero;
otherwise, an error number shall be returned to indicate the
error. 
.SH ERRORS
.LP
The \fIgetpwuid\fP() and \fIgetpwuid_r\fP() functions may fail if:
.TP 7
.B EIO
An I/O error has occurred.
.TP 7
.B EINTR
A signal was caught during \fIgetpwuid\fP().
.TP 7
.B EMFILE
{OPEN_MAX} file descriptors are currently open in the calling process.
.TP 7
.B ENFILE
The maximum allowable number of files is currently open in the system.
.sp
.LP
The \fIgetpwuid_r\fP() function may fail if:
.TP 7
.B ERANGE
Insufficient storage was supplied via \fIbuffer\fP and \fIbufsize\fP
to contain the data to be referenced by the resulting
\fBpasswd\fP structure. 
.sp
.LP
\fIThe following sections are informative.\fP
.SH EXAMPLES
.SS Getting an Entry for the Root User
.LP
The following example gets the user database entry for the user with
user ID 0 (root).
.sp
.RS
.nf

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

pwd = getpwuid(id);
\fP
.fi
.RE
.SS Finding the Name for the Effective User ID
.LP
The following example defines \fIpws\fP as a pointer to a structure
of type \fBpasswd\fP, which is used to store the structure
pointer returned by the call to the \fIgetpwuid\fP() function. The
\fIgeteuid\fP()
function shall return the effective user ID of the calling process;
this is used as the search criteria for the \fIgetpwuid\fP()
function. The call to \fIgetpwuid\fP() shall return a pointer to the
structure containing that user ID value.
.sp
.RS
.nf

\fB#include <unistd.h>
#include <sys/types.h>
#include <pwd.h>
\&...
struct passwd *pws;
pws = getpwuid(geteuid());
\fP
.fi
.RE
.SS Finding an Entry in the User Database
.LP
The following example uses \fIgetpwuid\fP() to search the user database
for a user ID that was previously stored in a
\fBstat\fP 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.
.sp
.RS
.nf

\fB#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);
\fP
.fi
.RE
.SH APPLICATION USAGE
.LP
Three names associated with the current process can be determined:
\fIgetpwuid\fP( \fIgeteuid\fP()) returns the name associated with
the effective user ID of the process; \fIgetlogin\fP() returns the
name associated with the current login activity; and
\fIgetpwuid\fP( \fIgetuid\fP()) returns the name associated with the
real user ID of the
process.
.LP
The \fIgetpwuid_r\fP() 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.
.SH RATIONALE
.LP
None.
.SH FUTURE DIRECTIONS
.LP
None.
.SH SEE ALSO
.LP
\fIgetpwnam\fP(), \fIgeteuid\fP(), \fIgetuid\fP(), \fIgetlogin\fP(),
the Base Definitions volume of
IEEE\ Std\ 1003.1-2001, \fI<limits.h>\fP, \fI<pwd.h>\fP, \fI<sys/types.h>\fP
.SH 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 .