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.\" Copyright (c) 2001-2003 The Open Group, All Rights Reserved 

.TH "GETPWUID" P 2003 "IEEE/The Open Group" "POSIX Programmer's Manual"

.\" getpwuid 

.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 .