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

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

.\" getgrgid 

.SH NAME

getgrgid, getgrgid_r \- get group database entry for a group ID

.SH SYNOPSIS

.LP

\fB#include <grp.h>

.br

.sp

struct group *getgrgid(gid_t\fP \fIgid\fP\fB);

.br

\fP

.LP

\fBint getgrgid_r(gid_t\fP \fIgid\fP\fB, struct group *\fP\fIgrp\fP\fB,

char

*\fP\fIbuffer\fP\fB,

.br

\ \ \ \ \ \  size_t\fP \fIbufsize\fP\fB, struct group **\fP\fIresult\fP\fB);

\fP

\fB

.br

\fP

.SH DESCRIPTION

.LP

The \fIgetgrgid\fP() function shall search the group database for

an entry with a matching \fIgid\fP.

.LP

The \fIgetgrgid\fP() function need not be reentrant. A function that

is not required to be reentrant is not required to be

thread-safe.

.LP

The \fIgetgrgid_r\fP() function shall update the \fBgroup\fP structure

pointed to by \fIgrp\fP and store a pointer to that

structure at the location pointed to by \fIresult\fP. The structure

shall contain an entry from the group database with a matching

\fIgid\fP. Storage referenced by the group 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_GETGR_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

Upon successful completion, \fIgetgrgid\fP() shall return a pointer

to a \fBstruct group\fP with the structure defined in \fI<grp.h>\fP

with a matching entry if one is found. The \fIgetgrgid\fP() function

shall

return a null pointer if either the requested entry was not found,

or an error occurred. 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 \fIgetgrent\fP(), \fIgetgrgid\fP(), or \fIgetgrnam\fP().

.LP

If successful, the \fIgetgrgid_r\fP() function shall return zero;

otherwise, an error number shall be returned to indicate the

error. 

.SH ERRORS

.LP

The \fIgetgrgid\fP() and \fIgetgrgid_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 \fIgetgrgid\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 \fIgetgrgid_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

\fBgroup\fP structure. 

.sp

.LP

\fIThe following sections are informative.\fP

.SH EXAMPLES

.SS Finding an Entry in the Group Database

.LP

The following example uses \fIgetgrgid\fP() to search the group database

for a group ID that was previously stored in a

\fBstat\fP structure, then prints out the group name if it is found.

If the group is not found, the program prints the numeric

value of the group for the entry.

.sp

.RS

.nf

\fB#include <sys/types.h>

#include <grp.h>

#include <stdio.h>

\&...

struct stat statbuf;

struct group *grp;

\&...

if ((grp = getgrgid(statbuf.st_gid)) != NULL)

    printf(" %-8.8s", grp->gr_name);

else

    printf(" %-8d", statbuf.st_gid);

\&...

\fP

.fi

.RE

.SH APPLICATION USAGE

.LP

Applications wishing to check for error situations should set \fIerrno\fP

to 0 before calling \fIgetgrgid\fP(). If

\fIerrno\fP is set on return, an error occurred.

.LP

The \fIgetgrgid_r\fP() function is thread-safe and shall return 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

\fIendgrent\fP() , \fIgetgrnam\fP() , the Base Definitions volume

of

IEEE\ Std\ 1003.1-2001, \fI<grp.h>\fP, \fI<limits.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 .