.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\" 
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\" 
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\"
.\" References consulted:
.\"     Linux libc source code
.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
.\"     386BSD man pages
.\"
.\" Modified 1993-07-24 by Rik Faith (faith@cs.unc.edu)
.\" Modified 2003-11-15 by aeb
.\"
.TH GETGRNAM 3 2003-11-15 "" "Linux Programmer's Manual"
.SH NAME
getgrnam, getgrnam_r, getgrgid, getgrgid_r \- get group file entry
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <grp.h>
.sp
.BI "struct group *getgrnam(const char *" name );
.sp
.BI "struct group *getgrgid(gid_t " gid );
.sp
.BI "int getgrnam_r(const char *" name ", struct group *" gbuf ,
.br
.BI "          char *" buf ", size_t " buflen ", struct group **" gbufp );
.sp
.BI "int getgrgid_r(gid_t " gid ", struct group *" gbuf ,
.br
.BI "          char *" buf ", size_t " buflen ", struct group **" gbufp );
.fi
.SH DESCRIPTION
The
.B getgrnam()
function returns a pointer to a structure containing
the group information from
.I /etc/group
for the entry that matches the group name
.IR name .
.PP
The
.B getgrgid()
function returns a pointer to a structure containing
the group information from
.I /etc/group
for the entry that matches the group gid
.IR gid .
.PP
The
.B getgrnam_r()
and
.B getgrgid_r()
functions find the same information, but store the retrieved group structure
in the space pointed to by
.IR gbuf .
This group structure contains pointers to strings, and these strings
are stored in the buffer
.I buf
of size
.IR buflen .
A pointer to the result (in case of success) or NULL (in case no entry
was found or an error occurred) is stored in
.RI * gbufp .
.PP
The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
.sp
.RS
.nf
struct group {
      char    *gr_name;      /* group name */
      char    *gr_passwd;    /* group password */
      gid_t   gr_gid;        /* group id */
      char    **gr_mem;      /* group members */
};
.fi
.RE
.PP
The maximum needed size for
.I buf
can be found using
.BR sysconf (3)
with the _SC_GETGR_R_SIZE_MAX parameter.
.SH "RETURN VALUE"
The \fBgetgrnam()\fP and \fBgetgrgid()\fP functions return a pointer
to the group information structure, or NULL if the matching entry
is not found or an error occurs. If an error occurs,
.I errno
is set appropriately. If one wants to check
.I errno
after the call, it should be set to zero before the call.
.LP
The return value may point to static area, and may be overwritten
by subsequent calls to
.BR getgrent() ,
.BR getgrgid() ,
or
.BR getgrnam() .
.LP
The  \fBgetgrnam_r()\fP and \fBgetgrgid_r()\fP functions return
zero on success. In case of error, an error value is returned.
.SH ERRORS
.TP
.BR 0 " or " ENOENT " or " ESRCH " or " EBADF " or " EPERM " or ... "
The given
.I name
or
.I gid
was not found.
.TP
.B EINTR
A signal was caught.
.TP
.B EIO
I/O error.
.TP
.B EMFILE
The maximum number (OPEN_MAX) of files was open already in the calling process.
.TP
.B ENFILE
The maximum number of files was open already in the system.
.TP
.B ENOMEM
Insufficient memory.
.\" to allocate the group structure, or to allocate buffers
.TP
.B ERANGE
Insufficient buffer space supplied.
.SH FILES
.TP
.I /etc/group
group database file
.SH "CONFORMING TO"
SVID 3, BSD 4.3, POSIX 1003.1-2003
.SH NOTES
The formulation given above under "RETURN VALUE" is from POSIX 1003.1-2001.
It does not call "not found" an error, hence does not specify what value
.I errno
might have in this situation. But that makes it impossible to recognize
errors. One might argue that according to POSIX
.I errno
should be left unchanged if an entry is not found. Experiments on various
Unix-like systems shows that lots of different values occur in this
situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.
.\" more precisely:
.\" AIX 5.1 - gives ESRCH
.\" OSF1 4.0g - gives EWOULDBLOCK
.\" libc, glibc, Irix 6.5 - give ENOENT
.\" FreeBSD 4.8, OpenBSD 3.2, NetBSD 1.6 - give EPERM
.\" SunOS 5.8 - gives EBADF
.\" Tru64 5.1b, HP-UX-11i, SunOS 5.7 - give 0
.SH "SEE ALSO"
.BR endgrent (3),
.BR fgetgrent (3),
.BR getgrent (3),
.BR getpwnam (3),
.BR setgrent (3),
.BR group (5)