man-pages/man3/getgrnam.3

.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
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.\" 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 2009-03-30 "" "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 *" grp ,
.br
.BI "          char *" buf ", size_t " buflen ", struct group **" result );
.sp
.BI "int getgrgid_r(gid_t " gid ", struct group *" grp ,
.br
.BI "          char *" buf ", size_t " buflen ", struct group **" result );
.fi
.sp
.in -4n
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.ad l
.in
.sp
.BR getgrnam_r (),
.BR getgrgid_r ():
.RS 4
_POSIX_C_SOURCE\ >=\ 1 || _XOPEN_SOURCE || _BSD_SOURCE ||
_SVID_SOURCE || _POSIX_SOURCE
.RE
.ad b
.SH DESCRIPTION
The
.BR getgrnam ()
function returns a pointer to a structure containing
the broken-out fields of the record in the group database
(e.g., the local group file
.IR /etc/group ,
NIS, and LDAP)
that matches the group name
.IR name .
.PP
The
.BR getgrgid ()
function returns a pointer to a structure containing
the broken-out fields of the record in the group database
that matches the group ID
.IR gid .
.PP
The
.BR getgrnam_r ()
and
.BR getgrgid_r ()
functions obtain the same information, but store the retrieved
.I group
structure
in the space pointed to by
.IR grp .
This
.I 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
.IR *result .
.PP
The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
.sp
.in +4n
.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
.in
.PP
The maximum needed size for
.I buf
can be found using
.BR sysconf (3)
with the argument
.BR _SC_GETGR_R_SIZE_MAX .
.SH "RETURN VALUE"
The
.BR getgrnam ()
and
.BR getgrgid ()
functions return a pointer to a
.I group
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 a static area, and may be overwritten
by subsequent calls to
.BR getgrent (3),
.BR getgrgid (),
or
.BR getgrnam ().
(Do not pass the returned pointer to
.BR free (3).)
.LP
On success,
.BR getgrnam_r ()
and
.BR getgrgid_r ()
return zero, and set
.IR *result
to
.IR grp .
If no matching group record was found,
these functions return 0 and store NULL in
.IR *result .
In case of error, an error number is returned, and NULL is stored in
.IR *result .
.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
.RB ( 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
.\" not in POSIX
Insufficient memory to allocate
.I group
structure.
.\" to allocate the group structure, or to allocate buffers
.TP
.B ERANGE
Insufficient buffer space supplied.
.SH FILES
.TP
.I /etc/group
local group database file
.SH "CONFORMING TO"
SVr4, 4.3BSD, POSIX.1-2001.
.SH NOTES
The formulation given above under "RETURN VALUE" is from POSIX.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 up to version 2.6, Irix 6.5 - give ENOENT
.\" glibc since version 2.7 - give 0
.\" 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)