path: root/man3/getgrnam.3

'\" t
.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
.\"
.\" SPDX-License-Identifier: Linux-man-pages-copyleft
.\"
.\" 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 2023-07-20 "Linux man-pages 6.05.01"
.SH NAME
getgrnam, getgrnam_r, getgrgid, getgrgid_r \- get group file entry
.SH LIBRARY
Standard C library
.RI ( libc ", " \-lc )
.SH SYNOPSIS
.nf
.B #include <sys/types.h>
.B #include <grp.h>
.PP
.BI "struct group *getgrnam(const char *" name );
.BI "struct group *getgrgid(gid_t " gid );
.PP
.BI "int getgrnam_r(const char *restrict " name \
", struct group *restrict " grp ,
.BI "               char " buf "[restrict ." buflen "], size_t " buflen ,
.BI "               struct group **restrict " result );
.BI "int getgrgid_r(gid_t " gid ", struct group *restrict " grp ,
.BI "               char " buf "[restrict ." buflen "], size_t " buflen ,
.BI "               struct group **restrict " result );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR getgrnam_r (),
.BR getgrgid_r ():
.nf
    _POSIX_C_SOURCE
        || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
.fi
.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 \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
.PP
.in +4n
.EX
struct group {
    char   *gr_name;        /* group name */
    char   *gr_passwd;      /* group password */
    gid_t   gr_gid;         /* group ID */
    char  **gr_mem;         /* NULL\-terminated array of pointers
                               to names of group members */
};
.EE
.in
.PP
For more information about the fields of this structure, see
.BR group (5).
.PP
The
.BR getgrnam_r ()
and
.BR getgrgid_r ()
functions obtain the same information as
.BR getgrnam ()
and
.BR getgrgid (),
but store the retrieved
.I group
structure
in the space pointed to by
.IR grp .
The string fields pointed to by the members of the
.I group
structure 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 call
.PP
.in +4n
.EX
sysconf(_SC_GETGR_R_SIZE_MAX)
.EE
.in
.PP
returns either \-1, without changing
.IR errno ,
or an initial suggested size for
.IR buf .
(If this size is too small,
the call fails with
.BR ERANGE ,
in which case the caller can retry with a larger buffer.)
.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 to indicate the error.
If one wants to check
.I errno
after the call, it should be set to zero before the call.
.PP
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).)
.PP
On success,
.BR getgrnam_r ()
and
.BR getgrgid_r ()
return zero, and set
.I *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; see
.BR signal (7).
.TP
.B EIO
I/O error.
.TP
.B EMFILE
The per-process limit on the number of open file descriptors has been reached.
.TP
.B ENFILE
The system-wide limit on the total number of open files has been reached.
.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 ATTRIBUTES
For an explanation of the terms used in this section, see
.BR attributes (7).
.TS
allbox;
lb lb lbx
l l l.
Interface	Attribute	Value
T{
.na
.nh
.BR getgrnam ()
T}	Thread safety	T{
.na
.nh
MT-Unsafe race:grnam locale
T}
T{
.na
.nh
.BR getgrgid ()
T}	Thread safety	T{
.na
.nh
MT-Unsafe race:grgid locale
T}
T{
.na
.nh
.BR getgrnam_r (),
.BR getgrgid_r ()
T}	Thread safety	MT-Safe locale
.TE
.sp 1
.SH VERSIONS
The formulation given above under "RETURN VALUE" is from POSIX.1.
.\" POSIX.1-2001, POSIX.1-2008
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 show 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 glibc 2.6, Irix 6.5 - give ENOENT
.\" since glibc 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 STANDARDS
POSIX.1-2008.
.SH HISTORY
POSIX.1-2001, SVr4, 4.3BSD.
.SH SEE ALSO
.BR endgrent (3),
.BR fgetgrent (3),
.BR getgrent (3),
.BR getpwnam (3),
.BR setgrent (3),
.BR group (5)