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+'\" 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 (date) "Linux man-pages (unreleased)"
+.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>
+.P
+.BI "struct group *getgrnam(const char *" name );
+.BI "struct group *getgrgid(gid_t " gid );
+.P
+.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
+.P
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.P
+.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 .
+.P
+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 .
+.P
+The \fIgroup\fP structure is defined in \fI<grp.h>\fP as follows:
+.P
+.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
+.P
+For more information about the fields of this structure, see
+.BR group (5).
+.P
+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 .
+.P
+The call
+.P
+.in +4n
+.EX
+sysconf(_SC_GETGR_R_SIZE_MAX)
+.EE
+.in
+.P
+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.
+.P
+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).)
+.P
+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
+.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)