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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 Sat Jul 24 19:29:54 1993 by Rik Faith (faith@cs.unc.edu)
+.TH getgrent 3 2023-07-20 "Linux man-pages 6.05.01"
+.SH NAME
+getgrent, setgrent, endgrent \- 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
+.B struct group *getgrent(void);
+.PP
+.B void setgrent(void);
+.B void endgrent(void);
+.fi
+.PP
+.RS -4
+Feature Test Macro Requirements for glibc (see
+.BR feature_test_macros (7)):
+.RE
+.PP
+.BR setgrent ():
+.nf
+ _XOPEN_SOURCE >= 500
+.\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
+ || /* glibc >= 2.19: */ _DEFAULT_SOURCE
+ || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.fi
+.PP
+.BR getgrent (),
+.BR endgrent ():
+.nf
+ Since glibc 2.22:
+ _XOPEN_SOURCE >= 500 || _DEFAULT_SOURCE
+.\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
+ glibc 2.21 and earlier
+ _XOPEN_SOURCE >= 500
+.\" || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED
+ || /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
+ || /* glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
+.fi
+.SH DESCRIPTION
+The
+.BR getgrent ()
+function returns a pointer to a structure containing
+the broken-out fields of a record in the group database
+(e.g., the local group file
+.IR /etc/group ,
+NIS, and LDAP).
+The first time
+.BR getgrent ()
+is called,
+it returns the first entry; thereafter, it returns successive entries.
+.PP
+The
+.BR setgrent ()
+function rewinds to the beginning
+of the group database, to allow repeated scans.
+.PP
+The
+.BR endgrent ()
+function is used to close the group database
+after all processing has been performed.
+.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).
+.SH RETURN VALUE
+The
+.BR getgrent ()
+function returns a pointer to a
+.I group
+structure,
+or NULL if there are no more entries or an error occurs.
+.PP
+Upon error,
+.I errno
+may be set.
+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 (),
+.BR getgrgid (3),
+or
+.BR getgrnam (3).
+(Do not pass the returned pointer to
+.BR free (3).)
+.SH ERRORS
+.TP
+.B EAGAIN
+The service was temporarily unavailable; try again later.
+For NSS backends in glibc
+this indicates a temporary error talking to the backend.
+The error may correct itself, retrying later is suggested.
+.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
+.\" not in POSIX
+.B ENOENT
+A necessary input file cannot be found.
+For NSS backends in glibc
+this indicates the backend is not correctly configured.
+.TP
+.B ENOMEM
+.\" not in POSIX
+Insufficient memory to allocate
+.I group
+structure.
+.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 getgrent ()
+T} Thread safety T{
+.na
+.nh
+MT-Unsafe race:grent
+race:grentbuf locale
+T}
+T{
+.na
+.nh
+.BR setgrent (),
+.BR endgrent ()
+T} Thread safety T{
+.na
+.nh
+MT-Unsafe race:grent locale
+T}
+.TE
+.sp 1
+.PP
+In the above table,
+.I grent
+in
+.I race:grent
+signifies that if any of the functions
+.BR setgrent (),
+.BR getgrent (),
+or
+.BR endgrent ()
+are used in parallel in different threads of a program,
+then data races could occur.
+.SH STANDARDS
+POSIX.1-2008.
+.SH HISTORY
+POSIX.1-2001, SVr4, 4.3BSD.
+.SH SEE ALSO
+.BR fgetgrent (3),
+.BR getgrent_r (3),
+.BR getgrgid (3),
+.BR getgrnam (3),
+.BR getgrouplist (3),
+.BR putgrent (3),
+.BR group (5)