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From: @(#)getgrent.3 8.2 (Berkeley) 4/19/94
$FreeBSD: src/lib/libc/gen/getgrent.3,v 1.28 2007/01/09 00:27:53 imp Exp $
.Dd October 26, 2011 .Dt GETGRENT 3 .Os .Sh NAME .Nm getgrent , .Nm getgrent_r ,
.Nm getgrnam , .Nm getgrnam_r , .Nm getgrgid , .Nm getgrgid_r , .Nm getgruuid , .Nm getgruuid_r , .Nm setgroupent , .Nm setgrent , .Nm endgrent .Nd group database operations .Sh LIBRARY .Lb libc .Sh SYNOPSIS n grp.h n uuid/uuid.h .Ft struct group * .Fn getgrent void .Ft int
.Fn getgrent_r "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result"
.Ft struct group * .Fn getgrnam "const char *name" .Ft int .Fn getgrnam_r "const char *name" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result" .Ft struct group * .Fn getgrgid "gid_t gid" .Ft int .Fn getgrgid_r "gid_t gid" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result" .Ft int .Fn getgruuid "uuid_t uuid" .Ft int .Fn getgruuid_r "uuid_t uuid" "struct group *grp" "char *buffer" "size_t bufsize" "struct group **result" .Ft int .Fn setgroupent "int stayopen" .Ft void .Fn setgrent void .Ft void .Fn endgrent void .Sh DESCRIPTION These functions operate on the group database file
These functions obtain information from .Xr opendirectoryd 8 , including records in
a /etc/group which is described in .Xr group 5 . Each line of the database is defined by the structure .Vt group found in the include file n grp.h : d -literal -offset indent struct group { char *gr_name; /* group name */ char *gr_passwd; /* group password */ gid_t gr_gid; /* group id */ char **gr_mem; /* group members */ }; .Ed
p The functions .Fn getgrnam , .Fn getgrgid , and .Fn getgruuid search the group database for the given group name pointed to by .Fa name , the group id given by .Fa gid , or the UUID given by .Fa uuid respectively, returning the first one encountered. Identical group names, group gids, or uuids may result in undefined behavior.
p Note that the groups file
a /etc/group does not contain group UUIDs. The UUID for a group may be found using .Fn mbr_gid_to_uuid .
p On Mac OS X, these routines are thread-safe and return a pointer to a thread-specific data structure. The contents of this data structure are automatically released by subsequent calls to any of these routines on the same thread, or when the thread exits. These routines are therefore unsuitable for use in libraries or frameworks, from where they may overwrite the per-thread data that the calling application expects to find as a result of its own calls to these routines. Library and framework code should use the alternative reentrant variants detailed below.
p The .Fn getgrent function sequentially reads the group database and is intended for programs that wish to step through the complete list of groups.
p The functions .Fn getgrnam_r , .Fn getgrgid_r , and .Fn getgruuid_r are alternative versions of .Fn getgrnam , .Fn getgrgid , and .Fn getgruuid respectively. The caller must provide storage for the results of the search in the .Fa grp , .Fa buffer , .Fa bufsize , and .Fa result arguments. When these functions are successful, the .Fa grp argument will be filled-in, and a pointer to that argument will be stored in .Fa result . If an entry is not found or an error occurs, .Fa result will be set to .Dv NULL .
p These functions will open the group file for reading, if necessary.
p The .Fn setgroupent function opens the file, or rewinds it if it is already open. If .Fa stayopen is non-zero, file descriptors are left open, significantly speeding functions subsequent calls. This functionality is unnecessary for .Fn getgrent as it does not close its file descriptors by default. It should also be noted that it is dangerous for long-running programs to use this functionality as the group file may be updated.
p The .Fn setgrent function is identical to .Fn setgroupent with an argument of zero.
p The .Fn endgrent function closes any open files. .Sh RETURN VALUES The functions .Fn getgrent , .Fn getgrnam , and .Fn getgrgid , return a pointer to a group structure on success or .Dv NULL if the entry is not found or if an error occurs. If an error does occur, .Va errno will be set. Note that programs must explicitly set .Va errno to zero before calling any of these functions if they need to distinguish between a non-existent entry and an error. The functions .Fn getgrnam_r , .Fn getgrgid_r , and .Fn getgruuid_r return 0 if no error occurred, or an error number to indicate failure. It is not an error if a matching entry is not found. (Thus, if .Fa result is set to .Dv NULL and the return value is 0, no matching entry exists.)
p
.Fn setgroupent
returns the value 1 if successful, otherwise the value
0 is returned.
The functions
.Fn setgrent ,
.Fn endgrent ,
and
.Fn setgrfile
have no return value.
.Sh FILES
l -tag -width /etc/group -compact t Pa /etc/group group database file
.El
.Sh COMPATIBILITY
The historic function
.Fn setgrfile ,
which allowed the specification of alternate group databases, has
been deprecated and is no longer available.
.Sh SEE ALSO
.Xr getpwent 3 ,
.Xr group 5 ,
.Xr mbr_gid_to_uuid 3,
.Xr opendirectory 8 ,
.Xr yp 8
.Sh STANDARDS
The
.Fn getgrent ,
.Fn getgrnam ,
.Fn getgrnam_r ,
.Fn getgrgid ,
.Fn getgrgid_r
and
.Fn endgrent
functions conform to
.St -p1003.1-96 .
The
.Fn setgrent
function differs from that standard in that its return type is
.Vt int
rather than
.Vt void .
.Sh HISTORY
The functions
.Fn endgrent ,
.Fn getgrent ,
.Fn getgrnam ,
.Fn getgrgid ,
and
.Fn setgrent
appeared in
.At v7 .
The functions
.Fn setgrfile
and
.Fn setgroupent
appeared in
x 4.3 Reno . The functions
.Fn getgrent_r ,
.Fn getgrnam_r ,
.Fn getgrnam_r
and
.Fn getgrgid_r
appeared in
.Fx 5.1 .
The functions
.Fn getgruuid
and
.Fn getgruuid_r
appeared in Mac OS X 10.8.
.Sh BUGS
The functions
.Fn getgrent ,
.Fn getgrnam ,
.Fn getgrgid ,
.Fn getgruuid ,
.Fn setgroupent
and
.Fn setgrent
leave their results in an internal thread-specific memory and return
a pointer to that object.
Subsequent calls to
the same function
will modify the same object.