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@(#)getgrent.3 8.2 (Berkeley) 4/19/94
.Dd April 4, 2005 .Dt GETGRENT 3 .Os .Sh NAME .Nm getgrent , .Nm getgrent_r , .Nm getgrgid , .Nm getgrgid_r , .Nm getgrnam , .Nm getgrnam_r , .Nm setgroupent , .Nm setgrfile ,
.Nm setgrent , .Nm endgrent .Nd group database operations .Sh LIBRARY .Lb libc .Sh SYNOPSIS n grp.h .Ft struct group * .Fn getgrent void .Ft int .Fo getgrent_r .Fa "struct group *grp" .Fa "char *buffer" .Fa "size_t buflen" .Fa "struct group **result" .Fc .Ft struct group * .Fn getgrgid "gid_t gid" .Ft int .Fo getgrgid_r .Fa "gid_t gid" .Fa "struct group *grp" .Fa "char *buffer" .Fa "size_t buflen" .Fa "struct group **result" .Fc .Ft struct group * .Fn getgrnam "const char *name" .Ft int .Fo getgrnam_r .Fa "const char *name" .Fa "struct group *grp" .Fa "char *buffer" .Fa "size_t buflen" .Fa "struct group **result" .Fc .Ft int .Fn setgroupent "int stayopen" .Ft void
.Fn setgrfile "const char *name"
.Ft void .Fn setgrent void .Ft void .Fn endgrent void .Sh DESCRIPTION These functions operate on the group database which is described in .Xr group 5 . Each line of the database is defined by the structure .Ar group found in the include file .Aq Pa 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 and .Fn getgrgid search the group database for the given group name pointed to by .Ar name or the group id pointed to by .Ar gid , respectively, returning the first one encountered. Identical group names or group ids may result in undefined behavior.
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 All three functions will open the group file for reading, if necessary.
p The functions .Fn getgrnam_r , .Fn getgrgid_r , and .Fn getgrent_r act like their non re-entrant counterparts respectively, updating the contents of .Ar grp and storing a pointer to that in .Ar result , and returning 0. Storage used by .Ar grp is allocated from .Ar buffer , which is .Ar buflen bytes in size. If an error occurs, an error number will be returned and .Ar result will point to null. Calling .Fn getgrent_r from multiple threads will result in each thread reading a disjoint portion of the group database.
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 doesn't 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 equivalent to .Fn setgroupent with an argument of zero.
p The .Fn endgrent function closes any open files. .Sh RETURN VALUES The functions .Fn getgrgid , .Fn getgrnam , and .Fn getgrent return a pointer to the group entry if successful; if end-of-file is reached or an error occurs a null pointer is returned.
p The functions .Fn getgrgid_r , .Fn getgrnam_r , and .Fn getgrent_r return 0 if sucessful and update .Ar result to point to .Ar grp . If an error occurs an error code is returned and .Ar result will contain a null pointer.
p The .Fn setgroupent function returns the value 1 if successful, otherwise the value 0 is returned.
p The .Fn endgrent and .Fn setgrent functions have no return value. .Sh FILES l -tag -width /etc/group -compact t Pa /etc/group group database file .El .Sh SEE ALSO .Xr getpwent 3 , .Xr group 5 , .Xr nsswitch.conf 5 .Sh STANDARDS The .Fn endgrent , .Fn getgrent , .Fn getgrgid , .Fn getgrgid_r , .Fn getgrnam , .Fn getgrnam_r , and .Fn setgrent functions conform to .St -p1003.1-90 . .Sh HISTORY The functions .Fn endgrent , .Fn getgrent , .Fn getgrgid , .Fn getgrnam , and .Fn setgrent appeared in .At v7 . The functions .Fn setgrfile and .Fn setgroupent appeared in x 4.3 Reno . The functions .Fn getgrgid_r and .Fn getgrnam_r appeared in .Nx 3.0 . .Sh COMPATIBILITY The historic function .Fn setgrfile , which allowed the specification of alternative group databases, has been deprecated and is no longer available. .Sh BUGS The functions .Fn getgrent , .Fn getgrgid , .Fn getgrnam , .Fn setgroupent and .Fn setgrent leave their results in an internal static object and return a pointer to that object. Subsequent calls to the same function will modify the same object.
p The functions .Fn getgrent , .Fn endgrent , .Fn setgroupent , and .Fn setgrent are fairly useless in a networked environment and should be avoided, if possible. .Fn getgrent makes no attempt to suppress duplicate information if multiple sources are specified in .Xr nsswitch.conf 5
Indexes created Mon Nov 03 21:09:55 GMT 2025