getgrent.3

来自「<B>Digital的Unix操作系统VAX 4.2源码</B>」· 3 代码 · 共 150 行

.\" SCCSID: @(#)getgrent.3	8.2	1/28/91
.\"
.TH getgrent 3 
.SH Name
getgrent, getgrgid, getgrnam, setgrent, endgrent \- get group entry
.SH Syntax
.nf
.B #include <grp.h>
.PP
.B struct group *getgrent()
.PP
.B struct group *getgrgid(\fIgid\fP)
.B gid_t \fIgid\fP;
.PP
.B struct group *getgrnam(\fIname\fP)
.B char *\fIname\fP;
.PP
.B void setgrent()
.PP
.B void endgrent()
.fi
.SH Description
.NXR "getgrent subroutine"
.NXR "getgrgid subroutine"
.NXR "getgrnam subroutine"
.NXR "setgrent subroutine"
.NXR "endgrent subroutine"
.NXR "group file (general)" "getting entry"
The
.PN getgrent ,
.PN getgrgid
and
.PN getgrnam
subroutines each return pointers
to an object
with the following structure
containing the broken-out
fields of a line in the group database:
.EX

struct  group { /* see getgrent(3) */
        char    *gr_name;
        char    *gr_passwd;
        int     gr_gid;
        char    **gr_mem;
};

struct group *getgrent(), *getgrgid(), *getgrnam();

.EE
.PP
The members of this structure are:
.TP \w'gr_passwd'u+2n
gr_name
The name of the group.
.br
.ns
.TP \w'gr_passwd'u+2n
gr_passwd
The encrypted password of the group.
.br
.ns
.TP \w'gr_passwd'u+2n
gr_gid
The numerical group-ID.
.br
.ns
.TP \w'gr_passwd'u+2n
gr_mem
Null-terminated vector
of pointers to the individual
member names.
.PP
A call to
.PN setgrent
has the effect of rewinding
the group file
to allow
repeated searches.
The
.PN endgrent
may be called to
close the group database
when processing is complete.
.PP
The
.PN getgrent
subroutine simply reads the next
line while
.PN getgrgid
and
.PN getgrnam
search until a matching
.I gid
or
.I name
is found
(or until EOF is encountered).
The
.PN getgrent
subroutine keeps a pointer in the database, allowing
successive calls to be used 
to search the entire file.
.PP
A call to 
.PN setgrent
must be made before a 
.PN while
loop using 
.PN getgrent
in order to perform initialization and an
.PN endgrent
must be used after the loop.  Both
.PN getgrgid
and 
.PN getgrnam
make calls to 
.PN setgrent 
and 
.PN endgrent .
.SH Restrictions
.NXR "getgrent subroutine" "restrictions"
All information
is contained in a static area
so it must be copied if it is
to be saved.
.PP
If YP is running, 
.PN getgrent
does not return the entries in any particular order.
See the 
.I Guide to the Yellow Pages Service 
for setup information.
.PP
The group database may also be distributed via the BIND/Hesiod
naming service.  See the
.I Guide to the BIND/Hesiod Service
for more information.
.SH Return Values
A null pointer
(0) is returned on EOF or error.
.SH Files
.PN /etc/group
.SH See Also
group(5), svc.conf(5)
.br
.I Guide to the BIND/Hesiod Service
.br
.I Guide to the Yellow Pages Service