diff options
Diffstat (limited to 'manual/users.texi')
| -rw-r--r-- | manual/users.texi | 52 |
1 files changed, 49 insertions, 3 deletions
diff --git a/manual/users.texi b/manual/users.texi index d13139c4c5..406e48bfb5 100644 --- a/manual/users.texi +++ b/manual/users.texi @@ -454,10 +454,10 @@ The calling process is not privileged. @comment grp.h @comment BSD -@deftypefun int initgroups (const char *@var{user}, gid_t @var{gid}) +@deftypefun int initgroups (const char *@var{user}, gid_t @var{group}) The @code{initgroups} function sets the process's supplementary group -IDs to be the normal default for the user name @var{user}. If @var{gid} -is not -1, it includes that group also. +IDs to be the normal default for the user name @var{user}. The group +@var{group} is automatically included. This function works by scanning the group database for all the groups @var{user} belongs to. It then calls @code{setgroups} with the list it @@ -467,6 +467,52 @@ The return values and error conditions are the same as for @code{setgroups}. @end deftypefun +If you are interested in the groups a particular user belongs to, but do +not want to change the process's supplementary group IDs, you can use +@code{getgrouplist}. To use @code{getgrouplist}, your programs should +include the header file @file{grp.h}. +@pindex grp.h + +@comment grp.h +@comment BSD +@deftypefun int getgrouplist (const char *@var{user}, gid_t @var{group}, gid_t *@var{groups}, int *@var{ngroups}) +The @code{getgrouplist} function scans the group database for all the +groups @var{user} belongs to. Up to *@var{ngroups} group IDs +corresponding to these groups are stored in the array @var{groups}; the +return value from the function is the number of group IDs actually +stored. If *@var{ngroups} is smaller than the total number of groups +found, then @code{getgrouplist} returns a value of @code{-1} and stores +the actual number of groups in *@var{ngroups}. The group @var{group} is +automatically included in the list of groups returned by +@code{getgrouplist}. + +Here's how to use @code{getgrouplist} to read all supplementary groups +for @var{user}: + +@smallexample +@group +gid_t * +supplementary_groups (char *user) +@{ + int ngroups = 16; + gid_t *groups + = (gid_t *) xmalloc (ngroups * sizeof (gid_t)); + struct passwd *pw = getpwnam (user); + + if (pw == NULL) + return NULL; + + if (getgrouplist (pw->pw_name, pw->pw_gid, groups, &ngroups) < 0) + @{ + groups = xrealloc (ngroups * sizeof (gid_t)); + getgrouplist (pw->pw_name, pw->pw_gid, groups, &ngroups); + @} + return groups; +@} +@end group +@end smallexample +@end deftypefun + @node Enable/Disable Setuid @section Enabling and Disabling Setuid Access |