Problem - Kevin Tafuro

In our example code, we call endpwent( ) after every lookup operation, but this isn’t
necessary if you need to perform multiple lookups. In fact, if you know you will be
performing a large number of lookups, always calling endpwent( ) after each one is
wasteful. Any number of lookup operations may be performed safely before eventually
calling endpwent( ).
Looking up group information is similar to looking up user information. The header
file grp.h contains the declarations for the needed functions and data types. Two
functions similar to getpwnam( ) and getpwuid( ) also exist for groups:
#include
#include
struct group *getgrgid(gid_t gid);
struct group *getgrnam(const char *name);
These two functions behave as their user counterparts do. Thus, we can use them to
perform name-to-numeric-identifier mappings, and vice versa. Just as user information
lookups require a call to endpwent( ) to clean up any resources allocated during
the lookup, group information lookups require a call to endgrent( ) to do the same.
#include
#include
#include
int spc_group_getname(gid_t gid, char **name) {
struct group *gr;
if (!(gr = getgruid(gid)) ) {
endgrent( );
return -1;
}
*name = strdup(gr->gr_name);
endgrent( );
return 0;
}
int spc_group_getgid(char *name, gid_t *gid) {
struct group *gr;
if (!(gr = getgrnam(name))) {
endgrent( );
return -1;
}
*gid = gr->gr_gid;
endgrent( );
return 0;
}
Groups may contain more than a single user. Theoretically, groups may contain any
number of members, but be aware that some implementations may impose artificial
limits on the number of users that may belong to a group.
374 | Chapter 8: Authentication and Key Exchange
This is the Title of the Book, eMatter Edition
Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.