Originální popis anglicky:
setaliasent, endaliasent, getaliasent, getaliasent_r, getaliasbyname,
getaliasbyname_r - read an alias entry
Návod, kniha: access mail aliases database
#include <aliases.h>
void setaliasent(void);
void endaliasent(void);
struct aliasent *getaliasent(void);
int getaliasent_r(struct aliasent *result,
char *buffer, size_t buflen, struct aliasent
**res);
struct aliasent *getaliasbyname(const char *name);
int getaliasbyname_r(const char *name,
struct aliasent *result,
char *buffer, size_t buflen, struct aliasent
**res);
One of the databases available with the Name Service Switch (NSS) is the aliases
database, that contains mail aliases. (To find out which databases are
supported, try getent --help .) Six functions are provided to access the
aliases database.
The
getaliasent() function returns a pointer to a structure containing
the group information from the aliases database. The first time it is called
it returns the first entry; thereafter, it returns successive entries.
The
setaliasent() function rewinds the file pointer to the beginning of
the aliases database.
The
endaliasent() function closes the aliases database.
getaliasent_r() is the reentrant version of the previous function. The
requested structure is stored via the first argument but the programmer needs
to fill the other arguments also. Not providing enough space causes the
function to fail.
The function
getaliasbyname() takes the name argument and searches the
aliases database. The entry is returned as a pointer to a struct aliasent.
getaliasbyname_r() is the reentrant version of the previous function. The
requested structure is stored via the second argument but the programmer need
to fill the other arguments also. Not providing enough space causes the
function to fail.
The struct aliasent is defined in <aliases.h>.
struct aliasent {
char *alias_name; /* alias name */
size_t alias_members_len;
char **alias_members; /* alias name list */
int alias_local;
};
The default alias database is the file
/etc/aliases. This can be changed
in the
/etc/nsswitch.conf file.
The functions
getaliasent_r() and
getaliasbyname_r() return a
non-zero value on error.
The following example compiles with gcc example.c -o example . It will dump all
names in the alias database.
#include <aliases.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
int main() {
struct aliasent *al;
setaliasent();
for (;;) {
al = getaliasent();
if (al == NULL) break;
printf("Name: %s\n", al->alias_name);
}
if (errno) {
perror("reading alias");
exit(EXIT_FAILURE);
}
endaliasent();
exit(EXIT_SUCCESS);
}
These routines are glibc-specific. The NeXT has similar routines
#include <aliasdb.h>
void alias_setent(void);
void alias_endent(void);
alias_ent *alias_getent(void);
alias_ent *alias_getbyname(char *name);
getgrent(3),
getpwent(3),
getspent(3),
aliases(5)
