| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | FILES | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON | The Linux Programming Interface |
SETALIASENT(3) Linux Programmer's Manual SETALIASENT(3)
setaliasent, endaliasent, getaliasent, getaliasent_r, getaliasbyname, getal-
iasbyname_r - read an alias entry
#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 needs
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 functions getaliasent_r() and getaliasbyname_r() return a nonzero value on
error.
The default alias database is the file /etc/aliases. This can be changed in
the /etc/nsswitch.conf file.
These routines are glibc-specific. The NeXT system 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);
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(void)
{
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);
}
getgrent(3), getpwent(3), getspent(3), aliases(5)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2003-09-09 SETALIASENT(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface