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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | FILES | ATTRIBUTES | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON |
SETALIASENT(3) Linux Programmer's Manual SETALIASENT(3)
setaliasent, endaliasent, getaliasent, getaliasent_r, getaliasbyname,
getaliasbyname_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.
For an explanation of the terms used in this section, see
attributes(7).
┌────────────────────┬───────────────┬────────────────┐
│Interface │ Attribute │ Value │
├────────────────────┼───────────────┼────────────────┤
│setaliasent(), │ Thread safety │ MT-Safe locale │
│endaliasent(), │ │ │
│getaliasent_r(), │ │ │
│getaliasbyname_r() │ │ │
├────────────────────┼───────────────┼────────────────┤
│getaliasent(), │ Thread safety │ MT-Unsafe │
│getaliasbyname() │ │ │
└────────────────────┴───────────────┴────────────────┘
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 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
GNU 2015-07-23 SETALIASENT(3)
Pages that refer to this page: getent(1), nsswitch.conf(5)