|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|
|
NAME | LIBRARY | SYNOPSIS | DESCRIPTION | RETURN VALUE | FILES | ATTRIBUTES | STANDARDS | HISTORY | EXAMPLES | SEE ALSO | COLOPHON |
|
|
|
setaliasent(3) Library Functions Manual setaliasent(3)
setaliasent, endaliasent, getaliasent, getaliasent_r,
getaliasbyname, getaliasbyname_r - read an alias entry
Standard C library (libc, -lc)
#include <aliases.h>
void setaliasent(void);
void endaliasent(void);
struct aliasent *getaliasent(void);
int getaliasent_r(size_t size;
struct aliasent *restrict result,
char buffer[restrict size], size_t size,
struct aliasent **restrict res);
struct aliasent *getaliasbyname(const char *name);
int getaliasbyname_r(size_t size;
const char *restrict name,
struct aliasent *restrict result,
char buffer[restrict size], size_t size,
struct aliasent **restrict 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(), endaliasent(), │ Thread safety │ MT-Safe locale │
│ getaliasent_r(), │ │ │
│ getaliasbyname_r() │ │ │
├───────────────────────────────┼───────────────┼────────────────┤
│ getaliasent(), │ Thread safety │ MT-Unsafe │
│ getaliasbyname() │ │ │
└───────────────────────────────┴───────────────┴────────────────┘
GNU.
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 <errno.h>
#include <stdio.h>
#include <stdlib.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 the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
man-pages@man7.org
Linux man-pages 6.15 2025-06-28 setaliasent(3)
Pages that refer to this page: getent(1), nsswitch.conf(5)
|
HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
|