setaliasent(3)
NAME
setaliasent, endaliasent, getaliasent, getaliasent_r, getaliasbyname, getaliasbyname_r - read an alias entry
SYNOPSIS
#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);
DESCRIPTION
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;
};
RETURN VALUE
The functions getaliasent_r() and getaliasbyname_r() return a nonzero value on error.
FILES
The default alias database is the file /etc/aliases. This can be changed in the /etc/nsswitch.conf file.
ATTRIBUTES
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() │ │ │ └────────────────────┴───────────────┴────────────────┘
CONFORMING TO
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);
EXAMPLE
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);
}
SEE ALSO
getgrent(3), getpwent(3), getspent(3), aliases(5)
COLOPHON
This page is part of release 4.09 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/.
Opportunity
Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.
Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.
Free Software
Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.
Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.
Free Books
The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.
Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.
Education
Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.
Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.
