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SETALIASENT(3)             Linux Programmer's Manual            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  pro-
       vided 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 pro-
       grammer 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 at-
       tributes(7).

       +--------------------+---------------+----------------+
       |Interface           | Attribute     | Value          |
       +--------------------+---------------+----------------+
       |setaliasent(), en-  | Thread safety | MT-Safe locale |
       |daliasent(), getal- |               |                |
       |iasent_r(), getal-  |               |                |
       |iasbyname_r()       |               |                |
       +--------------------+---------------+----------------+
       |getaliasent(),      | Thread safety | MT-Unsafe      |
       |getaliasbyname()    |               |                |
       +--------------------+---------------+----------------+
CONFORMING TO
       These routines are glibc-specific.  The NeXT system  has  similar  rou-
       tines:

           #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 5.05 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                               2019-03-06                    SETALIASENT(3)
NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | FILES | ATTRIBUTES | CONFORMING TO | EXAMPLE | SEE ALSO | COLOPHON