NAME

       setaliasent,  endaliasent,  getaliasent,  getaliasent_r, getaliasbyname, getaliasbyname_r - read an alias
       entry

LIBRARY

       Standard C library (libc, -lc)

SYNOPSIS

       #include <aliases.h>

       void setaliasent(void);
       void endaliasent(void);

       struct aliasent *getaliasent(void);
       int getaliasent_r(struct aliasent *restrict result,
                            char buffer[restrict .buflen], size_t buflen,
                            struct aliasent **restrict res);

       struct aliasent *getaliasbyname(const char *name);
       int getaliasbyname_r(const char *restrict name,
                            struct aliasent *restrict result,
                            char buffer[restrict .buflen], size_t buflen,
                            struct aliasent **restrict 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(), endaliasent(), getaliasent_r(), getaliasbyname_r()      │ Thread safety │ MT-Safe locale │
       ├───────────────────────────────────────────────────────────────────────┼───────────────┼────────────────┤
       │getaliasent(), getaliasbyname()                                        │ Thread safety │ MT-Unsafe      │
       └───────────────────────────────────────────────────────────────────────┴───────────────┴────────────────┘

STANDARDS

       GNU.

HISTORY

       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);

EXAMPLES

       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);
       }

SEE ALSO

       getgrent(3), getpwent(3), getspent(3), aliases(5)