setaliasent

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
       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 5.04 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)