setaliasent(3) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | FILES | ATTRIBUTES | CONFORMING TO | EXAMPLES | SEE ALSO | COLOPHON

SETALIASENT(3)          Linux Programmer's Manual         SETALIASENT(3)

NAME         top

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

SYNOPSIS         top

       #include <aliases.h>

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

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

DESCRIPTION         top

       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         top

       The functions getaliasent_r() and getaliasbyname_r() return a
       nonzero value on error.

FILES         top

       The default alias database is the file /etc/aliases.  This can be
       changed in the /etc/nsswitch.conf file.

ATTRIBUTES         top

       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()               │               │                │
       └───────────────────────────────┴───────────────┴────────────────┘

CONFORMING TO         top

       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);

EXAMPLES         top

       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         top

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

COLOPHON         top

       This page is part of release 5.11 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                            2021-03-22                 SETALIASENT(3)

Pages that refer to this page: getent(1)nsswitch.conf(5)