setaliasent(3) - Linux manual page (original) (raw)

setaliasent(3) Library Functions Manual setaliasent(3)

NAME top

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

LIBRARY top

   Standard C library (_libc_, _-lc_)

SYNOPSIS top

   **#include <aliases.h>**

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

   **struct aliasent *getaliasent(void);**
   **int getaliasent_r(struct aliasent *restrict** _result_**,**
                        **char** _buffer_**[restrict .**_size_**], size_t** _size_**,**
                        **struct aliasent restrict** _res_**);**

   **struct aliasent *getaliasbyname(const char ***_name_**);**
   **int getaliasbyname_r(const char *restrict** _name_**,**
                        **struct aliasent *restrict** _result_**,**
                        **char** _buffer_**[restrict .**_size_**], size_t** _size_**,**
                        **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)](../man7/attributes.7.html).
   ┌───────────────────────────────┬───────────────┬────────────────┐
   │ **Interface** │ **Attribute** │ **Value** │
   ├───────────────────────────────┼───────────────┼────────────────┤
   │ **setaliasent**(), **endaliasent**(), │ Thread safety │ MT-Safe locale │
   │ **getaliasent_r**(),              │               │                │
   │ **getaliasbyname_r**()            │               │                │
   ├───────────────────────────────┼───────────────┼────────────────┤
   │ **getaliasent**(),                │ Thread safety │ MT-Unsafe      │
   │ **getaliasbyname**()              │               │                │
   └───────────────────────────────┴───────────────┴────────────────┘

STANDARDS top

   GNU.

HISTORY top

   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 <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 top

   [getgrent(3)](../man3/getgrent.3.html), [getpwent(3)](../man3/getpwent.3.html), [getspent(3)](../man3/getspent.3.html), [aliases(5)](../man5/aliases.5.html)

COLOPHON top

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Linux man-pages 6.10 2024-12-24 setaliasent(3)

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