getaliasent(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 4.09 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/.

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