man3/setaliasent.3

   1 .\" Copyright 2003 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\" Distributed under GPL
   3 .\"
   4 .\" Polished a bit, added a little, aeb
   5 .\"
   6 .TH SETALIASENT 3 2003-09-09 "GNU" "access mail aliases database"
   7 .SH NAME
   8 setaliasent, endaliasent, getaliasent, getaliasent_r,
   9 getaliasbyname, getaliasbyname_r \- read an alias entry
  10 .SH SYNOPSIS
  11 .B #include <aliases.h>
  12 .sp
  13 .BI "void setaliasent(void);"
  14 .sp
  15 .BI "void endaliasent(void);"
  16 .sp
  17 .BI "struct aliasent *getaliasent(void);"
  18 .sp
  19 .BI "int getaliasent_r(struct aliasent *" result ","
  20 .br
  21 .BI "    char *" buffer ", size_t " buflen ", struct aliasent **" res );
  22 .sp
  23 .BI "struct aliasent *getaliasbyname(const char *" name );
  24 .sp
  25 .BI "int getaliasbyname_r(const char *" name ,
  26 .br
  27 .BI "    struct aliasent *" result ,
  28 .br
  29 .BI "    char *" buffer ", size_t " buflen ", struct aliasent **" res );
  30 .sp
  31 .SH DESCRIPTION
  32 One of the databases available with the Name Service Switch (NSS)
  33 is the aliases database, that contains mail aliases. (To find out
  34 which databases are supported, try  getent \-\-help .)
  35 Six functions are provided to access the aliases database.
  36 .PP
  37 The
  38 .BR getaliasent ()
  39 function returns a pointer to a structure containing
  40 the group information from the aliases database.
  41 The first time it is called it returns the first entry;
  42 thereafter, it returns successive entries.
  43 .PP
  44 The
  45 .BR setaliasent ()
  46 function rewinds the file pointer to the beginning of the
  47 aliases database.
  48 .PP
  49 The
  50 .BR endaliasent ()
  51 function closes the aliases database.
  52 .PP
  53 .BR getaliasent_r ()
  54 is the reentrant version of the previous function. The requested structure
  55 is stored via the first argument but the programmer needs to fill the other
  56 arguments also. Not providing enough space causes the function to fail.
  57 .PP
  58 The function
  59 .BR getaliasbyname ()
  60 takes the name argument and searches the aliases database. The entry is
  61 returned as a pointer to a struct aliasent.
  62 .PP
  63 .BR getaliasbyname_r ()
  64 is the reentrant version of the previous function. The requested structure
  65 is stored via the second argument but the programmer need to fill the other
  66 arguments also. Not providing enough space causes the function to fail.
  67 .PP
  68 The struct aliasent is defined in <aliases.h>.
  69 .nf
  70 struct aliasent {
  71     char *alias_name;              /* alias name */
  72     size_t alias_members_len;
  73     char **alias_members;          /* alias name list */
  74     int alias_local;
  75 };
  76 .fi
  77 .SH FILES
  78 The default alias database is the file
  79 .IR /etc/aliases .
  80 This can be changed in the
  81 .I /etc/nsswitch.conf
  82 file.
  83 .SH "RETURN VALUE"
  84 The functions
  85 .BR getaliasent_r ()
  86 and
  87 .BR getaliasbyname_r ()
  88 return a non-zero value on error.
  89 .SH EXAMPLE
  90 The following example compiles with
  91 .IR "gcc example.c \-o example" .
  92 It will dump all names in the alias database.
  93 .sp
  94 .nf
  95 #include <aliases.h>
  96 #include <stdio.h>
  97 #include <stdlib.h>
  98 #include <errno.h>
  99
 100 int main() {
 101   struct aliasent *al;
 102   setaliasent();
 103   for (;;) {
 104     al = getaliasent();
 105     if (al == NULL) break;
 106     printf("Name: %s\\n", al->alias_name);
 107   }
 108   if (errno) {
 109       perror("reading alias");
 110       exit(EXIT_FAILURE);
 111   }
 112   endaliasent();
 113   exit(EXIT_SUCCESS);
 114 }
 115 .fi
 116 .SH "CONFORMING TO"
 117 These routines are glibc-specific.
 118 The NeXT has similar routines
 119 .RS
 120 .nf
 121 #include <aliasdb.h>
 122 void alias_setent(void);
 123 void alias_endent(void);
 124 alias_ent *alias_getent(void);
 125 alias_ent *alias_getbyname(char *name);
 126 .fi
 127 .RE
 128 .SH "SEE ALSO"
 129 .BR getgrent (3),
 130 .BR getpwent (3),
 131 .BR getspent (3),
 132 .BR aliases (5)
 133 .\"
 134 .\" /etc/sendmail/aliases
 135 .\" Yellow Pages
 136 .\" newaliases, postalias