man3/setaliasent.3

   1 .\" Copyright 2003 Walter Harms (walter.harms@informatik.uni-oldenburg.de)
   2 .\"
   3 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   4 .\" Distributed under GPL
   5 .\" %%%LICENSE_END
   6 .\"
   7 .\" Polished a bit, added a little, aeb
   8 .\"
   9 .TH SETALIASENT 3 2015-07-23 "GNU" "Linux Programmer's Manual"
  10 .SH NAME
  11 setaliasent, endaliasent, getaliasent, getaliasent_r,
  12 getaliasbyname, getaliasbyname_r \- read an alias entry
  13 .SH SYNOPSIS
  14 .B #include <aliases.h>
  15 .PP
  16 .B "void setaliasent(void);"
  17 .PP
  18 .B "void endaliasent(void);"
  19 .PP
  20 .B "struct aliasent *getaliasent(void);"
  21 .PP
  22 .BI "int getaliasent_r(struct aliasent *" result ","
  23 .br
  24 .BI "        char *" buffer ", size_t " buflen ", struct aliasent **" res );
  25 .PP
  26 .BI "struct aliasent *getaliasbyname(const char *" name );
  27 .PP
  28 .BI "int getaliasbyname_r(const char *" name ", struct aliasent *" result ,
  29 .br
  30 .BI "        char *" buffer ", size_t " buflen ", struct aliasent **" res );
  31 .SH DESCRIPTION
  32 One of the databases available with the Name Service Switch (NSS)
  33 is the aliases database, that contains mail aliases.
  34 (To find out which databases are supported, try
  35 .IR "getent \-\-help" .)
  36 Six functions are provided to access the aliases database.
  37 .PP
  38 The
  39 .BR getaliasent ()
  40 function returns a pointer to a structure containing
  41 the group information from the aliases database.
  42 The first time it is called it returns the first entry;
  43 thereafter, it returns successive entries.
  44 .PP
  45 The
  46 .BR setaliasent ()
  47 function rewinds the file pointer to the beginning of the
  48 aliases database.
  49 .PP
  50 The
  51 .BR endaliasent ()
  52 function closes the aliases database.
  53 .PP
  54 .BR getaliasent_r ()
  55 is the reentrant version of the previous function.
  56 The requested structure
  57 is stored via the first argument but the programmer needs to fill the other
  58 arguments also.
  59 Not providing enough space causes the function to fail.
  60 .PP
  61 The function
  62 .BR getaliasbyname ()
  63 takes the name argument and searches the aliases database.
  64 The entry is returned as a pointer to a
  65 .IR "struct aliasent" .
  66 .PP
  67 .BR getaliasbyname_r ()
  68 is the reentrant version of the previous function.
  69 The requested structure
  70 is stored via the second argument but the programmer needs to fill the other
  71 arguments also.
  72 Not providing enough space causes the function to fail.
  73 .PP
  74 The
  75 .I "struct aliasent"
  76 is defined in
  77 .IR <aliases.h> :
  78 .PP
  79 .in +4n
  80 .EX
  81 struct aliasent {
  82     char    *alias_name;             /* alias name */
  83     size_t   alias_members_len;
  84     char   **alias_members;          /* alias name list */
  85     int      alias_local;
  86 };
  87 .EE
  88 .in
  89 .SH RETURN VALUE
  90 The functions
  91 .BR getaliasent_r ()
  92 and
  93 .BR getaliasbyname_r ()
  94 return a nonzero value on error.
  95 .SH FILES
  96 The default alias database is the file
  97 .IR /etc/aliases .
  98 This can be changed in the
  99 .I /etc/nsswitch.conf
 100 file.
 101 .SH ATTRIBUTES
 102 For an explanation of the terms used in this section, see
 103 .BR attributes (7).
 104 .ad l
 105 .TS
 106 allbox;
 107 lbw19 lb lb
 108 l l l.
 109 Interface       Attribute       Value
 110 T{
 111 .BR setaliasent (),
 112 .BR endaliasent (),
 113 .BR getaliasent_r (),
 114 .BR getaliasbyname_r ()
 115 T}      Thread safety   MT-Safe locale
 116 T{
 117 .BR getaliasent (),
 118 .BR getaliasbyname ()
 119 T}      Thread safety   MT-Unsafe
 120 .TE
 121 .ad
 122 .SH CONFORMING TO
 123 These routines are glibc-specific.
 124 The NeXT system has similar routines:
 125 .PP
 126 .in +4n
 127 .EX
 128 #include <aliasdb.h>
 129
 130 void alias_setent(void);
 131 void alias_endent(void);
 132 alias_ent *alias_getent(void);
 133 alias_ent *alias_getbyname(char *name);
 134 .EE
 135 .in
 136 .SH EXAMPLE
 137 The following example compiles with
 138 .IR "gcc example.c \-o example" .
 139 It will dump all names in the alias database.
 140 .PP
 141 .EX
 142 #include <aliases.h>
 143 #include <stdio.h>
 144 #include <stdlib.h>
 145 #include <errno.h>
 146
 147 int
 148 main(void)
 149 {
 150     struct aliasent *al;
 151     setaliasent();
 152     for (;;) {
 153         al = getaliasent();
 154         if (al == NULL)
 155             break;
 156         printf("Name: %s\\n", al\->alias_name);
 157     }
 158     if (errno) {
 159         perror("reading alias");
 160         exit(EXIT_FAILURE);
 161     }
 162     endaliasent();
 163     exit(EXIT_SUCCESS);
 164 }
 165 .EE
 166 .SH SEE ALSO
 167 .BR getgrent (3),
 168 .BR getpwent (3),
 169 .BR getspent (3),
 170 .BR aliases (5)
 171 .\"
 172 .\" /etc/sendmail/aliases
 173 .\" Yellow Pages
 174 .\" newaliases, postalias