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Framework

Wherever the mail is and whatever format it is stored in, the same operations to manipulate emails are common. To unified the C API, GNU mailutils offers a heteroclite set of objects that work in aggregation to do operations on emails. Each object do a specific task and delegates non related tasks to others. The object comes alive by specifying a URL parameter when created, it will indicate the storage format or protocol (POP3, IMAP4, MH, MAILDIR, etc ..).

                          folder_t                  url_t
  -/var/mail-    +- .. ->+-----------------+   +-->+------------+
 (  alain *-)-+  |       |   url_t       *-|---+   |   port     |
  ----------- |  |       |-----------------|       |   hostname |
 (  jakob *-)-+--+       |   auth_t      *-|---+   |   file     |
  ----------- |          |-----------------|   |   |   ...      |
 (  jeff  *-)-+          |   stream_t      |   |   +------------+
  ----------- |          |-----------------|   |
 (  shaleh*-)-+          |   .....         |   |    auth_t
  ----------             |-----------------|   +-->+------------+
                     +---|-* mailbox_t[]   |       |   ticket_t |
  mailbox_t          |   +-----------------+       +------------+
 +----------------+<-+
 |   locker_t  *--|-------------+
 |----------------|             |
 |   url_t        |             |          locker_t
 |----------------|             +-------->+---------+
 |   stream_t     |                       | lock    |
 |----------------|                       | unlock  |
 |  message_t[] *-|-------+               +---------+
 +----------------+       |                     envelope_t
                          |          +-------->+-----------+
  message_t               |          |         | date      |
 +----------------+<------+          |         | from      |
 |   envelope_t *-|------------------+         | to        |
 |----------------|              header_t      +-----------+
 |   header_t   *-|------------>+--------------+
 |----------------|             |   stream_t   |
 |   body_t     *-|----+        +--------------+
 +----------------+    |    body_t
                       +-->+--------------+
                           |   stream_t   |
                           +--------------+

For example writing a simple from command that will list the From and Subject headers of every mail in a mailbox.

/* sfrom, Simple From */
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <string.h>
#include <mailutils/registrar.h>
#include <mailutils/list.h>
#include <mailutils/mailbox.h>

#define BUFFER_SIZE 64
int
main (int argc, const char **argv)
{
   char from[BUFFER_SIZE];
   char subject[BUFFER_SIZE];
   char *mail;
   mailbox_t mbox;
   int status
   size_t msgno, total = 0;

   mail = (argc == 2) ? argv[1] : getenv ("MAIL");

   /* Register the type of mailbox. IMAP4, POP3 and local format  */
   {
       list_t registrar;
       registrar_get_list (&registrar);
       list_append (registrar, imap_record);
       list_append (registrar, path_record);
       list_append (registrar, pop_record);
   }

   status = mailbox_create (&mbox, mail);
   if (status != 0)
     {
        fprintf (stderr, "mailbox_create: %s\n", strerror (status));
        exit (EXIT_FAILURE);
     }

   status = mailbox_open (mbox, MU_STREAM_READ);
   if (status != 0)
     {
        fprintf (stderr, "mailbox_open: %s\n", strerror (status));
        exit (EXIT_FAILURE);
     }

   mailbox_messages_count (mbox, &total);

   for (msgno = 1; msgno <= total; msgno++)
      {
         message_t msg;
         header_t hdr;

         if ((status = mailbox_get_message (mbox, msgno, &msg)) != 0
             || (status = message_get_header (msg, &hdr)) != 0)
           {
               fprintf (stderr, "Error message:%s\n",
                        strerror (status));
               exit (EXIT_FAILURE);
           }

         status = header_get_value (hdr, MU_HEADER_FROM, from,
                                    sizeof (from), NULL);
         if (status != 0)
            strcpy (from, "(NO FROM)");

         status = header_get_value (hdr, MU_HEADER_SUBJECT, subject,
                                    sizeof (subject), NULL);
         if (status != 0)
            strcpy (subject, "(NO SUBJECT)");

         printf ("%s\t%s\n", from, subject);
      }

    mailbox_close (mbox);
    mailbox_destroy (&mbox);
    return 0;
}

% MAIL=pop://alain@localhost ./sfrom
Passwd: xxxx
Jim Meyering <meyering@foo.org>      fetish(shellutils) beta
Fran@,{c}ois Pinard <pinard@bar.org> recode new alpha
...

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