This loop uses headerNextIterator() to return each entry's tag, type, data, and size. By using a switch statement on the tag, we can perform different operations on each type of entry in the header:

while (headerNextIterator(iter, &itertag, &type, p, &count)) {

  switch (itertag) {

 case RPMTAG_SUMMARY:

    blather = *p;

      printf("The Summary: %s\n", blather);

    break;

  case RPMTAG_FILENAMES:

        printf("There are %d files in this package\n", count);

     break;

 }

This is the housecleaning section of the program. First we free the iterator that we've been using, and finally the header itself:

}



headerFreeIterator(iter);



headerFree(h);



}

Running this program on a package gives us the following output:

# ./dump amanda-client-2.3.0-2.i386.rpm

There is a postinstall script for amanda-client

Dumping signatures...

Entry count: 2

Data count : 20



             CT  TAG                 TYPE           OFSET      COUNT

Entry      : 000 (1000)NAME          INT32_TYPE    0x00000000 00000001

       Data: 000 0x00029f5d (171869)

Entry      : 001 (1003)SERIAL        BIN_TYPE      0x00000004 00000016

       Data: 000 27 01 f9 97 d8 2c 36 40

       Data: 008 c6 4a 91 45 32 13 d1 62

Iterating through the header...

The Summary: Client-side Amanda package

There are 11 files in this package

#

21.3.2. Example #2

This example delves a bit more into the database-related side of rpmlib. After initializing rpmlib's variables by reading the appropriate rpmrc files, the code traverses the database records, looking for a specific package. That package's header is then dumped in its entirety.

As before, this is the normal way of including all of rpmlib's definitions:

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <stdlib.h>



#include <rpm/rpmlib.h>

Here are the data declarations. Note the declaration of db; this is how we will be accessing the RPM database:

void main(int argc, char ** argv)

{

Header h;

int offset;

int dspBlockNum = 0;                      /* default to all */

int blockNum = 0;

int_32 type, count;

char * name;

rpmdb db;

Before opening the RPM database, it's necessary to know where the database resides. This information is stored in rpmrc files, which are read by rpmReadConfigFiles(). To show that this function is really doing its job, we retrieve the RPM database path before and after the rpmrc files are read. Note that we test the return value of rpmGetVar(RPM_DBPATH) and, if it is null, we insert (none) in the printf() output. This prevents possible core dumps if no database path has been set; and besides, it's more user friendly:

printf("The database path is: %s\n",

    rpmGetVar(RPMVAR_DBPATH) ? rpmGetVar(RPM_DBPATH) : "(none)");



rpmReadConfigFiles(NULL, NULL, NULL, 0);



printf("The database path is: %s\n",

    rpmGetVar(RPMVAR_DBPATH) ? rpmGetVar(RPM_DBPATH) : "(none)");

Here we're opening the RPM database and doing some cursory error checking to make sure we should continue:

if (rpmdbOpen("", &db, O_RDONLY, 0644) != 0) {

           fprintf(stderr, "cannot open /var/lib/rpm/packages.rpm\n");

      exit(1);

}

We get the offset of the first database record:

offset = rpmdbFirstRecNum(db);

Here we start a while loop based on the record offset. As long as there is a non-zero offset (meaning that there is still an available record), we get the record. If there's a problem getting the record, we exit:

while (offset) {



    h = rpmdbGetRecord(db, offset);

    if (!h) {

            fprintf(stderr, "headerRead failed\n");

    exit(1);

            }

Next, we get the package name entry from the record and compare it with the name of the package we're interested in. If it matches, we dump the contents of the entire record:

headerGetEntry(h, RPMTAG_NAME, &type, (void **) &name, &count);

if (strcmp(name, argv[1]) == 0)

  headerDump(h, stdout, 1);

At the end of the loop, we free the record and get the offset to the next record:

headerFree(h);



offset = rpmdbNextRecNum(db, offset);

}

At the end, we close the database and exit:

rpmdbClose(db);

}

Here's the program's output, edited for brevity (notice that the database path changes from (null) to /var/lib/rpm after the rpmrc files are read):

# ./showdb amanda-client

The database path is: (null)

The database path is: /var/lib/rpm

Entry count: 37

Data count : 5219



             CT  TAG                  TYPE                OFSET      COUNT

Entry      : 000 (1000)NAME        STRING_TYPE        0x00000000 00000001

        Data: 000 amanda-client

Entry      : 001 (1001)VERSION     STRING_TYPE        0x0000000e 00000001

       Data: 000 2.3.0

Entry      : 002 (1002)RELEASE     STRING_TYPE        0x00000014 00000001

      Data: 000 7

Entry      : 003 (1004)SUMMARY     STRING_TYPE        0x00000016 00000001

        Data: 000 Client-side Amanda package

Entry      : 004 (1005)DESCRIPTION STRING_TYPE        0x00000031 00000001

...

Entry      : 017 (1027)FILENAMES   STRING_ARRAY_TYPE 0x00000df3 00000015

       Data: 000 /usr/doc/amanda-client-2.3.0-7

       Data: 001 /usr/doc/amanda-client-2.3.0-7/COPYRIGHT

        Data: 002 /usr/doc/amanda-client-2.3.0-7/INSTALL

       Data: 003 /usr/doc/amanda-client-2.3.0-7/README

       Data: 004 /usr/doc/amanda-client-2.3.0-7/SYSTEM.NOTES

       Data: 005 /usr/doc/amanda-client-2.3.0-7/WHATS.NEW

        Data: 006 /usr/doc/amanda-client-2.3.0-7/amanda-client.README

...

Entry      : 034 (1049)REQUIRENAME STRING_ARRAY_TYPE 0x0000141c 00000006

       Data: 000 libc.so.5

       Data: 001 libdb.so.2

      Data: 002 grep

      Data: 003 sed

       Data: 004 NetKit-B

       Data: 005 dump

...

#

As you can see, everything that you could possibly want to know about an installed package is available using this method.

21.3.3. Example #3

This example is similar in function to the previous one, except that it uses rpmlib's search functions to find the desired package record. Here we include rpmlib's definitions:

#include <errno.h>

#include <fcntl.h>

#include <stdio.h>

#include <string.h>

#include <unistd.h>

#include <stdlib.h>



#include <rpm/rpmlib.h>

Here are the storage declarations:

void main(int argc, char ** argv)

{

    Header h;

     int stat;

    rpmdb db;

      dbiIndexSet matches;

In this section, we do some argument processing, process the rpmrc files, and open the RPM database:

if (argc != 2) {

      fprintf(stderr, "showdb2 <search term>\n");

    exit(1);

}



rpmReadConfigFiles(NULL, NULL, NULL, 0);



if (rpmdbOpen("", &db, O_RDONLY, 0644) != 0) {

           fprintf(stderr, "cannot open /var/lib/rpm/packages.rpm\n");

      exit(1);

}

In this section, we use rpmdbFindPackage() to search for the desired package:

stat = rpmdbFindPackage(db, argv[1], &matches);

printf("Status is: %d\n", stat);

if (stat == 0) {

    if (matches.count) {

        printf("Number of matches: %d\n", matches.count);

        h = rpmdbGetRecord(db, matches.recs[0].recOffset);

        if (h) headerDump(h, stdout, 1);

        headerFree(h);

          dbiFreeIndexRecord(matches);

  }

}