How to develop simple dcap clients tools using libdcap with C

1. Get yourself a copy of the dcap source code by either checking out complete dCache or just the submodule dcap.

• on the command line: svn co  svn+ssh://svn.dcache.org/store/dCache/trunk/modules/dcap
• or browse the dcap code  online

In case you checked out, build the library simply by typing make.

2. Important files

• libdcap.so (the binary of the dcap client lib, either built by you through the previous make or shipped with the dcache-server-rpm under /opt/d-cache/dcap/lib)
• dcap.h (main interface to dcap, either part of the dcap source or shipped with the dcache-server-rpm under /opt/d-cache/dcap/include/)
• dcap_test.c (good example, start here to look how to use libdcap)

3. How to compile you app, linked against libdcap

gcc -D_GNU_SOURCE -I/opt/d-cache/dcap/include/ -L/opt/d-cache/dcap/lib -ldcap -o /tmp/dc_exists /tmp/dc_exists.c 

4. A simple example how to check whether a file exists (dcap stat)

#include <dcap.h>
#include <stdio.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{

   if( argc != 2 ) {
      printf("usage: %s <filename>
", argv[0]);
      exit(1);
   }

   dc_setDebugLevel(0);

   return dc_access(argv[1], F_OK);

}