Author: Mark Wielaard <mjw@redhat.com>

getbuildid.c

/* Requires elfutils-devel >= 0.159
   gcc -g -O2 -Wall -lelf -ldw -o getbuildid getbuildid.c */

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <libelf.h>
#include <elfutils/libdwelf.h>

int
main (int argc, char **argv)
{
  int c, rc = 0;
  elf_version (EV_CURRENT);
  for (c = 1; c < argc; c++)
    {
      int fd = open (argv[c], O_RDONLY);
      if (fd >= 0)
	{
	  Elf *elf = elf_begin (fd, ELF_C_READ, NULL);
	  if (elf != NULL)
	    {
	      if (elf_kind(elf) == ELF_K_ELF)
		{
		  const void *build_id;
		  ssize_t len = dwelf_elf_gnu_build_id (elf, &build_id);
		  if (len < 0)
		    {
		      fprintf (stderr, "error getting buildid for '%s': %s\n",
			       argv[c], elf_errmsg (-1));
		      rc = 1;
		    }
		  else if (len == 0)
		    {
		      fprintf (stderr, "'%s' has no build-id\n", argv[c]);
		      rc = 1;
		    }
		  else
		    {
		      const unsigned char *p = build_id;
		      const unsigned char *end = p + len;
		      printf ("%s: ", argv[c]);
		      while (p < end)
			printf ("%02x", (unsigned)*p++);
		      printf ("\n");
		    }
		}
	      else
		{
		  fprintf(stderr, "Not an ELF file '%s'\n", argv[c]);
		  rc = 1;
		}
	      elf_end (elf);
	    }
	  else
	    {
	      fprintf(stderr, "Couldn't create ELF for '%s': %s\n",
		      argv[c], elf_errmsg (-1));
	      rc = 1;
	    }
	  close (fd);
	}
      else
	{
	  fprintf(stderr, "Couldn't open '%s': %m\n", argv[c]);
	  rc = 1;
	}
    }

  return rc;
}