problem with gcc linker

[tap3ah]

hi
I'm trying to compile an example from Stevens' apue book.

#include "apue.h"
#include <dirent.h>

int main(int argc,char *argv[]){
  DIR *dp;
  struct dirent *dirp;
  if(argc!=2)
    err_quit("usage: ls directory_name");
  if((dp=opendir(argv[1]))==NULL)
    err_sys("can't open %s",argv[1]);
  while((dirp=readdir(dp))!=NULL)
    printf("%s\n",dirp->d_name);
  closedir(dp);
  exit(0);
}

include/apue.h contains declarations of err_quit and err_sys and lib/error.c their definitions. The library is successfully compiled into lib/error.o and main program into ls1.o.
When I run
gcc ls1.o lib/error.o -o ls1
or
gcc lib/error.c ls1.c -Iinclude -o ls1
it compiles fine, but
gcc -Llib/ -Iinclude ls1.c -o ls1
generates

/tmp/ccfva0gO.o: In function `main':
ls1.c:(.text+0x20): undefined reference to `err_quit'
ls1.c:(.text+0x5b): undefined reference to `err_sys'
collect2: ld returned 1 exit status

It looks like gcc ignores -L switch.
Am I doing something wrong?
I'm using gcc version 4.5.0 20100604 [gcc-4_5-branch revision 160292] (SUSE Linux) on openSUSE 11.3.
Thanks in advance

[jsmith]

-L tells the compiler where to find libraries at link time.

lib/error.o is not a library -- it is an object file.

Your first two work because you are telling the compiler to compile and link ls1.c and lib/error.c into
the executable.

The last one says compile and link ls1.c into an executable, searching lib/ for any libraries (.a or .so)
that you need.

[tap3ah]

OK, I figured it out. There are 2 things I misunderstood about -L switch.
* -L is not enough, -l has to be used to specify which file to link. I wrongly assumed linker will search the directory for needed definitions.
* an object file can't be linked directly, it has to be part of the archive.
So, it would be:
ar rcs lib/liberror.a lib/error.o
followed by
gcc ls1.o -o ls1 -Llib/ -lerror
or
gcc ls1.c -Iinclude/ -o ls1 -Llib/ -lerror
The irony is that I didn't notice that make already created lib/libapue.a with all object files. All I had to do is link it. Live and learn.
jsmith, thank you for the response
cheers