Hello,
char cmd [256];
sprintf (cmd, "gdb attach %d", getpid ());
system (cmd);
'system' waits for the program that it calls to finish.
Thus, your program is waiting for gdb to finish before it
does anything.
Try the appended program which uses raw fork/exec.
It works for me on red hat linux 8, native i686-pc-linux-gnu.
If you try to do this in production code then you are likely
to run into a blizzard of race conditions, error cases,
and signal handling problems. If you are doing this as a learning
experience, that's great -- read up on 'man fork' and
'man execlp', and check out a book on Linux systems programming.