Use a conditional breakpoint that checks the first parameter. On 64-bit x86 systems the condition would be:
(gdb) b write if 1==$rdi
On 32-bit systems, it is more complex because the parameter is on the stack, meaning that you need to cast $esp to an int * and index the fd parameter. The stack at that point has the return address, the length, buffer and finally fd.
This varies greatly between hardware platforms.