pthread question

The following idioms appear a lot in the book "Advanced Programming in
the Unix Environment" by Stevens and Rago

Code:

int err
sigset_t oldmask;
pthread_t tid;

if ((err = pthread_sigmask(SIG_BLOCK, &mask, &oldmask)) ! = 0 )
  err_exit(err, "SIG_BLOCK error");

err = pthread_create(&tid, NULL, thrd_fn, 0);
if(err != 0)
   err_exit(err, "can't create thread");

The question is why don't do something like

Code:

if((err = pthread_create(&tid, NULL, thrd_fn, 0)) != 0)
   err_exit(err, "can't create thread");

like what they do for pthread_sigmask()?

You'd have to ask them about their coding standard
But both are functionally equivalent, so I can't see a reason to be different.

Looks like the book-writers did a copy-and-paste job to put together those examples. You are seeing a mixture of two styles, that's all.