Signal Handling--ref

Thepausefunction is declared in`unistd.h'.

pause

pausecan conceal serious timing errors that can make a program hang mysteriously.

pauseif the real work of your program is done by the signal handlers themselves,and the "main program" does nothing but callpause. Each time a signal is delivered,the handler will do the next batch of work that is to be done,and then return,so that the main loop of the program can callpauseagain.

pauseto wait until one more signal arrives,and then resume real work. Even if you arrange for the signal handler to cooperate by setting a flag,you still can't usepausereliably. Here is an example of this problem:

/* usr_interrupt is set by the signal handler.  */
if (!usr_interrupt)
  pause ();
/ Do work once the signal arrives.  /

...

usr_interruptis checked,but before the call topause. If no further signals arrive,the process would never wake up again.

sleepin a loop,instead of usingpause. (See section,for more aboutsleep.) Here is what this looks like:

/* usr_interrupt is set by the signal handler.
while (!usr_interrupt)
  sleep (1);
                        
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