FreeBSD 7.0 manual page repository

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alarm - set signal timer alarm



      alarm - set signal timer alarm


      Standard C Library (libc, -lc)


      #include <unistd.h>
      unsigned int
      alarm(unsigned int seconds);


      This interface is made obsolete by setitimer(2).
      The alarm() function sets a timer to deliver the signal SIGALRM to the
      calling process after the specified number of seconds.  If an alarm has
      already been set with alarm() but has not been delivered, another call to
      alarm() will supersede the prior call.  The request alarm(0) voids the
      current alarm and the signal SIGALRM will not be delivered.
      Due to setitimer(2) restriction the maximum number of seconds allowed is
      The return value of alarm() is the amount of time left on the timer from
      a previous call to alarm().  If no alarm is currently set, the return
      value is 0.
      setitimer(2), sigaction(2), sigpause(2), sigvec(2), signal(3), sleep(3),
      ualarm(3), usleep(3)


      An alarm() function appeared in Version 7 AT&T UNIX.


Based on BSD UNIX
FreeBSD is an advanced operating system for x86 compatible (including Pentium and Athlon), amd64 compatible (including Opteron, Athlon64, and EM64T), UltraSPARC, IA-64, PC-98 and ARM architectures. It is derived from BSD, the version of UNIX developed at the University of California, Berkeley. It is developed and maintained by a large team of individuals. Additional platforms are in various stages of development.