waitpid()

waitpid - wait for process termination


Headers:
#include 
#include 

DESCRIPTION

The  waitpid  function  suspends  execution of the current
      process until a child as specified by the pid argument has
      exited,  or until a signal is delivered whose action is to
      terminate the current process or to call a signal handling
      function.   If  a  child  as  requested by pid has already
      exited by the time of the call (a so-called "zombie"  pro-
      cess),  the  function  returns  immediately.   Any  system
      resources used by the child are freed.


    The value of pid can be one of:

      < -1   which means to wait for  any  child  process  whose
             process group ID is equal to the absolute value of

      -1     which  means to wait for any child process; this is
             the same behaviour which wait exhibits.

      0      which means to wait for  any  child  process  whose
             process  group  ID  is equal to that of the calling
             process.

      > 0    which means to wait for the child whose process  ID
             is equal to the value of pid.



      The value of options is an exclusive OR of zero or more of
      the following constants:

      WNOHANG which means to return immediately if no child  has
              exited.


      WUNTRACED
              which  means to also return for children which are


     If status is not NULL, wait or waitpid store status infor-
      mation in the location pointed to by statloc.

      This  status  can  be  evaluated with the following macros
      (these macros take the stat buffer as an argument -- not a
      pointer to the buffer!):

      WIFEXITED(status)
              is non -zero if the child exited normally.

      WEXITSTATUS(status)
              evaluates  to  the least significant eight bits of
              the return code of  the  child  which  terminated,
              which  may have been set as the argument to a call
              to exit() or as the argument for a  return  state-
              ment  in the main program.  This macro can only be
              evaluated if WIFEXITED returned non-zero.

      WIFSIGNALED(status)
              returns true if the child process  exited  because
              of a signal which was not caught.

      WTERMSIG(status)
              returns  the  number of the signal that caused the
              child process to terminate. This macro can only be
              evaluated if WIFSIGNALED returned non-zero.

      WIFSTOPPED(status)
              returns true if the child process which caused the
              return is currently stopped; this is only possible
              if the call was done using WUNTRACED.

      WSTOPSIG(status)
              returns  the number of the signal which caused the
              child to stop.  This macro can only  be  evaluated

              if WIFSTOPPED returned non-zero.

              stopped, and whose status has not been reported.