WCONTINUED

WCONTINUED is a status option used with the wait and waitpid system calls in POSIX-compliant Unix-like systems. It indicates that a child process has been continued after being stopped, typically by the delivery of the SIGCONT signal or after a job-control resume. WCONTINUED is supplied as a bit flag in the options argument to wait or waitpid to request notification when a previously stopped process is continued.

When WCONTINUED is used, a state change that includes a continued state may be reported by the waithouse call. The status value returned by wait or waitpid can be examined with macros such as WIFCONTINUED(status), which evaluates to true if the child has been continued. This continued state is distinct from other state changes reported by the macros WIFEXITED, WIFSIGNALED, and WIFSTOPPED. After a process is continued, it runs until its next state change or termination, just as with any other execution state transition.

Portability and usage notes: WCONTINUED is defined in the POSIX wait interface (for example, POSIX.1-2001 and later). It is available on common Unix-like platforms such as Linux, macOS, and BSD variants. Programs should include the appropriate headers, typically sys/wait.h, and may combine WCONTINUED with other options (for example, WNOHANG) in the waitpid call. In practice, WCONTINUED helps distinguishing resumed processes from those that have exited, been signaled, or stopped, contributing to robust process control in multi-process applications.