SIGCONT

SIGCONT is a signal defined by the POSIX standard for Unix-like systems. It is used to resume a process that has been stopped by a job-control signal such as SIGSTOP, SIGTSTP, SIGTTIN, or SIGTTOU. The default action of SIGCONT is to continue the process’s execution. If the process is already running, the signal typically has no effect. A process may install a handler for SIGCONT or ignore the signal; if a handler is present, it will run upon receipt, and if the signal is ignored, the process still resumes execution because the primary effect of the signal is to continue.

SIGCONT can be delivered to a single process or to an entire process group. It is commonly sent using the kill system call with the SIGCONT action, and shells or job-control utilities may target a process group to resume all related processes.

In the context of job control, SIGCONT is used to resume stopped jobs. When a user suspends a job (for example, with Ctrl-Z) and later restores it (with the foreground or background commands), the controlling shell sends SIGCONT to the relevant process or process group. If a job is resumed in the foreground, terminal control is typically reassigned to that job; background resumes continue without taking terminal control, subject to the shell’s job-control policies.

Related signals include SIGSTOP, SIGTSTP, SIGTTIN, and SIGTTOU, which are associated with stopping processes or related terminal conditions. SIGCONT is one of the core mechanisms enabling Unix-like systems to manage and resume processes within a multi-process environment.