Sending signals to other processes

After seeing the way in which incoming signals are handled, let's take a look at how to send signals to other processes programmatically. The os.Process structure is the only tool we need—its Signal method makes it possible to send a signal to the project. It's that easy!

The less simple part is obtaining the process. There are two use cases, as follows:

• The process is a child, and we have the process value already as a result of os.StartProcess or exec.Command structs.
• The process is already existing but we do not have it, so we need to search for it using its PID.

The first use case is simpler, as we already have the process as a variable, or as an attribute of an exec.Cmd variable, and we can call the method directly.

The other use case requires searching for the process by PID using the os.FindProcess method, as follows:

p, err := os.FindProcess(pid)
if err != nil {
    panic(err)
}

Once we have os.Process, we can use its Signal method to send a specific signal to it, as follows:

if err = p.Signal(syscall.SIGTERM); err != nil {
    panic(err)
}

The type of signal we will send to a process depends on the destination process and the behavior we want to suggest, such as an interruption or a termination.