the process from outside like any other signal. , and "Signal alarm", "signal VT alarm", "signal profiling timer alarm" The SIGALRM, SIGVTALRM and SIGPROF signal is sent to a process when the time limit specified in a call to a preceding alarm setting function (such as setitimer) elapses. SIGALRM is sent when real or clock time elapses. SIGVTALRM is sent when CPU time used by the process elapses. SIGPROF is sent when CPU time used by the process and by the system on behalf of the process elapses, i.e. when the profiling timer expires. "Signal bus" The SIGBUS signal is sent to a process when it causes a bus error. The conditions that lead to the signal being sent are, for example, incorrect memory access alignment or non-existent physical address. "Signal child" The SIGCHLD signal is sent to a process when a child process terminates, is interrupted, or resumes after being interrupted. One common usage of the signal is to instruct the operating system to clean up the resources used by a child process after its termination without an explicit call to the wait system call. "Signal continue" The SIGCONT signal instructs the operating system to continue (restart) a process previously paused by the SIGSTOP or SIGTSTP signal. One important use of this signal is in job control in the Unix shell. "Signal floating-point error" The SIGFPE signal is sent to a process when an exceptional (but not necessarily erroneous) condition has been detected in the floating point or integer arithmetic hardware. This may include division by zero, floating point underflow or overflow, integer overflow, an invalid operation or an inexact computation. Behaviour may differ depending on hardware. "Signal hangup" The SIGHUP signal is sent to a process when its controlling terminal is closed. It was originally designed to notify the process of a serial line drop (a hangup). In modern systems, this signal usually means that the controlling pseudo or virtual terminal has been closed. Many daemons (who have no controlling terminal) interpret receipt of this signal as a request to reload their configuration files and flush/reopen their logfiles instead of exiting. nohup is a command to make a command ignore the signal. "Signal illegal" The SIGILL signal is sent to a process when it attempts to execute an illegal, malformed, unknown, or privileged instruction. "Signal interrupt" The SIGINT signal is sent to a process by its controlling terminal