SIGSEGV is the symbolic name for the signal thrown by computer programs making invalid memory references on POSIX compliant platforms. SIGSEGV is a symbolic constant defined in signal.h, the name is a contraction of Segmentation Violation, SIG is a common prefix for signal names.

Symbolic signal names are used as signal numbers can vary across platforms.

Computer programs may throw SIGSEGV for improper memory handling (for further discussion, see segmentation fault). The operating system may inform the application of the nature of the error using the signal stack , which developers can use to debug their programs or handle errors.

The default action on being sent SIGSEGV is an abnormal termination, this will end the process but may generate a core file to aid debugging, or other platform dependent action. For example, Linux systems using the grsecurity patch may log SIGSEGV signals in order to monitor for possible intrusion attempts using buffer overflows.

SIGSEGV can be handled (caught), that is, applications can request what action they want to occur. Examples of such action might be ignoring it, calling a function, or restoring the default action. In some circumstances, ignoring SIGSEGV can result in undefined behaviour.

An example of an application that might handle SIGSEGV is a debugger, which might check the signal stack and inform the developer of what happened, and where his program terminated.

SIGSEGV is usually generated by the Operating System, however users with appropriate permissions can use the kill() system call, or kill command (userland program, or sometimes a shell builtin) to send the signal to a process at will.