What are common Linux signals?

Common Linux Signals

In the Linux operating system, signals are a form of inter-process communication (IPC) that allow the kernel or one process to notify another process of an event or condition. Signals are used to handle various types of events, such as errors, interrupts, and user-initiated actions.

Here are some of the most common Linux signals:

SIGINT (Interrupt): This signal is sent when the user interrupts the program, typically by pressing Ctrl+C.
SIGTERM (Terminate): This signal is used to request the termination of a program. It is a polite way of asking a program to shut down.
SIGKILL (Kill): This signal is used to forcibly terminate a program. It cannot be caught, blocked, or ignored by the program.
SIGFPE (Floating-Point Exception): This signal is sent when an arithmetic error occurs, such as division by zero.
SIGSEGV (Segmentation Fault): This signal is sent when a program attempts to access a memory location that it is not allowed to access, such as a null pointer dereference.
SIGPIPE: This signal is sent when a program tries to write to a pipe or socket that has been closed by the other end.
SIGCHLD: This signal is sent to a parent process when one of its child processes terminates or stops.
SIGALRM: This signal is sent when a timer set by the alarm() system call expires.
SIGURG: This signal is sent when urgent data is available on a socket.
SIGUSR1 and SIGUSR2: These are user-defined signals that can be used for custom purposes.

Here's a Mermaid diagram that illustrates the relationships between some of the common Linux signals:

graph TD SIGINT --> Program_Interrupt SIGTERM --> Program_Termination SIGKILL --> Program_Termination SIGFPE --> Arithmetic_Error SIGSEGV --> Memory_Access_Violation SIGPIPE --> Broken_Pipe SIGCHLD --> Child_Process_Event SIGALRM --> Timer_Expiration SIGURG --> Urgent_Data_Available SIGUSR1 --> Custom_Signal_1 SIGUSR2 --> Custom_Signal_2

In this diagram, we can see that signals like SIGINT, SIGTERM, and SIGKILL are related to program interruption and termination, while others like SIGFPE, SIGSEGV, and SIGPIPE are related to specific types of errors or events.

The ability to handle and respond to signals is an important part of writing robust and reliable Linux programs. By understanding the common signals and how they are used, developers can write code that can gracefully handle unexpected events and errors, improving the overall stability and user experience of their applications.