Unix - Signals and Traps

In Unix, signals and traps are two mechanisms used to handle and respond to certain events or conditions that occur during the execution of a program or a shell script.

Signals are software interrupts that are sent to a process to notify it of an event. Signals can be sent by the kernel or by another process, and can be used to notify a process of events such as errors, user interrupts, or the termination of a child process. When a process receives a signal, it can handle it by performing a specific action or terminating the process. Some common signals in Unix include SIGINT (sent by the user when they press Ctrl-C), SIGTERM (sent to request a process to terminate), and SIGKILL (sent to forcibly terminate a process).

Traps, on the other hand, are a mechanism used in shell scripts to respond to certain events, such as errors or interrupts. A trap is a command or a set of commands that is executed when a specified signal is received by the shell script. For example, a trap could be set to execute a cleanup function when a script receives a SIGINT signal, allowing the script to clean up any resources before terminating.

Both signals and traps are important mechanisms for handling events and errors in Unix. By responding to signals and setting traps in shell scripts, developers and system administrators can ensure that their programs and scripts are able to handle unexpected events and errors gracefully, improving the reliability and stability of their Unix systems.