![]() Also if the program has truly crashed it may not respond to the instruction so use the -9 option in that case. Remember that the kill argument is non-interactive (it doesn't ask for confirmation before starting) and non-verbose (it doesn't tell you what it is doing) by default and hence must be used carefully. In case you want to terminate a process that you started, you can do so from a terminal using the kill command. The system also runs a lot of its own processes in the background. On a graphical desktop, that command doesn't show the programs you start from menus or by clicking on icons. In fact, it shows only the processes you started from the terminal in which you issue the command. Now, you may well expect that your machine has a lot more processes than the ones you see by running a simple ps without arguments. You can use the tty command to find out which terminal you are presently in. The second column in the output of ps specifies the terminal to which the process is attached or the terminal that controls the process. ![]() The gap between the PID 3923 for sh and the PID 3941 for cat merely shows that somebody started processes on the machine in between the times these two processes started. This is an integer number that is given to each new process, and is called the PID (for "process ID"). The 4 columns have the following interpretation: Process ID Terminal CPU Time Program/CommandĮach process has an identifier by which the operating system tracks it. Here we find there are 4 processes that we are running from our terminal. The ps command, when you run it without any arguments, displays processes run by the current user. We can use the ps and top commands to view processes running on our machine. For example, the nano editor responds to it by displaying the current position in the file being edited. Some programs catch SIGINT and use it for a specific purpose. If that process has not set up a response to SIGINT (we say it catches SIGINT), then it will be terminated immediately with possible loss of data (but open files do get closed). It is delivered to the process that is in the foreground in the currently active terminal. ![]() The SIGINT signal is raised when the user presses the key combination. Interrupting (CTRL-C)The kernel delivers signals to processes for many reasons. Each and every program we run is a process. ![]() Programs in binary/executable form reside on your disk when they are executed (run), they are moved into memory and become a process. ![]()
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