I want use kill() to kill a program. does linux kernel ensure that the program is killed before kill() returned? If not, I have to check whether the program is killed already. Answer does linux kernel ensure that the program is killed before kill() returned? No, kill merely sends a signal to a process or grou…
Tag: signals
Weird Backtrace After a Call Instruction Targeting Signal Functions
I tried to trace evince-3.28.4 execution using GDB. There is a callq instruction at some point in libdl, which is shown below (i.e., at _dl_lookup_symbol_x+840): When the execution reaches here, the backtrace is as follows: But when I enter ni (to jump to the next assembly instruction), it turns into this: As…
Wait for signal from parent and does job and blocks again
Write a program that can display a text string (consisting only of the 26 alphabets and spaces). The program should fork 27 worker processes. Each worker process runs an infinite loop in which it waits for a signal from the controller (i.e., parent), sleeps for 1 sec, prints its pre-defined character, signals…
Setting signal for SIGWINCH causes output on terminal?
When I set up a signal handler for SIGWINCH that does nothing, resizing the terminal window causes a reverse ? character to show up, get several of them as I resize the window around. If I don’t setup a signal handler, that doesn’t happen. Why is it doing that and How do I stop that? More informat…
How to trap CTRL+Z in Linux POSIX shell script; possible or not?
I am a Linux shell scripter, I would like to know if it is possible to trap signal for script sleep: That is Ctrl+z? I do it at the moment like this and would like to trap that sleep signal too. Where the print_error_and_exit function just does as its name says. Goal: I would like to ignore this signal, if
How to gracefully shutdown a Go service running on Kubernetes
I have an API written in Go that has been Dockerised and runs in a Kubernetes cluster on GKE. At the moment my API server does not handle any shutdown scenarios such as a Pod dying or being purposefully brought down. What set of UNIX signals should I expect to trap to gracefully shutdown the server and what c…
Kill all processes from C in Linux
I am writing a Linux C program that will be executed as init. It will eventually need to shut down the system. I have code for unmounting all the filesystems and actually turning off the system; now I just need a way for it to send SIGTERM to all processes, sleep(5), then send SIGKILL to any remaining process…
What are the relation and difference between a signal mask and a signal set?
From APUE Each process has a signal mask that defines the set of signals currently blocked from delivery to that process. We can think of this mask as having one bit for each possible signal. If the bit is on for a given signal, that signal is currently blocked. A process can examine and change its current sig…
Signal all processes in process group except self
I am writing a program which multiple processes will run concurrently. In this program, there is a need for one process to suspend all other participants temporarily. In order to spare myself the overhead of tabulating all participant process ID’s in a shared page and signaling them individually, I have…
Signal Handler Behavior
I have just some questions about the system calls signal, kill and the signal handler. I have this code: 1) I don’t understand why the first printf in the first child, return -1 without a sleep(1) before…seems that the handler is executed after the beginning of the child. 2) When there is a kill t…