exit

I am a noob in shell-scripting. I want to print a message and exit my script if a command fails. I've tried: my_command && (echo 'my_command failed; exit) but it does not work. It keeps executing the instructions following this line in the script. I'm using Ubuntu and bash. Try: my_command || { echo 'my_command failed' ; exit 1; } Four changes: Change && to || Use { } in place of ( ) Introduce ; after exit and spaces after { and before } Since you want to print the message and exit only when the command fails ( exits with non-zero value) you need a || not an && . cmd1 && cmd2 will run cmd2

I was really confused by sys.exit() in python. In python documentation , it says "Exit from Python"; does that mean when sys.exit() is called in a python program, the process will exit? If so, the code below shows a different result: import sys import time import threading def threadrun(): while(True): time.sleep(1) if __name__=="__main__": t=threading.Thread(target=threadrun) t.start() sys.exit() Launching this program in linux, result was not the expected one as python documentation says but still run in the system, so what does sys.exit() really do? As per the documentation sys.exit()

Let's say I have the following code: struct mytype { ~mytype() { /* do something like call Mix_CloseAudio etc */ } }; int main() { mytype instant; init_stuff(); start(); return 0; } Is that destructor guaranteed to be called even if exit() is used from somewhere inside start() ? If you call exit , the destructor will not be called. From the C++ standard (§3.6.1/4): Calling the function void exit(int); declared in <cstdlib> (18.3) terminates the program without leaving the current block and hence without destroying any objects with automatic storage duration (12.4). If exit is called to end a

I've been trying to figure out how the fork-exec mechanism is used inside Linux. Everything was going on according to the plan until some web pages started to confuse me. It is said that a child process should strictly use _exit() instead of a simple exit() or a normal return from main() . As I know, Linux shell fork-execs every one of the external commands; assuming what I said above is true, the conclusion is that none of these external commands nor any other execution happening inside the Linux shell can do normal return! Wikipedia & some other webpages claim we've got to use _exit() just