EmbLogic » linux system programming https://www.emblogic.com/blog Embedded System and ARM Training Tue, 03 Mar 2020 13:00:06 +0000 en-US hourly 1 http://wordpress.org/?v=3.9.1 How to Send a signal -Using Kill command https://www.emblogic.com/blog/01/how-to-send-a-signal-using-kill-command/ https://www.emblogic.com/blog/01/how-to-send-a-signal-using-kill-command/#comments Fri, 15 Jan 2016 12:01:08 +0000 http://www.emblogic.com/blog/?p=13175 Continue reading →]]> Send a signal by Kill command
=======================
- To send a signal to a process other than current task.
- It has prototype :-
int kill(pid_t pid, int signo);
- It is included using header :-
#include<signal.h>
- The system data type pid_t is defined in header :-
#include<sys/types.h>
- signo is the signal number of signal to be send.
- pid is the PID of the process to which signal is to be send.
- pid can take value:-
* 0 –> To send signo signal to every process in invoking process’ process group
* -1 –>To send signo signal to every process for which invoking process has permission to send a signal, except itself and init
* n(<-1) –> All process in process group
* n(>0)  –> process with PID n is signalled.
- This take an optional signal name or number and the PID to send the signal.

- For eg. To send ‘hangup’ signal to shell running on PID 1001, we use command :-
kill(1001,HUP);
- killall is used to send signal to all the processes running.

]]> https://www.emblogic.com/blog/01/how-to-send-a-signal-using-kill-command/feed/ 0 How to register a signal https://www.emblogic.com/blog/01/how-to-register-a-signal/ https://www.emblogic.com/blog/01/how-to-register-a-signal/#comments Fri, 15 Jan 2016 11:59:04 +0000 http://www.emblogic.com/blog/?p=13173 Continue reading →]]> Register a signal
==================
- Program can handle a signal using signal library function signal().
- signal() is used to register the signal handler function with kernel on behalf of current process.
- It is included in header :-
#include<header.h>
- Prototype of function is :-
void* (signal(int signo,void(*func)(int)))(int);
- signal() function takes 2 parameters, signo and func.
- The signal to be caught or ignored is given as argument signo.
- The function to be called when the specified signal is received is given as func.
- The function must take a single int argument (the signal received) and has return type void.

- The signal() command can be used in 3 modes :-
(i) Default mode (Terminate the process)
SIG_DFL –> is used in place of func.
(ii) Ignore the signal
SIG_IGN –> is used in place of func.
(iii) User defined mode
User defined function is used in place of func.

- The signal command returns the function which is setup to handle the signal, SIG_DFL or SIG_IGN in 3rd, 1st and 2nd cases respectively.

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