EmbLogic » pid 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 PID, PPID and NICE value of a process https://www.emblogic.com/blog/12/pid-ppid-and-nice-value-of-a-process/ https://www.emblogic.com/blog/12/pid-ppid-and-nice-value-of-a-process/#comments Thu, 31 Dec 2015 08:32:42 +0000 http://www.emblogic.com/blog/?p=13100 Continue reading →]]> PCB (Process Control Board)
———————————-
Every Process has its Process Control Board(PCB) which tells about the process.
PCB contains PID,PPID,PC(program counter),nice value of process.
PID :-
* PID is Process Identification of any process.
* It is a number .
* Every Process has unique PID.
* It generally lies between 2 to 32768.
* 1 is reserved for init process (init starts at system boot & it controls other processeses).
* Obtaining PID of any process getpid() command is used-
#include<sys/types.h>
#include<unistd.h>
pid_t getpid(void);
PPID
* PPID is Parent Process Identification.
* It is also a number.
* Every process has unique PPID.
* It contains the PID of Process which creates this process(Parent Process).
* For Orphan Process PPID is generally 1 (init process).
* Obtaining PID of any process getppid() command is used-
#include<sys/types.h>
#include<unistd.h>
pid_t getppid(void);

NICE value
* OS determines Priority of a process using “nice” value.
* Default nice value is 0.
* Higher the “nice” value of a process, lesser will be  its priority.
* “nice” value of a process (say PROCESS_xyz having PID PID_xyz)can be increased using command -
nice PROCESS_xyz & –> Then it will allocate nice value to be +10.
* We can adjust “nice” value using -
renice 8 PID_xyz  –> It will adjust nice valueof PROCESS_xyz to be +8

]]> https://www.emblogic.com/blog/12/pid-ppid-and-nice-value-of-a-process/feed/ 0