Linux - Traps and signals

now in this video we are going to talk

about the traps and signals by name

itself traps perhaps means we are going

to stuck somewhere so if you are going

to stuck somewhere what you are going to

do and signals can be any kind of signal

it can be your user requests it can be

any termination signal it can be a

failure signal signals are nothing but

any particular event your Linux

operating system gets or any other

operating system gets so if any event

triggers or if any event happens what

your system does that we are going to

see here very first what are the signals

signals are any software interrupts

which are sent to the program to

indicate that the important event has

occurred signals are the software

interrupts send to a particular program

to indicate that the important event has

occurred now this event is not only the

interrupt interrupt means you are going

to you know just your system or a

particular user to get particular tasks

to be stopped and perform your task it

can be any kind of interrupt interrupts

have many type it has a request

interrupt like we are requesting our

resources so to stop your work and give

our pro service two priorities or our

services or priorities like we have said

the priorities into the nice values so

those are the interrupts again if I'm

creating offer if I'm asking my system

to save the file it is again an

interrupt if I do not want a particular

applications to be performed

applications to be used I can close

those particular application that is

again an interrupt I'm asking my

resources to close an application so

whatever we are going to do whatever the

task will perform it your system take it

as an interrupt so it is a software

signals which is your user is performing

either your system also sometimes gives

you some kind of interrupts now the

events or we can say what are the

interrupts triggers these already is

requested illegally by the users or your

illegal memory access errors it might

happen sometimes your memory is less you

don't have the insufficient amount of

RAM for performing any particular task

so your system will trigger an event

that your memory is slow or your memory

is not sufficient that is insufficient

memory access

so all this events will be provided by

the system so they are again of events

or they are again of signals some

signals such as interrupt signals which

we have can indicate that the user has

asked something to be denied or

something to be canceled those

particular signals can also be used

which shows that particular system that

this is not a flow which we are going to

use so sometimes you are using a

particular process the process and

services are running and suddenly you

close that behavior service or you stop

that service means we are not in the

usual flow the system has requested

something which is not into the flow so

this again signals are called as the

interrupt signals so let us see which

are the type of signals we have into our

systems and when we give any kind of

interrupts which type of signals we have

so their signals are in such a way so

these are the abbreviation of your

signals sign up and signal int and

signal quit signal FPE

signal kill signal alarm and signal

terminate so these are the signals we

have and they are also associated with

the numbers which is used by your Linux

operating system to understand the

signals like for sick up we have one

which hang up the dedicated or it

detects any particular hang-up or traps

into a particular process now for

example you might experience you have

logged into a terminal and you have run

some service but a service is not again

started and even you are not getting the

prompt or any particular error so you

are completely hung over there so that

time if you want that this particular

signals are getting hung and if you want

to check what signals your system is

getting so by default it gets a signal

that is signal 1 which controls those

particular signal or we can say it will

directly get the controlling process

completely which is controlling the

signal

that signal is called as a sick huh sing

it now second again is an interrupt

provided by the user for stopping

certain process by pressing ctrl + C so

what happens if suppose I'm starting

with some process for example I can take

I'm pinging a particular host if I'm

giving the command ping and the host

name or a host IP address it

continuously go on pinging it now if I

want to stop the communication I can

press control C so when I press control

C it will by default take the signal cut

a signal interrupt that is 2 then we

have SiC quit SiC quit is when a user

want to quit out of the terminal either

we come give the command exit or either

we give control D so that time the

signal which is positive to our system

is signal 3 or we call it as SiC quit

signal again FPE it is the prog in

mathematical operation error where if

suppose I have used some invalid

operators like in spite of addition I

have you something else which we

generally do not use like if I have used

at the rate sign so it's not any kind of

automatically operator so that time it

will be giving me an error this error

signals will be either 8 while sticking

into the input and it tooks called as

sick FBE airs same sick kill sick kill

is again a particular process which

terminates a particular service by

killing the particular service

completely but it doesn't clean up the

complete free now for example I have

started Firefox twice and one of my

Firefox is not working one of my browser

is not working we do to any particular

error so if I stop only that browser so

it will kill the process but it won't

kill complete tremens other than that if

other fire first process are running it

won't clean up those things that is your

say kill so it kills a particular

process then we have sick alarm sig Alam

is the clock alarms provided by some of

the signals now for example I have

scheduled to my system shutdown after

one hour so before 1:00 our if will

alarm me that my system is going to shut

down because I

scheduled something now for example and

my system is going to be backed up after

one week so it will give me our alarm

the alarm is set on this particular date

on this particular system so those are

the signal alarms which it prompts us

while we have already scheduled

something the next we have that is sick

da minute so if suppose we are running

some software's

or if you are running some services I

want to completely kill the tree or if I

can terminate the whole process along

with the tree of this process we can go

for sick jump which input it takes as -

15 so if suppose you are trapped

somewhere or if suppose you are not able

to you move out of a particular console

you can move into other terminal and you

can give any of the signals whichever

you would require from the other

terminals as well so but while defining

or managing the signals we have to give

the command called as kill kill is what

killing the signals and this signals can

be used so which kind of termination of

process do you require so you need to

specify in such a way kill space and

then the signal name with - so once you

have defined this automatically it will

take this particular signal and will

provide this kind of termination so let

us see how we can use the scale process

for our existing processes which we have

into our terminal and by using this

particular kill process will also ensure

that we have checked all the processes

and we have tracked something into the

process and killing the signals by using

- 15 - 9 as well