internal working of echo command
 

can i know how does an echo command works internally. offcourse it is generally used to print a msg. how does it calls the msg

1/ Why would you need to know this?
2/ I'm sure you can dive into the sources - typically by getting a copy of the "developer" release of the package that contains your "echo".
3/ Which Linux distribution are you running?

reason for knowing the internal working of echo command
 

sir actually i am under going a training on linux. In which we were asigned tasks. the question which i asked is one of my task and can't find a proper answer for this question on net. I would be thank full if u can help me with this task.

These Forums are not the right place to assist with homework or similar tasks.
Pay attention to the course and you will find the answer...

When you write "how does it calls the msg" do you mean "where does it get the message from" or "where does it output the message to"?

Issue the following command on a terminal:

U will see a list of system calls that get invoked in a sequential order on executing echo command. See if that helps you !

Out of curiosity I did so. It ran the external command "echo" rather than the shell built-in (of course). Fascinating output clearly showing . . . how much I don't know about system calls :confused: I guess *n*x has moved on since Richard Stevens wrote the wonderfully lucid "Advanced Programming in the UNIX Environment"

It might seem a dumb question, but still I want to know that how did u find out that it was an external command instead of the shell built-in ?

I happen to know that echo is a built-in but could have found out using this at a ommand promptThe strace output included this line showing it was running the external command /usr/bin/echo

Thanks for the reply!

I didn't pay attention to the line pointed out by u due to my absent-mindedness :D

for both

What was this statement ?

mean "where does it get the message from" or "where does it output the message to"?

It gets the message from the command line and sends it to stdout. Here's from echo's man page

As catkin said, echo doesn't call the message, it receives the message an input from the user. Its default job is to send the received message to the standard output, but you can redirect its output to some file of your choice !

e.g:
Here the input string i.e. mohit_parihar will be appended at the end of the file temp.c located on your desktop folder!