command execution - Linux Forums

05-26-2009	#1 (permalink)
happy-linux Just Joined! Join Date: Apr 2009 Posts: 18	command execution when a command is enterted how does it display the output on screen..... what is the internal working???

05-26-2009

#2 (permalink)

Lakshmipathi

Linux Engineer

Join Date: Sep 2006

Location: 3rd rock from sun

Posts: 1,093

Quote:

when a command is enterted how does it display the output on screen..... what is the internal working???

I assume commands are nothing but C program, These executable are place under specific path.
Example : main,c

Quote:

int main(){
printf("\n Linux Programmers Paradise\n");
return 1;
}

Compile it

Quote:

gcc -o main main.c

move to pre-defined path

Quote:

mv main /usr/bin

Now open any terminal and run the "command" called main.If You upload this "main" command to sites like sourceforge.net.If people find the software useful ,they will download your program and use it.

That's how open source works

__________________
- Lakshmipathi.G
-------------------
FOSS India Award winning ext3fs Undelete tool and tutorials www.giis.co.in
First they criticize you,Then they laugh at you,Then they fight with you,Then you win. - M.K.Gandhi
-------------------

05-27-2009

#3 (permalink)

happy-linux

Just Joined!

Join Date: Apr 2009

Posts: 18

Quote:

Originally Posted by Lakshmipathi

I assume commands are nothing but C program, These executable are place under specific path.
Example : main,c

Now open any terminal and run the "command" called main.If You upload this "main" command to sites like sourceforge.net.If people find the software useful ,they will download your program and use it.

That's how open source works

thanx, but my question is different, i wanna know how does a OUTPUT display on SCREEN

e.g. if i typed
$ echo hello
hello will be displayed, how this happens........

05-27-2009

#4 (permalink)

Lakshmipathi

Linux Engineer

Join Date: Sep 2006

Location: 3rd rock from sun

Posts: 1,093

Quote:

e.g. if i typed
$ echo hello
hello will be displayed,

Quote:

int main(int argc,char * argv[]){
printf("%s",argv[1]);
return 1;
}

compile it as

Quote:

gcc - echo2 main.c

Run it as

Quote:

./echo2 hello

05-27-2009	#5 (permalink)
Lakshmipathi Linux Engineer Join Date: Sep 2006 Location: 3rd rock from sun Posts: 1,093	By fault screen is your output device - Keyboard is your input device if you want know about how printf() works then i would suggest to check with some system programming books like rebecca thomas Unix Programmer Guide __________________ - Lakshmipathi.G ------------------- FOSS India Award winning ext3fs Undelete tool and tutorials www.giis.co.in First they criticize you,Then they laugh at you,Then they fight with you,Then you win. - M.K.Gandhi -------------------

05-28-2009

#6 (permalink)

happy-linux

Just Joined!

Join Date: Apr 2009

Posts: 18

Quote:

Originally Posted by Lakshmipathi

By fault screen is your output device - Keyboard is your input device

if you want know about how printf() works then i would suggest to check with some system programming books like rebecca thomas Unix Programmer Guide

can u plz suggest me some links on internet........... i wanna know abt the internal working of eho command of linux.

05-28-2009	#7 (permalink)
Lakshmipathi Linux Engineer Join Date: Sep 2006 Location: 3rd rock from sun Posts: 1,093	If you want to know about working for echo ,then better check its source code with coreutils. echo source code : http://www.google.com/codesearch/p?h...utils%20lang:c coreutils download page Coreutils - GNU core utilities All the best __________________ - Lakshmipathi.G ------------------- FOSS India Award winning ext3fs Undelete tool and tutorials www.giis.co.in First they criticize you,Then they laugh at you,Then they fight with you,Then you win. - M.K.Gandhi -------------------

05-28-2009

#8 (permalink)

happy-linux

Just Joined!

Join Date: Apr 2009

Posts: 18

Quote:

Originally Posted by Lakshmipathi

If you want to know about working for echo ,then better check its source code with coreutils.

echo source code :

coreutils
All the best

thankyou very very much for the links........ if u know more abt echo then send me the updates.

thanx again.

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