A question on cat.asm from asmutils-0.17

A question on cat.asm from asmutils-0.17

[Lawrence]

Hi All,

I'm trying to get acquintant with Linux assembly language by studying
the asm code found in asmutils.

While studying cat.asm, I discover that every time a file is opened
using sys_open, there is no correspondent sys_close to it. (The codes
were marked).

I would like to ask if this is an legitimate way to open a file without
closing it under Linux, or just a convenient way to let the
shell/kernel(I'm not sure...) to close the file for us when cat is
finished.  For my experience on MS-DOS assembly, I must close an
opened-file, or otherwise I'll encounter an out of file handle error.

Thanks and Regards,
Lawrence

Re: A question on cat.asm from asmutils-0.17

[Frederic Marmond]

Hi,
One of the goal of asmutils is to be as small as possible.
So, any 'non-very-necessary' things are commented out to save place.

In Linux, when you open  file, a file descriptor is stored in the 
process memory.
When you release the process, the system close all its opened files.
So, what is done in cat.asm is *not* a nice thing (every thing that is 
opened must in theory be closed) but it is a good way to reduce code 
size (from few bytes, but it is the power of assembly) without breaking 
anything.

hope it helps
Fred

Lawrence wrote:

>Hi All,
>
>I'm trying to get acquintant with Linux assembly language by studying
>the asm code found in asmutils.
>
>While studying cat.asm, I discover that every time a file is opened
>using sys_open, there is no correspondent sys_close to it. (The codes
>were marked).
>
>I would like to ask if this is an legitimate way to open a file without
>closing it under Linux, or just a convenient way to let the
>shell/kernel(I'm not sure...) to close the file for us when cat is
>finished.  For my experience on MS-DOS assembly, I must close an
>opened-file, or otherwise I'll encounter an out of file handle error.
>
>Thanks and Regards,
>Lawrence
>
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