[TUHS] question about V7 ls(1) vs. sys/stat.h and ls.c

[TUHS] question about V7 ls(1) vs. sys/stat.h and ls.c

[Michael Sokolov]

Chris Palmer <chris at nodewarrior.org> wrote:

> What's with that "511" in there?

To divide by N rounding up you first add N-1, then divide by N.

MS

[TUHS] question about V7 ls(1) vs. sys/stat.h and ls.c

[Kirk McKusick]

The st_blocks field was first added to the stat structure in 4.2BSD
(4.1b really) as part of the overhaul to add the new filesystem. I
added it because the variable filesystem blocksize made it difficult
to compute the amount of storage dedicated to a file.

	Kirk McKusick

[TUHS] question about V7 ls(1) vs. sys/stat.h and ls.c

[Aharon Robbins]

Greetings all.

The V7 ls(1) man page says that the -s option, which prints total
blocks, includes any indirect blocks.

However, the V7 struct stat didn't have the st_blocks member in the
struct stat, and the code in ls.c uses

	long
	nblock(size)
	long size;
	{
		return((size+511)>>9);
	}

So, is this just a case of the man page being mistaken?

When did the struct stat acquire the st_blocks member?

While I'm at it, the V7 ls -a option only adds . and .. to the
list; apparently all other dot files were printed by default.
When did ls change such that -a applied to all dot files?

Thanks,

Arnold Robbins

[TUHS] question about V7 ls(1) vs. sys/stat.h and ls.c

[Chris Palmer]

Aharon Robbins writes:

> 	long
> 	nblock(size)
> 	long size;
> 	{
> 		return((size+511)>>9);
> 	}

Unfortunately I can't answer any of your questions; I can only ask a new
one: What's with that "511" in there?

[TUHS] question about V7 ls(1) vs. sys/stat.h and ls.c

[M. Warner Losh]

In message: <20030523033209.GE29449 at nodewarrior.org>
            Chris Palmer <chris at nodewarrior.org> writes:
: Aharon Robbins writes:
: 
: > 	long
: > 	nblock(size)
: > 	long size;
: > 	{
: > 		return((size+511)>>9);
: > 	}
: 
: Unfortunately I can't answer any of your questions; I can only ask a new
: one: What's with that "511" in there?

It rounds size up to the next larger block, and >> 9 divides by 512.
So if you size was 512 it would return '1' but if it was 513 it would
return '2'.

Warner

[TUHS] question about V7 ls(1) vs. sys/stat.h and ls.c

[Greg 'groggy' Lehey]

On Thursday, 22 May 2003 at 20:32:09 -0700, Chris Palmer wrote:
> Aharon Robbins writes:
>
>> 	long
>> 	nblock(size)
>> 	long size;
>> 	{
>> 		return((size+511)>>9);
>> 	}
>
> Unfortunately I can't answer any of your questions; I can only ask a new
> one: What's with that "511" in there?

Sector size - 1, just like the 9 is log(2) (511).  It converts bytes
to sectors.

Greg
--
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