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From: paradis@encore.UUCP (Jim Paradis)
Newsgroups: comp.os.minix
Subject: More on sh/shar
Message-ID: <1643@encore.UUCP>
Date: Thu, 28-May-87 10:42:46 EDT
Article-I.D.: encore.1643
Posted: Thu May 28 10:42:46 1987
Date-Received: Sat, 30-May-87 07:41:58 EDT
Organization: Encore Computer Corp., Marlboro, MA
Lines: 39

Remember my last message complaining about /bin/sh being unable to
unpack "real" shell archives?  Well, last night I got SO sick&tired
of the situation that I took a deep breath and dove head-first into
the code for /bin/sh.  Getting it to compile was a feat unto itself...
(seems the MINIX compiler handles globals and externs differently
from the PC/IX compiler...). 

Side note:  Why is it that command interpreter code is almost ALWAYS
devoid of useful comments?  I've had to swim around in System V sh,
BSD4.2 csh and MINIX sh, and in all three cases the only useful
comments in the code were those added after the fact by the local
developers...

Anyway, after dredging through the code, I found that my worst fears
were indeed true:  on "<<" input redirections, sh does indeed try to
read the ENTIRE redirected input into memory.  What's REALLY stupid
is that when it actually goes to feed the redirected input into a
command, it creates a temporary file and writes the data out to the
file.  Why not just dump the data into the temporary file in the
first place and skip the memory-hogging?  What's REALLY REALLY stupid
is that after it creates the temp file, it doesn't bother to release
the memory that was used to store the data!!

Anyhow, I modified the shell so as to read the data in and dump
it directly into a temporary file -- the only in-memory buffering
is that of the line currently being read (limit of 512 chars).
The damn thing actually worked the first time, too!  Anyway, as soon
as I'm done cleaning up the code a bit (making sure it releases all 
the memory it allocates, making sure it properly deletes the temporary
file, etc). I'll post the changes for all to share.  I'll also post
the changes that were required for me to recompile the thing under
MINIX...

   +----------------+  Jim Paradis                  linus--+
+--+-------------+  |  Encore Computer Corp.       necntc--|
|  | E N C O R E |  |  257 Cedar Hill St.           ihnp4--+-encore!paradis
|  +-------------+--+  Marlboro MA 01752           decvax--|
+----------------+     (617) 460-0500             talcott--+
You don't honestly think ENCORE is responsible for this??!!