bash sucks lots of RAM doing read & echo in loop

[wojtek]

Configuration Information [Automatically generated, do not change]:
Machine: i386
OS: freebsd6.2
Compiler: cc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='i386' 
-DCONF_OSTYPE='freebsd6.2' -DCONF_MACHTYPE='i386-portbld-freebsd6.2' 
-DCONF_VENDOR='portbld' -DLOCALEDIR='/usr/local/share/locale' -DPACKAGE='bash' 
-DSHELL  -DHAVE_CONFIG_H   -I.  -I. -I./include -I./lib  -I/usr/local/include 
-O2 -fno-strict-aliasing -pipe -march=pentium3
uname output: FreeBSD wojtek.tensor.gdynia.pl 6.2-RELEASE-p10 FreeBSD 
6.2-RELEASE-p10 #0: Tue Jan 15 16:35:37 CET 2008     
root@FreeSBIE.LiveCD:/usr/src/sys/i386/compile/p234  i386
Machine Type: i386-portbld-freebsd6.2

Bash Version: 3.2
Patch Level: 17
Release Status: release

Description:
        bash keeps all output it echoed in memory.
        in my case it sucked over 3GB VM processing 2.5GB file.
        details in "Repeat-By:"

Repeat-By:
        such fragment of my script is executed

        while read ll;do  echo $RANDOM $RANDOM $ll; done <$tmp2 | $SORT | cut 
-f 3- -d " " >$tmp3

        where $tmp2 is 2.5GB input file, $tmp3 is output file and $SORT is 
"sort -S 512m"

        this routine has to randomize lines of input file $tmp2.

        and it works fine, but WHY bash gets over 3GB size, which grows as it 
processes $tmp2
        input?
        
        it should not keep anything in memory but pipe to sort program (which 
takes 512MB as
        i wanted it+tempfiles). but it does both.

Fix: