Shell Programming and Scripting

HI,

I have a strange problem. A shell script that runs fine on solaris. when i ported to linux, it started hanging.

here is the core of the script

Code:

CFG_FILE=tab25.cfg
sort -t "!" -k 2 ${CFG_FILE} | egrep -v "^#|^$" |  while IFS="!" read  a b c
do
#echo "jobs output"
#jobs
#echo "jobs -p  "
#jobs -p
# echo "Before entering parallel process  $$ "
#                jobs  -l
#if [[ `jobs | wc -l` -ne 0 ]] ; then
#               jobs|wc -l
#                ps -ef|grep "`jobs -p`"
#fi
 
wait
done

my CFG_FILE is

Code:

this_is_a_test_ttt! lask;djfl;a ljkasfl; as l;jsladfjasldfj aslk;fjas flj;asf fABCDEFGHIJ KLMNOP ABCDELKJ :LKJSDFLKJSDFKLJDFKDJF  DFKSDHFIUI JSF SIDFJISDFISJDIF  ! lkjasdflkjasf

repeated for 32 times.


if i uncomment the body of while loop , here is the output (that shows what for "wait" is waiting)

Code:

[2] +  Running                 <command unknown>
[1] -  Running                 <command unknown>
jobs -p  
28418

Before entering parallel process 28416

Code:

[2] + 28418      Running                 <command unknown>
       1 
myid   28418 28416  0 14:26 pts/31   00:00:00 egrep -v ^#|^$
myid   28421 28416  0 14:26 pts/31   00:00:00 ps -ef
myid   28422 28416  0 14:26 pts/31   00:00:00 grep 28421?28418

what causes this script wait for a while/grep command in linux whereas in solaris it is fine.

To give further details, i suppose to call a (8) background process, for each of line read from the file. So i introduced a wait command and when all complete i read next line and so on.
Since wait was really waiting for grep and not for spawned child, my script broke.

Othercases when it can run fine in linux

1. fewer lines in config file
2. in one test, i shrink one of row length from 260 to 250, it worked.

i can't predict a consitance condition for this behaviour.

Any help is appreciated in fixing / explaining this behaviour.

thanks
AK

I regret that I can't decipher what you are actually trying to acheive, however my bet is that from earlier testing you may have a background task still hanging around and the wait command is watching for all background processes to finish (jobs 1 & 2 running unknown command). Try starting a new session to ensure that is not your problem.


I hope that this helps.

Robin
Blackburn/Liverpool
UK

What shells are you using on Gnu/Linux and on Solaris ?

my apologizes for not using tag . and thanks for tagging.

1.
in both machines, i use ksh my program starts #!/bin/ksh , so it should override any shell is being used.

2. to answer the scenario , Robin's guess is right.
here is what i am doing

Code:

 
 
while read table, server_list
do
 
for server in server_list
do
do_somthing with table and server & # in background
done
wait # wait for all my background jobs to finish. 
echo now i can go and read next line 
 
done

now in my cash, wait started waiting for a zombie (unknown command, evetually a grep , sort) and never come out to read next line.

when i was trying to simplify the problem, i removed inner for loop , so my question looks awkward(stupid?)
technically, when i have while loop and have a wait command it shouldn't wait. ofcourse linux does something in background for while loops

i even used a intermediate file for doing sort and grep output and pass it on to while loop, but wait continue to hang.


again, when i started my config file with few lines, it was working fine in linux too. when i started adding more and more lines, it gave error

at one point, when i reduced row length from 260 char to 250 char , it worked too. but script still can work with line length exceeding more than 250 char when fewer lines were there. so i can't say this is the only scenario problem is exhibited.


could somebody help me to understand this..

thanks
AK

What ksh implementation are you using on Gnu/Linux, the real one or pdksh ?

i don't know if i am using pdksh and realksh (i never heard pdksh earlier)
anyway, here is my output
/bin/ksh --version
version sh (AT&T Labs Research) 1993-12-28 n+

seems to be real?

thx

Yes, that's the real one. What version on the Solaris side ?