File status indicator for EOF?

steven.c.banks · 12-26-2007, 10:48 AM

I have the following script:

while read cos;
do
/root/robert/compare_one_cos_lab_mc1_mc2.sh $cos;
done < /tmp/coa2.txt

/tmp/coa2.txt has numberous lines in it, but the loop executes only once. I suspect that after the first call to the subscript, this script thinks it is at end of file, because the subscript reads other files in /tmp, so I need to save the file status before calling the subscript, and restore the file status on return so it will read the next record in /tmp/coa2.txt.

What is the file status flag for EOF, and how do I save it and restore it?

Thanks...

jschiwal · 12-26-2007, 11:54 AM

I don't think that is the problem.

Code:

cat test
line1
line2
line3

Code:

 while read line; do
> echo $line
> while read entry; do
> echo $entry
> done <test
> done <test
line1
line1
line2
line3
line2
line1
line2
line3
line3
line1
line2
line3

One problem with what you have posted is that if a line contains whitespace, the shell will break up $cos.

It also seems strange that you have a subdirectory in /root/. In linux /root is the home directory of the root user and you shouldn't be running normally as root. Did you mean to type "/home/" instead?

It also looks like some of the programs like diff and cmp from coreutils may be able to do what you want. I'm just guessing from the title of your script.

steven.c.banks · 12-26-2007, 12:20 PM

Thanks for your reply. The records in the file do not have any whitespace; just one field. Running scripts as root and using /root/robert was the practice before I was hired here, and not really relevant to this issue. The subscript has several diffs in it.

Is there an alternative way to read a file line by line?

steven.c.banks · 12-26-2007, 01:21 PM

I did some tracing within /root/robert/compare_one_cos_lab_mc1_mc2.sh by putting an exit after each statement to find out where the bogus end of file condition is coming from, and I found that after the following statement, when I return to the calling script, it thinks it is at end of file in /tmp/coa2.txt.

plink -ssh -pw xxxxxxxx root@y.y.y.y "/root/robert/get_cos_listing.sh $servicecat" > /tmp/mc1$servicecat

How do I prevent the above statement from setting the bogus end of file condition? plink is a PuTTY utility we use instead of rsh.

jschiwal · 12-26-2007, 05:33 PM

I don't believe that the line you posted effects the EOF of coa2.txt. If you had a line the redirected output to cao2.txt, then it would. Check if the plink command returns. It might operate like "exec" causing the current shell to be replaced.

steven.c.banks · 12-27-2007, 06:55 AM

A friend suggested I use this alternate method of reading the file line by line. I don't know why, but this fixed the problem.

exec 3< /tmp/coa2.txt
until [ $done ]
do
read <&3 cos
if [ $? != 0 ]; then
done=1
continue
fi
/root/robert/compare_one_cos_lab_mc1_mc2.sh $cos;
done