Bash script hangs

Question

I have the code below. Basically this code will ls -tr $FROM_DIRECTORY then redirect the output to /tmp/msc.load.tmp. After this a for loop will execute and move the first 3000 files to another directory. The code is working fine but sometimes it will hang. I have no idea why it hangs. Anyone know what is the problem of the script?

ls -tr $FROM_DIRECTORY > /tmp/msc.load.tmp
echo "$sysdate -- Listing Diretory " >>$LOGFILE
# From the file list, get the 3000 from the top to move. Skip the remaining files in the list 
# in this iteration. 
# Version 1.1 - List the files from the temporary file.  
for file in $(cat /tmp/msc.load.tmp | grep 'MSCERC.*' | head -3000 )
do 
   mv $FROM_DIRECTORY/$file $DESTINATION_DIRECTORY
done
echo "$sysdate -- End of Script " >>$LOGFILE
exit 0
# End of script.

It would be better to just use the find command and dispense with the intermediate file. — Keith
– Keith, Commented Aug 7, 2011 at 7:12
run it with "bash -x" so you'll be able to see where and probably why did it hang — hmontoliu
– hmontoliu, Commented Aug 7, 2011 at 7:23
I new to unix..May i know how to add -x in the script ? Can gv some example ? — user871695
– user871695, Commented Aug 7, 2011 at 7:58
The cat, the head, and the regex wildcard are all unnecessary. Also, don't read lines with for. grep -m 3000 MSCERC /tmp/msc.load.tmp | while read -r file; do ... Finally, quote your variables. — tripleee
– tripleee, Commented Feb 28, 2019 at 13:24

Yuri · Accepted Answer · 2022-05-18 07:24:38Z

4

Yeap, try a find.

Also if you're not aware of it, the set -x command is valuable in situations like this. My approach is to add set -x to the top of the script and then run it with output redirected to a file. capturing both standard out and standard error

./script.sh > output.txt 2>&1

If you want you can tail -f output.txt in another window to monitor progress.

set -x echos the commands run and the redirection puts the command and output into chronological order.

edited May 18, 2022 at 7:24

Yuri

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answered Aug 7, 2011 at 7:17

Karl

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5 Comments

Ignacio Vazquez-Abrams Over a year ago

Which part guarantees that stdout and stderr will be in chronological order?

Karl Over a year ago

The writing of lines cronologically. As opposed to trying to relate the stderr from the console and stdout from a redirect without the stderr part.

Ignacio Vazquez-Abrams Over a year ago

But there are still no guarantees that they will be written out in sync. I mean, yes, it's better than having them go to two separate destinations, but if the streams are flooded then they will not necessarily be output in order. But I guess the asker will have to take their chances.

user871695 Over a year ago

I new to unix..May i know how to set -x in the top of the script ? Can gv some example ?

Karl Over a year ago

Either call the script with the -x parameter as hmontoliu says above or edit your script and above the line ls -tr $FROM_DIRECTORY > /tmp/msc.load.tmp enter set -x

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