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Top Forums Shell Programming and Scripting Performance issue in UNIX while generating .dat file from large text file Post 302308916 by cfajohnson on Monday 20th of April 2009 03:21:38 PM
Originally Posted by KRAMA
We are facing some performance issue in UNIX. If someone had faced such kind of issue in past please provide your suggestions on this .

Problem Definition:
/Few of load processes of our Finance Application are facing issue in UNIX when they uses a shell script having below portion of code. The below portion of codes reads an input file and writes them into an .dat file. The performance issue arises when there is huge volume of data in the input file.
For example: For data volume having 200,000 records is taking 38 mins to get append/write into the .dat file which increases the complete load process timings. We need to increase the performance of this proces by reducing the time its taking to append/write the records.

With a file that size, you should really be using awk.

Portion of Code from Shell Script:

Please put code inside [code] tags.
cat ${m_recv_dir}/${m_glb_d92_nm}${m_glb_file_seq} |while read d92_line

That cat is an unnecessary external command, but since it is only run once, eliminating it wll make very little difference.

Part of the slowness is due to calling multiple external commands (many of which are unnecessary: there's no need for expr as the shell can do its own arithmetic) for every line.
m_brch_cd=`echo "${d92_line}" |cut -c166-168`

What shell are you using? If it's bash or ksh93, you can replace the call to cut:


for m_file_name in `echo ${m_a_d92_files[*]}`

An unnecessary subshell (here and later) can add a significant amount of time. Use:

for m_file_name in "${m_a_d92_files[@]"

if [[ `grep "*/" ${m_file_name} | wc -l` = 0 ]]

You don't need wc as well as grep:

if grep "*/" ${m_file_name} > /dev/null

echo "*/" >> ${m_file_name}
for m_file_name in `echo ${m_a_d92_list[*]}`
rm -f $m_file_name

Please provide your valuable suggestions. Also is there any way by using SED command for appending the output in fast way?
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