grep command in bash shell loop [duplicate]

Question

I have a log file, name out.log. I need to search a list of string (filelist.txt) from this log file.

I need each matching line from "out.log" for every file in filelist.txt. it can appear multiple times.

cat out.log | grep -i I466030.CXR910E >> search_result.txt

this works, it will search for I466030.CXR910E and output to search_result.txt

for i in `cat filelist.txt`; do  grep -i "$i" out.log >> result.txt; done


 for i in `cat filelist.txt`; 
   do  
     echo $i
     cat out.log | grep -i $i >> result2.txt
     grep $i out.log >> result3.txt 
  done 

Above code the echo will output the search string but none of the grep not writing output to any result*.txt

What am I missing here ? Thanks for your advice.

---

In response to comments:

xxxxxm@cxxxrtrls01[DEV][rerun] $ grep -i -f filelist.txt out.log > result.txt
xxxxxm@cxxxrtrls01[DEV][rerun] $ ll
total 564
-rw-r----- 1 cnrlsadm cnrlsadm   4600 Aug 19 09:36 filelist.txt
-rw-r----- 1 cnrlsadm cnrlsadm    216 Aug 19 10:14 file.sh
-rw-r--r-- 1 cnrlsadm cnrlsadm 557403 Aug 19 10:10 out.log
-rw-r--r-- 1 cnrlsadm cnrlsadm      0 Aug 19 12:14 result.txt
-rw-r----- 1 cnrlsadm cnrlsadm    213 Aug 19 12:10 srch.sh
xxxxxm@cxxxrtrls01[DEV][rerun] $

size of result.txt is zero , it doesnt have anything.

Answer 1

1. Don't read the lines of a file with for

2. use grep's -f option to supply a file containing patterns so you don't need to loop at all:

   grep -i -f filelist.txt out.log > result.txt
   

   You now have a single invocation of grep, instead of one per line. If out.log is large, your CPU will thank you.

Answer 2

Well.. most of the reply here are correct, its my bad the "filelist.txt" was generated from excel and in windows. Once I convert the file into unix format. everything worked.

I learned a very time-consuming lesson. Thanks a million to every one answered the question :)

Have a great day ahead !

Answer 3

Tried with below script and it worked fine

for i in `cat filelist.txt`
do
for j in `cat out.log`
do
grep -i "$j" $i
done
done

filelist.txt.====> Consists of filenames