Shell Programming and Scripting

how to grep a file based on another input file

File1

ashu 1 ninetwo hari
qwer 6 givefour jan
fghj 8 noeight mar
vbmi 7 noput feb
--
---

File2

noput
noeight
---
--


Taking the input of grep as File2, a search need to be made in File1 giving File3 as output:

File3

vbmi 7 noput feb
fghj 8 noeight mar


i.e. only the lines from File1 with the matching string in File2 were printed into File3.

Please let me know how can this be accomplished through shell.

Thanks in anticipation

Code:

touch file3
cat file2 | while read a
      grep $a file1 >> file3
done

Code:

#!/usr/bin/ksh
for line in file2
do
   grep $line file1 >> file3
done

use this:-

Code:

nawk 'NR==FNR{a[$3]=$0 ; next} $1 in a{print a[$1]}' File1 File2 > File3

fgrep -f File2 File1 >File3

I sometime don't understand why people recommend awk and sed when it can be done with simple commands.Code needs to clean and understandable to the person writing it.

Code:

touch file3
cat file2 | while read a
      grep $a file1 >> file3
done

Your code is clean but you're using some redundant commands (cat, touch, read), this is sufficient:

Code:

grep -f file2 file1 > file3

Don't try to win the Useless Use of Cat Award.