[SOLVED] Partial string search between two files using AWK

Issue

I have been trying to re-write an egrep command using awk to improve performance but haven't been successful. The egrep command performs a simple case insensitive search of the records in file1 against (partial matches in) file2. Below is the command and sample output.

file1 contains:

Abc
xyz
123
blah
hh
a,b

file2 contains:

abc de
xyz
123
456
blah
test1
abdc
abc,def,123
kite
a,b,c

Original command : egrep -i -f file1 file2

Original (egrep) command output :

$ egrep -i -f file1 file2
abc de
xyz
123
blah
abc,def,123
a,b,c

I would like to use AWK to rewrite the command to do the same operation. I have tried the below but it is performing a full record match and not partial like grep does.

Modified command in awk : awk 'NR==FNR{a[tolower($0)];next} tolower($0) in a' file1 file2

Modified command (awk) output:

$ awk 'NR==FNR{a[tolower($0)];next} tolower($0) in a' file1 file2
xyz
123
blah

This excludes the records which had partial matches for the string "abc". Any help to fix the awk command please? Thanks in advance.

Solution

Use index like this for a partial literal match:

awk '
NR == FNR {
  needles[tolower($0)]
  next
}
{
  haystack = tolower($0)
  for (needle in needles) {
    if (index(haystack, needle)) {
      print
      break
    }
  }
}' file1 file2

Answered By - oguz ismail

Answer Checked By - Marilyn (WPSolving Volunteer)