Iterative Bash Script Bug - linux

Question

Using a bash script, I'm trying to iterate through a text file that only has around 700 words, line-by-line, and run a case-insensitive grep search in the current directory using that word on particular files. To break it down, I'm trying to output the following to a file:
Append a newline to a file, then the searched word, then another newline
Append the results of the grep command using that search
Repeat steps 1 and 2 until all words in the list are exhausted
So for example, if I had this list.txt:
search1
search2
I'd want the results.txt to be:
search1:
grep result here
search2:
grep result here
I've found some answers throughout the stack exchanges on how to do this and have come up with the following implementation:
#!/usr/bin/bash
while IFS = read -r line;
do
"\n$line:\n" >> "results.txt";
grep -i "$line" *.in >> "results.txt";
done < "list.txt"
For some reason, however, this (and the numerous variants I've tried) isn't working. Seems trivial, but I'd it's been frustrating me beyond belief. Any help is appreciated.

Answer 1

Your script would work if you changed it to:
while IFS= read -r line; do
printf '\n%s:\n' "$line"
grep -i "$line" *.in
done < list.txt > results.txt
but it'd be extremely slow. See https://unix.stackexchange.com/questions/169716/why-is-using-a-shell-loop-to-process-text-considered-bad-practice for why you should think long and hard before writing a shell loop just to manipulate text. The standard UNIX tool for manipulating text is awk:
awk '
NR==FNR { words2matches[$0]; next }
{
for (word in words2matches) {
if ( index(tolower($0),tolower(word)) ) {
words2matches[word] = words2matches[word] $0 ORS
}
}
}
END {
for (word in words2matches) {
print word ":" ORS words2matches[word]
}
}
' list.txt *.in > results.txt
The above is untested of course since you didn't provide sample input/output we could test against.

Answer 2

Possible problems:
bash path - use /bin/bash path instead of /usr/bin/bash
blank spaces - remove ' ' after IFS
echo - use -e option for handling escape characters (here: '\n')
semicolons - not required at end of line
Try following script:
#!/bin/bash
while IFS= read -r line; do
echo -e "$line:\n" >> "results.txt"
grep -i "$line" *.in >> "results.txt"
done < "list.txt"

Answer 3

You do not even need to write a bash script for this purpose:
INPUT FILES:
$ more file?.in
::::::::::::::
file1.in
::::::::::::::
abc
search1
def
search3
::::::::::::::
file2.in
::::::::::::::
search2
search1
abc
def
::::::::::::::
file3.in
::::::::::::::
abc
search1
search2
def
search3
PATTERN FILE:
$ more patterns
search1
search2
search3
CMD:
$ grep -inf patterns file*.in | sort -t':' -k3 | awk -F':' 'BEGIN{OFS=FS}{if($3==buffer){print $1,$2}else{print $3; print $1,$2}buffer=$3}'
OUTPUT:
search1
file1.in:2
file2.in:2
file3.in:2
search2
file2.in:1
file3.in:3
search3
file1.in:4
file3.in:5
EXPLANATIONS:
grep -inf patterns file*.in will grep all the file*.in with all the patterns located in patterns file thanks to -f option, using -i forces insensitive case, -n will add the line numbers
sort -t':' -k3 you sort the output with the 3rd column to regroup patterns together
awk -F':' 'BEGIN{OFS=FS}{if($3==buffer){print $1,$2}else{print $3; print $1,$2}buffer=$3}' then awk will print the display that you want by using : as Field Separator and Output Field Separator, you use a buffer variable to save the pattern (3rd field) and you print the pattern whenever it changes ($3!=buffer)