bash search for string in each line of file

Question

I'm trying what seems like a very simple task: use bash to search a file for strings, and if they exist, output those to another file. It could be jetlag, but this should work:

#!/bin/bash

cnty=CNTRY

for line in $(cat wheatvrice.csv); do
    if [[ $line = *$cnty* ]]
    then
        echo $line >> wr_imp.csv
    fi
done

I also tried this for completeness:

#!/bin/bash

cnty=CNTRY

for line in $(cat wheatvrice.csv); do
    case $line in 
    *"$cnty"*) echo $line >> wr_imp.csv;;
    *) echo "no";;
    esac
done

both output everything, regardless of whether the line contains CNTRY or not, and I'm copy/pasting from seemingly reliable sources, so apparently there's something simple about bash-ness that I'm missing?

Answer 1

Don't use bash, use grep.

grep -F "$cnty" wheatvrice.csv >> wr_imp.csv

Answer 2

While I would suggest to simply use grep too, the question is open, why you approach didn't work. Here a self referential modification of your second approach - with keyword 'bash' to match itself:

#!/bin/bash

cnty=bash    
while read -r line
do
    case $line in 
        *${cnty}*) 
            echo $line " yes" >> bashgrep.log
            ;;
        *)
                echo "no"
                ;;
    esac
done < bashgrep.sh

The keypoint is while read -r line ... < FILE. Your command with cat involves String splitting, so every single word is processed in the loop, not every line.

The same problem in example 1.