Using case instead of grep

Shell Programming and Scripting
1

im using a case statement to search for a pattern in a variable, like this:

case "${VARIABLE}" in
* unix is great *)
    echo Found it!
;;
esac

However, what happens if I want to make sure some other string DOES NOT exist on the same line that "unix is great" is on??

with egrep, i can solve it with something like:

echo "${VARIABLE}" | egrep -v "bad lines i dont want" | egrep "unix is great"

I'm hoping there's a way to do this in case, without having to use any external tools.

2

Try:

case $VARIABLE in 
  *"bad lines i dont want"*)
    :                            
  ;;
  *"unix is great"*)
    echo "Found: $VARIABLE"
  ;;
esac
1 Like
3

I tried this but it didn't seem to work. when i run it, i get nothing back. just the prompt.

#!/bin/sh

VARIABLE='bad lines i dont want
unix is great'
case ${VARIABLE} in 
  *"bad lines i dont want"*)
    :                            
  ;;
  *"unix is great"*)
    echo "Found: $VARIABLE"
  ;;
esac

And I tried putting the variable in quotes:

#!/bin/sh

VARIABLE='bad lines i dont want
unix is great'
case "${VARIABLE}" in 
  *"bad lines i dont want"*)
    :                            
  ;;
  *"unix is great"*)
    echo "Found: $VARIABLE"
  ;;
esac

neither worked

4

Of course not. There is only one variable and the expansion of that variable contains the string bad lines i don't want which is matched by the 1st pattern in your case statement (which produces no output).

If you're dealing with a variable containing multiple lines and you want to process each line separately, you need something more like:

#!/bin/sh
VARIABLE='this line should not print -- bad lines i dont want
this line should print -- unix is great
neither of the above'

printf "%s\n" "$VARIABLE" | while IFS= read -r line
do	case "$line" in
	*"bad lines i dont want"*)	echo "1st case: $line";;
	*"unix is great"*)		echo "2nd case: Found: $line";;
	*)				echo "default case: No match: $line";;
	esac
done

which produces the output:

1st case: this line should not print -- bad lines i dont want
2nd case: Found: this line should print -- unix is great
default case: No match: neither of the above
2 Likes
5

The behaviour of the case statement matches what your need actually.
see:

$ cat case.sh
for VARIABLE in 'bad lines i dont want unix is great' 'bad line ... unix is great'
do
((LOOP+=1))
case ${VARIABLE} in
  *"bad lines i dont want"*)
    echo "Loop : $LOOP :CASE 1: $VARIABLE"
  ;;
  *"unix is great"*)
    echo "Loop : $LOOP :CASE 2: $VARIABLE"
  ;;
esac
done

$ ./case.sh
Loop : 1 :CASE 1: bad lines i dont want unix is great
Loop : 2 :CASE 2: bad line ... unix is great