Compare output of program to correct program using bash script, without using text files

I've been t开发者_开发技巧rying to compare the output of a program to known correct output by using a bash script without piping the output of the program to a file and then using diff on the output file and a correct output file.

I've tried setting the variables to the output and correct output and I believe it's been successful but I can't get the string comparison to work correctly. I may be wrong about the variable setting so it could be that.

What I've been writing:

TEST=`./convert testdata.txt < somesampledata.txt`
CORRECT="some correct output"
if [ "$TEST"!="$CORRECT" ];
then
  echo "failed"
fi

if [ "$TEST!"!="$CORRECT" ];

Looks like you have an extra ! in $TEST!.

This works for me...

$ echo "foobar" > /tmp/test; TEST=`tail -n1 < /tmp/test`; CORRECT="foobar"; if [ "$TEST" != "$CORRECT" ]; then echo "failed"; fi
$

This fails for me...

$ echo "barfoo" > /tmp/test; TEST=`tail -n1 < /tmp/test`; CORRECT="foobar"; if [ "$TEST" != "$CORRECT" ]; then echo "failed"; fi
failed

Problem was that I was using an incorrect string for my correct output, so it always failed.

correction:

TEST=`./convert testdata.txt < BothKnownZero.txt`
CORRECT=$'Enter original quantity, original units, new units\n0.0000 miles equals 0.0000 feet'
echo $TEST
echo $CORRECT
if [ "$TEST" != "$CORRECT" ]
then
    echo "failed "
fi

If you have zsh available you can use the =(cmd) construct, it saves the output of cmd to a temporary file which is deleted when the command returns:

if ! diff -q known_good =(cmd); then
  # do something if they differ
fi