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sh script: problem with return value in function

This script is supposed to return the difference in time between two files,
simulator.o and discretizer.o. Instead, the it prints out a bunch of blank lines. It is as though the function I have defined is not properly returning a value. Any help is greatly appreciated! Thanks, Jameson

Code:

function get_time_diff() {

  disc_time=`stat --format=%Y $file2`

  sim_time=`stat --format=%Y $file1`

  raw_time=`expr $sim_time - $disc_time`



  # in case the files were specifed backwards, make sure time is positive.

  if [ `expr $raw_time` -lt 0 ]; then

    raw_time=`expr 0 - $raw_time`

  fi



  if [ $1="h" ]; then

    return `expr $raw_time / 3600`

  elif [ $1="m" ]; then

    return `expr $raw_time / 60`

  elif [ $1="s" ]; then

    return $raw_time

  else

    return `expr $raw_time / 60`

  fi

}



unit=$1

dir_list=`ls -ad */`



for directory in $dir_list ; do

  if [ -f $directory/simulator.o ]; then

    file1=$directory/simulator.o

    if [ -f $directory/decomposer.o -o -f $directory/discretizer.o ]; then

      if [ -f $directory/decomposer.o ]; then

        file2=$directory/decomposer.o

      elif [ -f $directory/discretizer.o ]; then

        file2=$directory/discretizer.o

      else

        echo "No decomposer.o or discretizer.o found in dir." >&2

      fi

      echo `get_time_diff $unit`

    fi

  else

    echo "No simulator.o found in this dir." >&2

  fi

done

The best way to "return" data from a shell script function is to have that function send the data to standard output, rather than using the bash return statement, because the return code which is sent back by the return statement is a relatively small integer which shows success or failure. Indeed, you show that you expect the result from your function to come via standard output when you say:

Code:

echo `get_time_diff $unit`

The problem is that your function doesn't send its output to standard output; it tries to return that value via the return statement. Instead of this:

Code:

return $raw_time

say

Code:

echo $raw_time

and instead of

Code:

return `expr $raw_time / 60`

say

Code:

expr $raw_time / 60

And so on.

Hope this helps.