LDP/LDP/guide/docbook/abs-guide/col-totaler2.sh

#!/bin/bash

#  Another version of the "column totaler" script
#+ that adds up a specified column (of numbers) in the target file.
#  This one uses indirect references.

ARGS=2
E_WRONGARGS=85

if [ $# -ne "$ARGS" ] # Check for proper number of command-line args.
then
   echo "Usage: `basename $0` filename column-number"
   exit $E_WRONGARGS
fi

filename=$1         # Name of file to operate on.
column_number=$2    # Which column to total up.

#===== Same as original script, up to this point =====#


# A multi-line awk script is invoked by
#   awk "
#   ...
#   ...
#   ...
#   "


# Begin awk script.
# -------------------------------------------------
awk "

{ total += \$${column_number} # Indirect reference
}
END {
     print total
     }

     " "$filename"
# Note that awk doesn't need an eval preceding \$$.
# -------------------------------------------------
# End awk script.

#  Indirect variable reference avoids the hassles
#+ of referencing a shell variable within the embedded awk script.
#  Thanks, Stephane Chazelas.


exit $?