#!/bin/bash
#
# script to combine separate data files to produce something gnuplot's 
# histogram feature can use.
#
# filenames hardcoded for the example of interest, but this could be
# revised to be more general.
#
# (yes, writing the script was a lot more work than just combining and
# editing the files with paste and vim, but it was more fun?)
#
infiles="c-library.dat java-library.dat lcg.dat"
outfile=combined.dat

tmp=tmp-$$
tmptmp=tmp-tmp-$$

# extract first column from data, checking that it matches in all files
for f in $infiles
do
    awk '{ print $1 }' < $f > $tmptmp
    if [ -e $tmp ]
    then
        cmp $tmp $tmptmp 1>/dev/null 2>/dev/null
        if [ $? -ne 0 ]
        then
            echo "first columns do not match"
            exit 1
        fi
    else
        mv $tmptmp $tmp
    fi
done

# extract second column from each file and combine with previous result
for f in $infiles
do
    awk '{ print $2 }' < $f | paste $tmp - > $tmptmp
    mv $tmptmp $tmp
done
( 
    echo -n "#" 
    for f in $infiles; do echo -n " $f"; done
    echo ""
    cat $tmp
) > $outfile

rm $tmp