#!/bin/sh 
# do_h2o2: find day containing most measurements for H2O2
# usage: do_h2o2 file
# output: Year H2O2 ppbv
#         178.010417 0.17
#         178.024306 0.18


# first do some command-line checking
if [ $# -ne 1 ]; then printf "usage: do_h2o2 file\n"; exit; fi
if [ ! -f "$1" ]; then printf "file: $1 does not exist\n"; exit; fi

# prompt for output filename
printf "\nPlease enter output filename:\n"
read outname


# find day with most measurements
# save to variable: frequent
frequent=`
cat $* |
cut -c1-3 |
sort |
uniq -c |
sort +0rn |
head -1 |
field -2`

printf "\nprocessing file: $1, day number: $frequent\n"

printf "Year H2O2 ppbv\n" > $outname

# get most-frequently occurring day from input file
grep "^$frequent" "$1" |
tr '	' ' ' | sort +0rn >> $outname

printf "\noutput stored as file: $outname\n"