added Toby's version of column chooser script

linux_intermediate/exercise_files/columnchooser_v2.sh

+#! /usr/bin/bash
+USAGE="columnchooser_v2.sh FILE COLNAME [COLNAME [...]]"
+# AUTHOR: Toby Hodges (toby.hodges@embl.de)
+
+if [ $# -lt 2 ]
+then
+    echo "USAGE: $USAGE"
+    exit 1
+fi
+
+file=$1
+shift
+cols=$@
+
+read -a headers <<< `head -n1 $file`
+numfields=${#headers[@]}
+declare -a outfields=()
+declare -i matchnum=0
+unmatched=""
+
+for col in ${cols[@]}
+do
+    matched=0
+    for colnum in $(seq $numfields)
+    do
+        if [ ${headers[$colnum-1]} = $col ]
+        then
+            outfields[$matchnum]="\$$colnum"
+            matchnum=$(($matchnum+1))
+            matched=1
+        fi
+    done
+    if [ $matched = 0 ]
+    then
+        unmatched="$unmatched $col"
+    fi
+done
+if [ $unmatched != "" ]
+then
+    echo "Sorry, no column(s) named $unmatched" 1>&2 
+fi
+awkfields=$(IFS=, ; echo "${outfields[*]}")
+awk "{ print $awkfields }" $file
+exit 0