Shell Programming and Scripting

pat1=
while read line; do
    case "$line" in
        pattern1)
            pat1="$line"
            ;;
        pattern2)
            if [ -n "$pat1" ]; then
                echo -e "Pattern 1: \"$pat1\"\nPattern 2: \"$line\"\n"
            fi
            pat1=
            ;;
    esac
done < file

foo
data 1
data 2
bar
data 10
data 20
foo
data 3
data 4
foo
data 5  should not print
data 6  should not print
bar
data 30
data 40

gzip -dc your-file-name | awk '
        BEGIN {
                seen1 = 0;         # state flags -- what section we last captured
                seen2 = 1;
                snarf = 0;          # don't assume pattern1 is first
        }

        /foo/   {                       # assume that pattern1/2 isnt in the data
                if( seen2 )             # weve seen pattern 2; ok to snarf data from this section
                        snarf = 1;      # ok to print data
                        # add print if you want pattern line printed
                else
                        snarf = 0;      # consecutive occurance of pattern 1, snarfing not allowed
                seen2 = 0;            # invert state to prevent printing consec foo section 
                seen1 = 1;
                next;                  
        }

        /bar/   {
                if( seen1 )           # not a consecutive pattern2 section 
                        snarf = 1;    # ok to snarf
                        # add print if you want pattern line printed
                else
                        snarf = 0;
                seen1 = 0;           # invert state to prevent printing consecutive bar section 
                seen2 = 1
                next;
        }

        snarf > 0 { print; }          # if ok to snarf, print the data record
'

data 1 
data 2
data 10
data 20
data 3
data 4 
data 30
data 40