Shell Programming and Scripting

awk ' {
        a[++i]=$0
        l = i;
} END {
        for(j=l; j>=1; j--)
        {
                if(a[j] ~ /and/ && !f)
                {
                        sub("and",x,a[j]); f=1;
                }
        }
        for(i=1; i<=l; i++)
                print a[i];
}' filename

$ t="on a.id1 = b.id1 and
on a.id2 = b.id2 and
on a.id3 = b.id3 and"

$ echo "$t"
on a.id1 = b.id1 and
on a.id2 = b.id2 and
on a.id3 = b.id3 and

$ echo "$t"|sed '$ s:and::'
on a.id1 = b.id1 and
on a.id2 = b.id2 and
on a.id3 = b.id3

$ cat filename
on a.id1 = b.id1 and
on a.id2 = b.id2 and
on a.id3 = b.id3 and

$ awk ' {
>         a[++i]=$0
>         l = i;
> } END {
>         for(j=l; j>=1; j--)
>         {
>                 if(a[j] ~ /and/ && !f)
>                 {
>                         sub("and",x,a[j]); f=1;
>                 }
>         }
>         for (i=1;i<=l;i++)
>                 print a[i];
> }' filename
on a.id1 = b.id1 and
on a.id2 = b.id2 and
on a.id3 = b.id3

awk ' {a[++i]=$0; l=i } END { for(j=l; j>=1; j--) { if(a[j] ~ /and/ && !f) { sub("and",x,a[j]); f=1; } } for(i=1; i<=l; i++) print a[i]; }'