#!/bin/sh
#
# Search news articles for a regular expression, and display matching ones
#

[ $# -lt 2 ] && { echo "usage: sn groups pattern" >&2; exit 1; }

readnews -i -p -n "$1" | nawk '
function pbuf() { for (i = 0; i < n; i++) print buf[i] }
BEGIN { m = n = 0 }
/^-----------/ { hs = $0; next }
/^Newsgroup / && hs {
    getline tmp
    if (tmp ~ /^-----------/) getline
    else {if (n) {buf[n++] = hs; buf[n++] = $0; buf[n++] = tmp}}
    hs = ""; next
}
/^Article [0-9]+ of [0-9]+ \([^ ]+\) / {
    if (m) pbuf()
    m = n = 0; buf[n++] = $0; next
}
/'"$2"'/ { if (n) m = 1 }
{ if (n) buf[n++] = $0; hs = "" }
END { if (m) pbuf() }' | ${PAGER:-more}
.