qrscan: use new one shot scanning mode

krebs/5pkgs/simple/qrscan.nix

@@ -1,27 +1,7 @@
-{ coreutils, gnused, writeDashBin, zbar }:
+{ pkgs }:
 
-writeDashBin "qrscan" ''
+pkgs.writeDashBin "qrscan" ''
   set -efu
 
-  tmpdir=$(${coreutils}/bin/mktemp --tmpdir -d qrscan.XXXXXXXX)
-  codefile=$tmpdir/code
-
-  cleanup() {
-    ${coreutils}/bin/rm "$codefile"
-    ${coreutils}/bin/rmdir "$tmpdir"
-  }
-
-  ${coreutils}/bin/mkfifo "$codefile"
-
-  ${zbar}/bin/zbarcam > "$codefile" &
-  zbarcampid=$!
-
-  exec < "$codefile"
-  while read -r code; do
-    code=$(printf %s "$code" | ${gnused}/bin/sed -n 's/^QR-Code://p')
-    if test -n "$code"; then
-      ${coreutils}/bin/kill "$zbarcampid"
-      echo "$code"
-    fi
-  done
+  ${pkgs.zbar}/bin/zbarcam -1 | ${pkgs.gnused}/bin/sed -n 's/^QR-Code://p'
 ''