for g in $master_ext_name_ddn; do

$VALOR=grep "$ruta" K?????$MES_ANTERIOR.rep | grep "$h"

done

for g in $master_ext_name_ddn; do

  $VALOR=$(grep "$ruta" K?????$MES_ANTERIOR.rep | grep "$h")

  if [ "$VALOR" == "" ] # Cuando no hay match la variable $VALOR estará vacía
  then
    echo "no hay match"
  else
    echo "Match!"
  fi

done