I have a file containing a list of several occurrences of line

```none
output = filename
output = filename
output = filename
output = filename

```

I also have a list of chronological filenames in a txt file which I would like to use to replace the occurrence `filename` in the order below

```none
2d_slv_Nx.19800111.SUB.nc
2d_slv_Nx.19800213.SUB.nc
2d_slv_Nx.19800322.SUB.nc
2d_slv_Nx.19800510.SUB.nc

```

I would like the following output 

```none
output = 2d_slv_Nx.19800111.SUB.nc
output = 2d_slv_Nx.19800213.SUB.nc
output = 2d_slv_Nx.19800322.SUB.nc
output = 2d_slv_Nx.19800510.SUB.nc

```