Remplacer des lignes par d'autres avec sed

[tmpfs]$ cat -n plop
     1  Method_phasefilt: goldstein: size, alpha, overlap: 32 0.9 11
     2  1D Smoothing kernel for |spectrum|: 0.111111 0.222222 0.333333 0.222222 0.111111
     3  Input_ diff
     4  Data_output_ diff.filt
     5  Data_output_format: complex_real4
     6  First_line (w.r.t. original_master): 3500
     7  Last_line (w.r.t. original_master): 4711
     8  First_pixel (w.r.t. original_master): 2844
     9  Last_pixel (w.r.t. original_master): 4100
    10  Multilookfactor_azimuth_direction: 5
    11  Multilookfactor_range_direction: 1
    12  Number of lines (multilooked): 1599
    13  Number of pixels (multilooked): 1177
    14  **********************************************
    15  Method: schwabisch
    16  Data_output_ demradar
    17  Data_output_format: real4
    18  First_line (w.r.t. original_master): 8400
    19  Last_line (w.r.t. original_master): 16634
    20  First_pixel (w.r.t. original_master): 2792
    21  Last_pixel (w.r.t. original_master): 3969
    22  Multilookfactor_azimuth_direction: 5
    23  Multilookfactor_range_direction: 1
    24  Ellipsoid (name,a,b): WGS84 6.378137e+06 6.3567523e+06

[tmpfs]$ sed -n '18,21 p' plop > tmp

[tmpfs]$ cat tmp
First_line (w.r.t. original_master): 8400
Last_line (w.r.t. original_master): 16634
First_pixel (w.r.t. original_master): 2792
Last_pixel (w.r.t. original_master): 3969

[tmpfs]$ sed '6,9 {:z;N; 9! bz; s/^.*$/cat tmp/e}' plop
Method_phasefilt: goldstein: size, alpha, overlap: 32 0.9 11
1D Smoothing kernel for |spectrum|: 0.111111 0.222222 0.333333 0.222222 0.111111
Input_ diff
Data_output_ diff.filt
Data_output_format: complex_real4
First_line (w.r.t. original_master): 8400
Last_line (w.r.t. original_master): 16634
First_pixel (w.r.t. original_master): 2792
Last_pixel (w.r.t. original_master): 3969
Multilookfactor_azimuth_direction: 5
Multilookfactor_range_direction: 1
Number of lines (multilooked): 1599
Number of pixels (multilooked): 1177
**********************************************
Method: schwabisch
Data_output_ demradar
Data_output_format: real4
First_line (w.r.t. original_master): 8400
Last_line (w.r.t. original_master): 16634
First_pixel (w.r.t. original_master): 2792
Last_pixel (w.r.t. original_master): 3969
Multilookfactor_azimuth_direction: 5
Multilookfactor_range_direction: 1
Ellipsoid (name,a,b): WGS84 6.378137e+06 6.3567523e+06

[tmpfs]$