Read a text file that includes numbers and strings and edit it in different places

I have a text file that is something like the attached picture. I want to read this file and whenever I come to the line 67 my code will add lines like

67 and 68 and follows as,

67 *Nset, nset=node1, instance=Part-1-1

68 1

69 *Nset, nset=node2, instance=Part-1-1

70 2

71 *Nset, nset=node3, instance=Part-1-1

72 3

and onwards...

Basically it will add two lines after it counters the line 67th.

67

Answer 1

[Walter Roberson]

readlines() to get a string array. Index 1:66, then several entries with the new lines, then index 68:end. writelines() the results.

[MD MAHABUBUR ROHOMAN]

Thanks for your response. What if I just want to write a text file like the following,

*Nset, nset=node1, instance=Part-1-1

1

*Nset, nset=node2, instance=Part-1-1

2

....

...

..... and onwards?

[Walter Roberson]

nodenums = 1:3;
part1 = "*Nset, nset=node";
part2 = ", instance=Part-1-1";

output1 = part1 + nodenums.' + part2;
output2 = string(nodenums.');

output = reshape([output1, output2].', [], 1)

output = 6×1 string array
    "*Nset, nset=node1, instance=Part-1-1"
    "1"
    "*Nset, nset=node2, instance=Part-1-1"
    "2"
    "*Nset, nset=node3, instance=Part-1-1"
    "3"

filecontents = readlines(FILENAME);
newcontents = [filecontents(1:66); output; filecontents(68:end)];

writelines(newcontents, NEWFILENAME);