How to get output in a specified format

Question

In Fortran, we can easily get the stardard and easy output format. Now, we only focus on the Integer output. See here How to realize this kind of output as formatted text file using Mathematica ? (Then it can be read in Fortran easily).Take a simple example, I have a list,

   list=Table[(i + j) i (i - j), {i, 1, 2}, {j, 1, 22}];

I want to get the output data in a text file and

1. Every integer should be printed with 6 positions. (It is I6 in Fortran).

2. The maximum line length in the text file should be limited to 120.

   

Answer 1

data = Table[(i + j) i (i - j), {i, 1, 2}, {j, 1, 22}]; 

The first step is to define a function to break up each row in the data into lines not exceeded the specified maximum line length.

prep[row_, fieldWidth_, lineLength_] :=
  Module[{items = Floor[lineLength/fieldWidth]}, 
    Partition[row, items, items, 1, {}]]

The second step is to do the breaking. I have shorten the lines to 80 characters for better looking output to show here.

lines = Flatten[prep[#, 6, 80] & /@ data, 1];

The third step is to make the strings

output = 
  StringJoin @@@ 
    Map[StringTake[StringJoin["     ", ToString@#], -6] &, lines, {2}]

The final step is to export the strings. I use ExportString for demonstration.

ExportString[output, "Text"]

You can use something similar to

Export["~/Desktop/test.txt", output, "Text"]

to put the strings into a disk file.

Update

As suggested by SjoerdC.deVries in a comment,

output = 
  StringJoin @@@ 
    Map[ToString[NumberForm[#, 6, NumberPadding -> " "]] &, lines, {2}];

is an alternative way to make the strings.