Adding tabs to non delimited text file with empty and variable length columns - parsing

Question

I have a non-delimited text file and want to parse it to add tabs at specific spots to delimit columns. The columns are sometimes empty or vary in length, which is why I need to add tabs to those specific spots. I had found the answer to this once a couple of years ago on the net using batch, but now can't find it or the code. I already have the following code to replace more than 2 spaces in the file, but this doesn't account for when the columns are empty.
gc $FileToOpen | % { $_ -replace ' +',"`t" } | set-content $FileToSave
So, I need to read each line, but be able to only read a portion (certain number of characters) of it and add the tabs after each portion to itself.
Here is a sample of the data file, the top row is the header and the data rows have no blank lines in between them:
MRUN Number Name X Exception Reason Data CDM# Quantity D.O.S
000000 00000000 Name W MODIFIER CANNOT BE FILED WITHOUT 08/13/2015 0000000 0 08/13/2015
000000 00000000 Name W MODIFIER CANNOT BE FILED WITHOUT 0000000 0 08/13/2015
The second data row is missing Data.
Using Ansgar's answer, my code that does find empty fields:
gc $FileToOpen |
? { $_ -match '^(.{8})(.{12})(.{20})(.{3})(.{34})(.{62})(.{10})(.{22})(.{10})$' } |
% { "{0}`t{1}`t{2}`t{3}`t{4}`t{5}`t{6}`t{7}`t{8}" -f $matches[1].Trim(), $matches[2].Trim(), $matches[3].Trim(), $matches[4].Trim(), $matches[5].Trim(), $matches[6].Trim(), $matches[7].Trim(), $matches[8].Trim(), $matches[9].Trim() } |
Set-Content $FileToSave
Thanks for your patience Ansgar, I know I tried it! I really do appreciate the help!

Answer 1

Since you seem to have an input file with fixed-width columns, you should probably use a regular expression for transforming the input into a tab-delimited format.
Assume the following input file:
A B C
foo 13 22
bar 4 17
baz 142 23
The file has 3 columns. The first column is 6 characters wide, the other two columns 4 characters each.
The transformation could be done with a regular expression like this:
Get-Content 'C:\path\to\input.txt' |
? { $_ -match '^(.{6})(.{4})(.{4})$' } |
% { "{0}`t{1}`t{2}" -f $matches[1].Trim(), $matches[2].Trim(), $matches[3].Trim() } |
Set-Content 'C:\path\to\output.txt'
The regular expression defines the columns by character count and captures them in groups (parentheses). The groups can then be accessed as the indexes 1 and above of the resulting $matches collection. Trimming removes the leading/trailing whitespace. The format operator (-f) then inserts the trimmed values into the tab-separated format string.
If the last column has a variable width (because its values are aligned to the left and don't have trailing spaces) you may need to change the regular expression to ^(.{6})(.{4})(.{,4})$ to take care of that. The quantifier {,4} (or {0,4}) means up to four times the preceding expression.