format in TCL in not working correctly - format

Question

format in TCL in not working correctly,I am trying to format some text and writing them in a file and then sending that file as a mail to user.
I am seeing that format is correct in Linux but when mail comes to user then format is not proper.
code-
puts [format {%-50s%-170s%-50s%-50s} "Test_Id" "Test_Description" "Test_Ran_Count" "Test_Result"]
puts [format {%-50s%-170s%-50s%-50s} $test_id1 "$mail_desc1" $loop_count $test_result]
puts [format {%-50s%-170s%-50s%-50s} $test_id "$mail_desc" $loop_count $test_result]
output-
Test_Id Test_Description Test_Ran_Count Test_Result
test_id_1 To execute - test_id_1 10 PASS
test_id_2 To execute - test_id_2 10 PASS
here if test_id_2 is big then entire format is shifting,as per format behavior if test_id is less then 50 char then it should not shift other column as I am giving %-50s for test_id.

Answer 1

Format fields (which Tcl borrows from C's sprintf() with very few changes) are a bit tricky. When you use %50s (or %-50s — the - just affects alignment) you are setting a minimum field width. To set a maximum field width, you might use %.50s. Or, more likely in your case, you'll set minimum, maximum and alignment: %-50.50s.
Demonstrating with some narrower fields and simple strings of different lengths:
foreach str {abc defgh ijklmnop} {
puts [format ">%-5.5s< |%-5s| /%-.5s/" $str $str $str]
}
Which produces this output:
>abc < |abc | /abc/
>defgh< |defgh| /defgh/
>ijklm< |ijklmnop| /ijklm/
As you can see, left aligned, completely fixed width requires giving %-N.Ns (for some N).