Leading Semicolon Comments a Line in CMD FOR /F

I wondered why the following CMD script was not processing some lines ...

for /f %a in (test.txt) do @echo %a

... with this sort of test where the semicolon is a field separator. All the lines were processed when the field separator is a space, tab or comma.

x;y;z
;y;z

When I ran the script, the echo command is only called for the first line. It turns out that, by default, for /f regards any line starting with a semicolon to be a comment and ignores it. It's similar to using:

for /f "eol=;" %a in (test.txt) do @echo %a

Note that the Microsoft documentation doesn't state the default for the eol keyword.

See Also

• For /f - Loop through text
• Microsoft Windows XP - For