What is %f in the for loop command?

Question

From this example right here. https://learn.microsoft.com/en-us/windows-server/administration/windows-commands/for#additional-references

for %f in (*.doc *.txt) do type %f

In the preceding example, each file that has the .doc or .txt extension in the current directory is substituted for the %f variable until the contents of every file are displayed. To use this command in a batch file, replace every occurrence of %f with %%f. Otherwise, the variable is ignored and an error message is displayed.

Are these different from variables in this example?

https://www.tutorialspoint.com/batch_script/batch_script_variables.htm

set message=Hello World 
echo %message%

What are these called? How do I manipulate them?

`%var%` is an "environment variable". It's valid anywhere ("global") until you explicitly destroy it (by undefining it or by `endlocal`, if it was defined after a `setlocal`). `%f` is a "for-variable" or "loop-variable" (I also heard the term "Metavariable"). It's valid only within the `for` loop and has no meaning after the `for` loop ends. Environment variables are manipulated with the `set` command (see `set /?`), for for-variables, there are "modifiers" (see `for /?`) — Stephan, May 19 '20 at 10:55
@Stephan How does the for variable work though? Is there a difference between %f and %g? Is it something I can manipulate? Is there a page that I can read more on? — PredictableBeaco, May 19 '20 at 11:00
well, there is `for /?`, but you can also visit [SS64](https://ss64.com/nt/) (look for the three links that start with `FOR`). It's better readable and even a bit more descriptive. You can roughly compare it with the runtime variables in other languages (`for $x = 1 to 5 do`). EDIT: Npocmakas answer summarizes it very well. — Stephan, May 19 '20 at 11:07

npocmaka · Accepted Answer · 2020-05-19T14:41:51.763

in batch scripting slang it is called for loop token and the example above will work only in the command prompt. For a batch file you'll need double %.

These tokens changes their values on each iteration of the for loop. Example (this can be executed in the command prompt):

for %a in (1 2) do @echo %a

this will have two iterations - in the first the value if the %%a token it will be 1 and on the seconds 2.

You can use for loops to read files (with /f switch and no quotes) ,to iterate files (with no switch) or directories (with /d switch), iterate through strings (again without switch but using wild cards in strings is not possible) to read files (with /f and no quotes), or process a string (again with /f).

you can also split the value of each iteration with "delims" option and then you'll need more consecutive letters :

for /f "tokens=1,2 delims=-" %a in ("1-2-3") do @echo %a:%b

this will split the string in the quotes by - and will take the first and the second part accessible by the %a and %b tokens.

What is %f in the for loop command?

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