Iterating over items
The
for %%a in (itemOne itemTwo itemThree) do … construct allows to iterate over the items within the parentheses. For each item, the text of the item is assigned to the single letter (!)
variable after the
for and then the statement after the
do executed.
If multiple statements are to be executed, they need to be enclosed within parentheses.
The following example has two loops where the two variables
%%a and
%%b are iterated from
0 to
f. Then, these variables are used to
set the console's color. After the console's colors were changed,
timeout.exe is invoked to sleep for a second.
Finally, when all 256 color combinations were iterated over, the whole process starts again (using the
goto statement.
@echo off
setlocal
set digits=0 1 2 3 4 5 6 7 8 9 a b c d e f
:doAgain
for %%a in (%digits%) do (
for %%b in (%digits%) do (
color %%a%%b
timeout /t 1 > nul
)
)
goto doAgain
Number of percent signs in a batch file and in the command line
If the
for command is used in a
batch file, the looping-variable needs to percent signs (for example
%%X) On the other hand, if the
for command is directly entered into the
cmd.exe prompt, only one percent sign is needed (for example
%X).