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Under what circumstances should we use %a, and when should we use %i or %k, etc.?

Both "i" and "a" are among the 26 English letters. In FOR, they are both variables with no difference. Unless it's FOR /L, where "L" is different, it's an extended command.

Is it saying that for %a in (3.txt) do find "2008" %a and for %i in (3.txt) do find "2008" %i are the same?

for %a in (3.txt) do find "2008" %a and for %i in (3.txt) do find "2008" %i

They are the same

Sweat. It's just a variable. Custom - defined.

In ordinary applications of for, %a, %i, and %k are not essentially different. Only one variable is sufficient to refer to a group of files, directories, or number sequences, and multiple variable symbols will not appear simultaneously in the for statement.

But when parsing file groups using the /f parameter, the delims and tokens keywords in the "options" parameter define multiple groups of characters, and multiple variables must be used to represent them in sequence. So we often see multiple variable symbols in the for /f statement, and then there is a difference between using %a or %i.

First, let's look at a piece of help information about for /f variables:
"%i is specifically explained in the for statement, and %j and %k are specifically explained through the tokens= option. You can specify up to 26 symbols in a tokens= line, as long as you don't try to explain a variable higher than the letter 'z' or 'Z'. Remember that FOR variables are single letters, case-sensitive, and global; and at the same time, no more than 52 can be in use."

Here it is mentioned that only 26 symbols can be defined, that is, at most 26 variable symbols can appear in the for /f statement. If the first variable is defined as %a, the second is %b, and so on, the last one is %z, and the total number of variables is 26; while if the first variable is defined as %i, the second can only be %j, and the last one is still %z, but the number of definable variables is reduced by 8, leaving only 18.

The following example can intuitively show the difference:
If the format of the 3.txt file is as follows:
1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30
Then for /f "tokens=1-30 delims=," %a in (3.txt) do echo a%,%z will see 1,26, while for /f "tokens=1-30 delims=," %i in (3.txt) do echo i%,%z will see 1,18 (numbers after 18 cannot be defined).

[ Last edited by hizebra on 2007-10-11 at 05:53 PM ]

It is mentioned here that only 26 symbols can be defined, that is, at most 26 variable symbols can appear in the for /f statement.

There are definitely more than 26 symbols:

for /f "tokens=1,3,4" %+ in ("hello world batch fans") do @echo %+/%,/%-

What you said is really detailed

There is not much difference,
Just the DO front and back variables need to be consistent

Originally posted by lxmxn at 2008-1-6 00:48:


There are definitely more than 26 symbols:

for /f "tokens=1,3,4" %+ in ("hello world batch fans") do @echo %+/%,/%-

Is it according to the increasing order of ASCII codes?

There is not much difference. Just when using for /f, %a is used to receive the lower segment character and %b is used, and %i is used to receive with %j.

Of course it's the same.

The following is the introduction under the command prompt:

FOR %%variable IN (set) DO command [command-parameters]
%%variable specifies a single letter replaceable parameter.
(set) specifies one or a group of files. Wildcards can be used.
command specifies the command to be executed for each file.
command-parameters specifies parameters or command line switches for a specific command.

Can you explain the meaning of the code on the seventh floor? I can't understand it. Thanks!