用于循环变量扩展的Windows批处理脚本不起作用

Question

I am following this tutorial on windows script arrays and for loops. The examples are not working, tested on both windows 7 and 10.

Batch script tutorial

When I run the following for loop:

:: @echo off 
set list = 1 2 3 4 
(for %%a in (%list%) do ( 
    echo %%a 
))

I get the following output:

set list = 1 2 3 4
(for %a in ((null)) do (echo %a  ) )

The content of the list varialble is not printed in the for loop. I was expecting to get

1
2
3
4

Any ideas?

Answer 1

For info on using basic batch commands like SET, see SS64 great info source. In your case, as was commented above, the expanded variable name %list % must include space if present in its definition. If that space is not required in the variable definition, just remove it in the SET statement.

Spaces between array variable values list don't represent any problem, and can be quite handy in many example applications, in particular FOR loops, as they allow tokens use for finding the right values. This example works:

@echo off 
set "list= 1 2 3 4"
for %%a in (%list%) do ( 
    echo %%a 
)

For learning use of arrays in batch scripts, read Aacini 's answers:

• Create list or arrays in Windows Batch
• Arrays, linked lists and other data structures in cmd.exe (batch) script
• Arrays, structures and linked lists in Batch files

Using "array" terminology in batches is debated by some experts. See for example dbenham 's answer in DIR output into BAT array?