Skipping last empty line of WMIC command output in batch

问题

I am trying to format the output of a command in JSON as such:

echo "patches" : {
set patches="wmic qfe get HotfixID"
for /f "skip=1" %%i in (' %patches% ') do (
    set /a count=count+1
    call echo "!count!" : "%%i",
)
echo }

Everything is fine until I hit the end of the list of patches where it reads the line after the last patch and then prints "".

How can I make it stop when it is supposed to?

If possible, I would like to avoid using text files.

回答1:

Inside the for /f loop, place another one:

for /f "skip=1" %%i in ('%patches%') do for /f "delims=" %%j in ("%%i") do (
    rem // use `%%j` in the loop body
)

The wmic command returns Unicode output. Since for /f is not perfect for handling such, it produces artefacts like orphaned carriage-returns (CR), leading to the effect you encounter (the last line does not appear empty to your for /f %%i loop as it contains such a CR; remember that for /f skips lines that are really empty). Placing another for /f loop inside and hence double-processing each item removes such artefacts.

Here is the fixed script:

echo "patches" : {
set "patches=wmic qfe get HotfixID"
for /f "skip=1" %%i in ('%patches%') do for /f "delims=" %%j in ("%%i") do (
    set /a count=count+1
    echo "!count!" : "%%j",
)
echo }

Since I did not get the purpose of the call command, I simply removed it.

The double-parsing method is actually credited to dbenham -- see his answer to Why is the FOR /f loop in this batch script evaluating a blank line? and also his external article WMIC and FOR /F : A fix for the trailing <CR> problem.

回答2: