Command Prompt Search for files in a directory take the name of one random

问题

Inside a directory c:\configs I have files with various extensions including the extension .rac. I need a script for the Windows command prompt that looks inside c:\configs for the names of the files that end with the extension .rac, ignoring other extensions. Then of all the names that end with .rac extension the script must choose a random one and process it with the command c:\programs\submit.exe namerandom.rac.

For example, suppose that random .rac file is called mosaic.rac, then the script executes the command c:\programs\submit.exe mosaic.rac. Of course the mosaic.rac name changes each time the script is runs because it is a random selected from the all the .rac files found.

Anyone have an idea in how to do and that can put example code?

回答1:

To accomplish that, you may use the following...

Firstly, to get all .rac files, use the dir command. The /B switch specifies to output only a bare file list without any headers nor footers. If you want to search the given directory recursively, add the /S switch:

dir /B "C:\configs\*.rac"

Secondly, you need to count the number of returned .rac files. You can use a for /F loop (parsing the output of dir /B) together with set /A for that:

set /A COUNT=0
for /F "delims=| eol=|" %%L in (
  'dir /B "C:\configs\*.rac"'
) do (
  set /A COUNT+=1
)

Thirdly, you need to compute a random number in the applicable range. The built-in variable RANDOM retrieves a random number from 0 to 32767, so we need a little maths. The result will be a number from 0 to %COUNT% - 1:

set /A RNDNUM=%RANDOM%%%COUNT

Fourthly, you can use another for /F loop with the skip option to select a random file (we skip the previously calculated number RNDNUM of lines).
The if statement ensures that no skip option is provided in case the random number is 0.
The goto command ensures that only the selected file is passed to submit.exe. If you omitted it, every file after the selection would be passed over to submit.exe too, one after another:

if %RNDNUM% gtr 0 (
  set SKIP=skip=%RNDNUM%
) else (
  set SKIP=
)
for /F "%SKIP% delims=| eol=|" %%L in (
  'dir /B "C:\configs\*.rac"'
) do (
  start "" /WAIT "submit.exe" "%%~L"
  goto :CONTINUE
)
:CONTINUE

Put together those parts to get the final script.

Type each command and append /? in command prompt to get the respective help text displayed.

回答2:

@echo off
setlocal EnableDelayedExpansion & set n=0
for /f "delims=" %%a in ('dir /b /A-D "*.rac"') do (
set "f=%%a" & set "f[!n!]=!f!" & set /a "n+=1")
set /a c=%random% %% n
echo !f[%c%]!

Explanation:

Line #4: it make a pseudo array in f with n incremented by 1
Line #5: it take a random number between 0 and the total count of files called n with the help of: %random% modulo n

In this way, this creates a number of variables automatically according to their position then %random% %% n picks one.

You might as well picks some manually like this:

echo !f[0]! !f[1]! !f[2]! !f[3]! !f[4]! !f[5]! ...

来源：https://stackoverflow.com/questions/32682201/command-prompt-search-for-files-in-a-directory-take-the-name-of-one-random

标签

windows

batch-file

cmd