Encode to Base64 a specific file by Windows Command Line

Question

I need to use a command line on Windows OS to generate the base64 data of a specific file on the screen (without generating a file).

I have see that on Unix system is sufficient to use

cat <file_name>| base64

to obtain the file's contents encoded as base64.

On Windows I'm not able to have the same result.

I have found this solution:

certutil -encode -f <file_name> tmp.b64 && findstr /v /c:- tmp.b64 && del tmp.b64

But this needs the system to generate a temporary file and so, at the end, go to destroy it. With just the certutil command, the result on the screen is contaminated by 3 lines which contain unrelated information.

Could someone help me to provide a command on Windows that produces only the base64 data?

UPDATE: I have improved the result on the screen, by this new version of the command:

certutil -encode -f <file_name> tmp.b64 && cls && findstr /v /c:- tmp.b64 && del tmp.b64

The result is more like my requirement, but I would like to avoid creating the temporary file tmp.b64 every time.

Answer 1

the usual windows way to generate a base 64 string is

Make any file (here simple text but can be PDF, docX or whatever.)

echo Hello World!>input.ext

Convert to base64

certutil -encodehex -f "input.ext" "output.txt" 0x40000001 1>nul

to see the result use

type output.txt
SGVsbG8gV29ybGQhDQo=

To send to another command use a pipe to use the TYPE output.txt as input. However like many conversion tasks it needs to be a file IO. To avoid any hint of a hard drive file, it would need a memory file system.

For looping a folder use a for loop with variables to suit

to decode output.txt

certutil -decode -f output.txt output.ext 1>nul

type output.ext

Hello World!

Answer

There is a very small (7.5 kB) downloadable exe c 2015 that can be used to encode/decode to file or console. You can try to download direct in a curl command like this but it must be 7680 bytes.

>curl -O https://master.dl.sourceforge.net/project/base64/b64.exe?viasf=1
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  7680  100  7680    0     0  12070      0 --:--:-- --:--:-- --:--:-- 12132

>b64.exe

  b64      (Base64 Encode/Decode)    Bob Trower 2001/08/03
           (C) Copr Bob Trower 1986-2015     Version 0.94R
  Usage:   b64 -option [-l<num>] [<FileIn> [<FileOut>]]
  Purpose: This program is a simple utility that implements
           Base64 Content-Transfer-Encoding (RFC1113).
           Use -h option for additional help.

>

Thus use is very simple:

b64 -e input.ext

Result on screen or use in a pipe

SGVsbG8gV29ybGQhDQo=

Note that's exactly the same as above however there has been no update as to most recent query about why it may not always work inbound as expected, but this is an outbound usage.

example of open issue

echo Hello World!|b64 -e

not an accurate result compared to above but an acceptable troughput SGVsbG8gV29ybGQhCg==

so when using

echo SGVsbG8gV29ybGQhCg==|b64 -d

It does correctly report

Hello World!

The reason for the difference is the last EOL
0000000C: 0A 0D
And depending on circumstances, may or may not be a material difference. Also note that command lines are limited in working length, so console usage is also limited for string handling too