Write output of base64 encode on a file to the same file?

Question

Using WSL2 (Ubuntu 20.04), I have a file, out.txt with the phrase password that I am encoding using base64:

$ echo password > out.txt
$ base64 out.txt
$ # returns cGFzc3dvcmQ=

I wanted to ask if there was some way to write the output of the base64 command back into its original file out.txt. When I try to do so currently (base64 out.txt > out.txt), I end up with a blank file. Piping the command's output into another file (base64 out.txt > oot.txt) works fine, but I'd prefer if I kept everything to the same file.

Trying to achieve this for the purpose of scripting a shell file with an sshpass command (yes, I know about keyless authentication and whatnot but unfortunately I don't have the ability to configure this on the server I'm connecting to) and would obviously rather not have the password in plaintext in my command history.

@TedLyngmo This will cause an infinite loop when the size of the file is larger than base64's buffer — that other guy, May 03 '22 at 21:46
This is probably the easiest: `echo "$(base64 out.txt)" >out.txt` — Cyrus, May 03 '22 at 22:01

score 2 · Answer 1 · answered May 03 '22 at 21:49

2

Use sponge, which (unlike simple pipe) buffers the entire input first before writing it to the given file.

base64 out.txt | sponge out.txt

answered May 03 '22 at 21:49

Piotr Henryk Dabrowski

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Write output of base64 encode on a file to the same file?

1 Answers1