I am trying to call ssh-keygen
using a variable through bash
as an input instead of a file to get a fingerprint of a public key. I am aware that I could use a temp file to get around this issue, but for reasons out of scope of this question, I do not want to.
This method does not work as it says the key file is invalid (it's correct for sure)
echo $pubkey | ssh-keygen -lf /dev/stdin
This does work, but is not using a variable, rather a file.
ssh-keygen -lf alpha.pub
This does work, but is not using a variable, rather a redirected file.
ssh-keygen -lf /dev/stdin < alpha.pub
This does not work because I get an ambiguous redirect
ssh-keygen -lf /dev/stdin < $(echo $pubkey)
I would appreciate some insight as to how to get ssh-keygen to read from a variable with a public key and if possible, an explanation as to why the redirects aren't doing what I think they should be doing. In specific why the |
behaves differently than the <
and why the third example is an ambiguous redirect
. I searched online but many of the redirect tutorials didn't seem to answer my questions.
echo $pubkey | ssh-keygen -lf /dev/stdin
/dev/stdin is not a public key file.
/dev/stdin is actually a unix pipe, not a regular file, so ssh-keygen fails to open the file
ssh-keygen -lf /dev/stdin <<<$key
1024 92:6a:3f:5c:1f:78:.....
/dev/stdin refers to a regular file, created by using a bash heredoc. You can verify this:
# ls -l /dev/stdin <<<$pubkey
lrwxrwxrwx 1 root root 15 Feb 11 08:07 /dev/stdin -> /proc/self/fd/0
# ls -l /proc/self/fd/0 <<<$pubkey
lr-x------ 1 juergen juergen 64 Apr 14 13:31 /proc/self/fd/0 -> /tmp/sh-thd-1271250023 (deleted)