Question: The Openssh ssh and scp command provied an `-i` command line option to specify the path to the RSA/DSA key to be used for authentication.

Looking at the sftp man pages I was not able to find a way to specify the RSA/DSA key.

I am looking for a way to do initiate an sftp session that will use a specified RSA/DSA key, and not the ~/.ssh/id\_{dsa,rsa} keys.

I tried OpenSSH sftp client on Linux...but it should have the same options on other platforms.

Answer: 
One potential option is to use `sftp -oIdentityFile=/path/to/private/keyfile`. Need more info to say whether that will work for you. Seems to work under Mac/Linux.
You can simply use the `-i` argument for your sftp or ssh command.

```
sftp -i /path/to/private/keyfile ...

```

If the -i option is not available, you can use the -o option with a syntax like:

```
sftp -oIdentityFile=/path/to/private/keyfile ...

```