Re: Getting error string from a failed ssh command

[Jakub Jelen <jjelen@xxxxxxxxxx>]

On 10/4/22 00:36, Norm Green wrote:
> Hello libssh list,
>
> If I run a command over ssh that fails from the Linux command line:
>
> normg@moop>ssh hood foo
> bash: foo: command not found
> normg@moop>echo $?
> 127
>
>
> I get an error string ("bash: foo: command not found") and an error code 
> (127). For example:
> My question is how to do the equivalent with libssh ?
> If I do this after opening a session and a channel:
>
> int rc = ssh_channel_request_exec(sshChannel, "foo");
> int bytesReady = ssh_channel_poll_timeout(sshChannel, timeout, FALSE);
>
> returns -127 and:
>
> int numRead = ssh_channel_read_timeout(sshChannel,
>                               resultBuffer.nextWriteByte(),
>                               (int) resultBuffer.bytesFree(),
>                               0, // timeout: block in poll, not here
>                               0);
>
> returns 0, so I don't get the error string back from libssh.
> How can I get the error string result from the failed command using 
> libssh ?

I think you need to set the `is_stderr` argument of the 
`ssh_channel_read_timeout()` to true to get this message as it will most 
likely be on the standard error instead of standard output you are querying.

Regards,
--
Jakub Jelen
Crypto Team, Security Engineering
Red Hat, Inc.