How to know last commands run successfully?

hack3rcon · 08-09-2016, 12:50 AM

Hello.
I know that with the "echo $?" I can understand that the last command run successfully or not but how about other commands? For example, I run a command on a remote server via SSH and execute a "dd" command and close my terminal and do another SSH and run "ls" command but "echo $?" show me the result of "ls" command not "dd" command. How can I understand the result of "dd" command?

Thank you.

hazel · 08-09-2016, 01:18 AM

One way would be to keep a log file and follow each command with a conditional echo to that file.

Code:

if dd if=infile of=outfile bs=blocks; then
 echo "dd ran successfully" >> logfile
else echo "dd failed" >> logfile
fi

After all, that's basically how the init scripts do it.

Turbocapitalist · 08-09-2016, 02:07 AM

You have to look for the exit code for "dd" directly. You can do that on the remote host before logging out of the server. Or, if running just a single program or script in an automated fashion, the SSH client will pass the exit code of that program or script. It will also pass the exit code of the last program or script run before "exit". So if you connect with "ssh", run "dd", and then do nothing else before exit, then you can see the exit code of "dd" with $? on the local system.

Code:

ssh server.example.com /bin/true
echo $?
ssh server.example.com /bin/false
echo $?

malekmustaq · 08-09-2016, 02:59 AM

Quote:

For example, I run a command on a remote server via SSH and execute a "dd" command and close my terminal and do another SSH and run "ls" command but "echo $?" show me the result of "ls" command not "dd" command. How can I understand the result of "dd" command?

By recording a transcript of all activities, outputs and command returns made or transpired in the console. To do that, after opening the console/tty you will enter the command--

Code:

script mytranscriptfile1.txt

then you may now proceed to issue commands whatever you do, ssh, dd, ls, vi, etc. After you do that console session you may check and review what returns echoed by the commands as they ran.

Code:

cat mytranscriptfile1.txt

there you can find out whether the commands went good < 0 > or went error < 1 >. You will read the record even if you were not around. Just do not exit from the console. Should you have exited or quit from script CTL+D just redo the pre-pending of "script" anew.

Hope that helps.

Good luck and enjoy.

m.m.

sundialsvcs · 08-09-2016, 08:58 AM

By tradition, Unix/Linux programs have two "standard outputs": STDOUT, which is for "normal" output, and STDERR, which is for "error" (or "status message") output.

Although normally both of these output streams are displayed to the console and intermingled there, you can redirect them separately. For instance, the following command discards the error-output of the foobar command, by directing it to "the bit-bucket" (/dev/null, while sending the standard-output to the disk-file bletch:

Code:

 foobar >bletch 2>/dev/null

If you need to determine whether a command worked, you can test the command's exit-code for zero. (Zero means "success.") If you need details about why it [didn't ...] work, you must capture and parse the command's standard-error output.

hack3rcon · 08-09-2016, 09:50 AM

Just "script" exist? I guess a program must be exist for run command in different terminal and switch between them via PID.

pan64 · 08-09-2016, 10:44 AM

I do not understand your last post at all.
To the original question see man ssh, exit status:

Code:

ssh exits with the exit status of the remote command or with 255 if an error occurred.

Therefore the first ssh will return the status of ls, the second the status of dd.
You can also save the exit status by:

Code:

ssh <some command>
RC=$?
some other commands
use $RC (if you want)

malekmustaq · 08-09-2016, 10:22 PM

Quote:

Originally Posted by hack3rcon

Just "script" exist? I guess a program must be exist for run command in different terminal and switch between them via PID.

I forgot the basic clue, I am sorry. Just check the command and understand further:

Code:

 man script

The transcript runs in the background spawned from the console. If you want to run another transcript in separate console you may redo the method in the newly opened console.

Goodluck and enjoy!

m.m.

chrism01 · 08-10-2016, 03:03 AM

In short you have to collect the $? status immediately after each cmd, pref in separate vars if you intend to use those values later.

hack3rcon · 08-13-2016, 04:35 AM

I guess a program with the name "screen" can do it