I'm trying to understand how scp works "under the hood".
The only reference I found that seem to explain how things work is a blog post on the Oracle website, through web archive.
Well, there, we can find a few examples, for instance:
{ echo D0755 0 testdir; echo C0644 6 test 123;
printf "hello\\n"; echo E; } | scp -rqt /tmp
While it does create /tmp/testdir/test 123 with the right content, it actually exit 1. We can get more info by removing the -q flag:
$ { echo D0755 0 testdir; echo C0644 6 test 123;
printf "hello\\n"; echo E; } | scp -tr /tmp
test 123 0% 0 0.0KB/s --:-- ETA
$ echo $?
1
So, we can see, it exits 0 and the progress is never updated.
My question is: why?
At first I thought it was because the terminal is not a SSH session, but then I actually tried to do it using golang.org/x/crypto/ssh, and I get the same results.
My guess is that both the terminal and my implementation are missing something, I don't know what it is, though.
Any pointers?
OK, I figured it out!
Need to send a null byte after the file:
$ {
echo D0755 0 testdir;
echo C0644 6 test 123;
printf "hello\\n";
printf "\x00";
echo E;
} | scp -tr /tmp
test 123 100% 6 102.4KB/s 00:00
$ echo $?
0
Related
I have micro:bit attached to my laptop on which running Xubuntu 18.04.4 LTS.
After I attached micro:bit an icon appeares on XFCE4 Desktop which can
to use to mount this device to
/media/MyUserName/MICROBIT/
This way I can pair the device 'BBC micro:bit CMSIS-DAP' and my laptop
by using https://python.microbit.org/v/2.0 in my Google Chrome browser.
But in mu-editor I can't do this, can't use neither REPL, nor FILE
because I get this message box:
"Colud not find an attached device
Please make sure the device is plugged into this computer.
It must have a version of MicroPython (or CircuitPython) flashed onto it
before the REPL will work.
Finally, press the device's reset button and wait a few seconds before
trying again."
$ lsusb
ID 0d28:0204 NXP LPC1768
This line above is for the micro:bit attached.
$ ls /dev/ | grep tty
In the output of the command above there is not a /dev/ttyACM0
or other ACM* device out there.
Why is not there such a device /dev/ttyACM* out there?
I suspect mu-editor does not find the device because there is no such
device /dev/ttyACM* out there.
How can I solve the problem for mu-editor?
I use Debian Linux. There are two things you may need to do:
I had to update the firmware on the micro:bits recently to be able to continue using the mu-editor. The instructions on how to do this are here:
[https://microbit.org/get-started/user-guide/firmware/]
Mount the micro:bit. This can be done by double clicking on the 'MICROBIT' shown in e.g. Nautilus, or from the command line using udisksctl. Please find a bash script below called microbit_mount.sh which uses udisksctl to mount and dismount a microbit. To mount a microbit, use the command:
microbit_mount.sh mount
To unmount a microbit, use
microbit_mount.sh unmount
I have these commands aliased to mm amd md.The microbit will appear in /media/MICROBIT. You may need to remount the microbit after each flash.
#!/bin/bash
# microbit_mount.sh
# mount and unmount microbit
# modified from https://askubuntu.com/questions/342188/how-to-auto-mount-from-command-line
BASEPATH="/media/$(whoami)/"
MICRO="MICROBIT"
if [ $# -eq 0 ]
then
echo "no argument supplied, use 'mount' or 'unmount'"
exit 1
fi
if [ $1 == "--help" ]
then
echo "mounts or unmounts a BBC micro:bit"
echo "args: mount - mount the microbit, unmout - unmount the microbit"
fi
# how many MICRO found in udisksctl dump
RESULTS=$(udisksctl dump | grep IdLabel | grep -c -i $MICRO)
case "$RESULTS" in
0 ) echo "no $MICRO found in 'udkisksctl dump'"
exit 0
;;
1 ) DEVICELABEL=$(udisksctl dump | grep IdLabel | grep -i $MICRO | cut -d ":" -f 2 | sed 's/^[ \t]*//')
DEVICE=$(udisksctl dump | grep -i "IdLabel: \+$DEVICELABEL" -B 12 | grep " Device:" | cut -d ":" -f 2 | sed 's/^[ \t]*//')
DEVICEPATH="$BASEPATH""$DEVICELABEL"
echo "found one $MICRO, device: $DEVICE"
if [[ -z $(mount | grep "$DEVICE") ]]
then
echo "$DEVICELABEL was unmounted"
if [ $1 == "mount" ]
then
udisksctl mount -b "$DEVICE"
exit 0
fi
else
echo "$DEVICELABEL was mounted"
if [ $1 == "unmount" ]
then
udisksctl unmount -b "$DEVICE"
exit 0
fi
fi
;;
* ) echo "more than one $MICRO found"
;;
esac
echo "exiting without doing anything"
I installed Xubuntu 20.04 and on this system mu-editor works in the Files mode and REPL mode with the attached micro:bit.
I have log file keep updating for 30 minutes and I implement script which will check that log file till it has "success" message written in it.So far I have implemented below.Any help or correction would be appreciated.
while [ "($cat R12TECH2.log | grep 'success')" != " " ]
do
echo "Please wait...devccm Adautoconfig is still running..."
sleep 5
done
echo "Status of devccm adautoconfig"
cat R12TECH2.log | grep 'success'
exit
Replace
while [ "($cat R12TECH2.log | grep 'success')" != " " ]
With:
while ! grep -q 'success' R12TECH2.log
The while statement does not require a [...] statement. It will work with any command that provides a satisfactory exit code. grep is one such command. Since we don't care about the output of the grep command, we use -q to silence it.
Grep and exit codes
Consider the test file:
$ cat R12TECH2.log
line 1
success
line 3
This grep command returns success (0):
$ grep -q 'success' R12TECH2.log; echo code=$?
code=0
We, however, want the while loop to run only if success is not in the file. Thus, provide a leading ! which tells the shell to negate the exit code:
$ ! grep -q 'success' R12TECH2.log; echo code=$?
code=1
I would like to modify one of my recent Bash aliases to forward errors. Here is the alias:
alias makecclip=
"make |& tee >(sed \"s,\x1B\[[0-9;]*[a-zA-Z],,g\" |
egrep \":[0-9]+:[0-9]+: error\" | cut -d : -f1,2,3 |
head -n 1 | xargs -0 echo -n | xclip -selection clipboard &&
xclip -selection clipboard -o)
This code displays the results of a C++ compilation, and then removes formatting and displays and adds to the clipboard the first error location (if there is any).
However, I would like to use this code like this:
makecclip && bin/someexecutablecreated
This though ruins the && operator, since it always runs bin/someexecutablecreated even when there is a compilation error present. How can I add modifications to the code to set the error flag, when the error list (the things saved to clipboard and echoed) is not empty?
You can address your issue by using the PIPESTATUS internal variable (this variable has other names in non-bash shells). This allows to have an history of exit statuses of commands passed by pipe.
You precised in the comments that you didn't use bash, but used zsh instead. As such, some of the syntax of my solution has to be changed, as they handle the PIPESTATUS variable differently.
In bash, you use ${PIPESTATUS[0]}, whereas you'll use ${pipestatus[1]} in zsh.
A first approach, using your existing alias, could be as follow :
makecclip && [ "${pipestatus[1]}" -eq "0" ] && echo "ok"
This runs the echo command only if "${pipestatus[1]}" is equal to 0 (no errors during make)
A more convenient solution would be to use a function instead of an alias for makecclip. In your ~/.bashrc file, you could write :
makecclip () {
make |& tee >(sed "s,\x1B\[[0-9;]*[a-zA-Z],,g" | egrep ":[0-9]+:[0-9]+: error" | cut -d : -f1,2,3 | head -n 1 | xargs -0 echo -n | xclip -selection clipboard && xclip -selection clipboard -o)
return "${pipestatus[1]}"
}
Now, makecclip && echo "ok" will work as expected.
Test cases :
#!/bin/zsh
#do not run this test if there is an existing makefile in your current directory
rm -f makefile
makecclip () {
make |& tee >(sed "s,\x1B\[[0-9;]*[a-zA-Z],,g" | egrep ":[0-9]+:[0-9]+: error" | cut -d : -f1,2,3 | head -n 1 | xargs -0 echo -n | xclip -selection clipboard && xclip -selection clipboard -o)
# this part is only present to check the pipestatus values during the tests.
# In the real function, I wrote 'return ${pipestatus[1]}' instead.
a=(${pipestatus[#]})
echo ${a[#]}
return ${a[1]}
}
echo "# no makefile"
makecclip && echo "ok"
echo -e "\n# empty makefile"
touch makefile
makecclip && echo "ok"
echo -e "\n# dummy makefile entry"
echo -e 'a:\n\t#echo "inside makefile"' > makefile
makecclip && echo "ok"
echo -e "\n# program with error makefile"
echo -e "int main(){error; return 0;}" > target.cc
echo -e 'a:\n\tgcc target.cc' > makefile
makecclip && echo "ok"
Output :
$ ./test.sh
# no makefile
make: *** No targets specified and no makefile found. Stop.
2 0
# empty makefile
make: *** No targets. Stop.
2 0
# dummy makefile entry
inside makefile
0 0
ok
# program with error
gcc target.cc
target.cc: In function ‘int main()’:
target.cc:1:12: error: ‘error’ was not declared in this scope
int main(){error; return 0;}
^
makefile:2: recipe for target 'a' failed
make: *** [a] Error 1
target.cc:1:12
2 0
I have a script in FreeBSD 10.1 release, it's purpose is to monitor another process and keep the process alive.
When I try to kill itself, it always fail.
I try killall [name | pid]; pkill -9 [name]; service watchtas stop, none of them work.
Below is my script, please advise the solution.
#!/bin/sh
. /etc/rc.subr
prog="Thin-Agent WatchDog"
TAS_BIN="/etc/supermicro/tas-freebsd.x86_64"
TAS_LOG="/etc/supermicro/tas_system_crush.log"
monitor=1
name="watchtas"
rcvar=${name}_enable
command=/etc/rc.d/{$name}
start_cmd="watchdog"
stop_cmd="stop_watching"
load_rc_config $name
recover_tas() {
$TAS_BIN -agent start-service
RETVAl=$?
return $RETVAL
}
stop_watching() {
monitor=0
}
watchdog() {
while [ $monitor == 1 ]
do
tas_count=`ps -x | grep tas-freebsd.x86_64 | grep -v grep | wc -l | sed 's/ *//g'`
if [ $tas_count -eq 0 ]; then
timestamp=`date`
echo "[$timestamp]TAS shutdown unexpectedly, restarting TAS now..." >> $TAS_LOG
echo $?
recover_tas
else
sleep 10
fi
done
}
run_rc_command "$1"
Your start-up script fails in a couple of respects. service watchtas start does not return to the command line because the daemon process does not detach. service watchtas stop does not work as required because the variable monitor is local to the executing script.
I would separate the start-up script and the watchdog code into separate files and use daemon(8) to monitor the watchdog.
The /usr/local/etc/rc.d start-up script would look like this:
#!/bin/sh
. /etc/rc.subr
name="watchtas"
rcvar=${name}_enable
pidfile="/var/run/${name}.pid"
command="/usr/sbin/daemon"
command_args="-c -f -P ${pidfile} -r /usr/local/sbin/${name}"
load_rc_config $name
run_rc_command "$1"
The /usr/local/sbin/watchtas watchdog code would look something like this:
#!/bin/sh
TAS_BIN="/etc/supermicro/tas-freebsd.x86_64"
TAS_LOG="/etc/supermicro/tas_system_crush.log"
recover_tas() {
$TAS_BIN -agent start-service
RETVAl=$?
return $RETVAL
}
while true
do
tas_count=`ps -x | grep tas-freebsd.x86_64 | grep -v grep | wc -l | sed 's/ *//g'`
if [ $tas_count -eq 0 ]; then
timestamp=`date`
echo "[$timestamp]TAS shutdown unexpectedly, restarting TAS now..." >> $TAS_LOG
echo $?
recover_tas
else
sleep 10
fi
done
It seems you have a daemon watching a daemon watching a daemon.
My normal method of testing the notification and escalation chain is to simulate a failure by causing one, for example blocking a port.
But this is thoroughly unsatisfying. I don't want down time recorded in nagios where there was none. I also don't want to wait.
Does anyone know a way to test a notification chain without causing the outage? For example something like this:
$ ./check_notifications_chain <service|host> <time down>
at <x> minutes notification email sent to group <people>
at <2x> minutes notification email sent to group <people>
at <3x> minutes escalated to group <management>
at <200x> rm -rf; shutdown -h now executed.
Extending this paradigm I might make the notification chain a nagios check in itself, but I'll stop here before my brain explodes.
Anyone?
If you only want to verify that the email alerts are working properly, you could create a simple test service, which generates a warning once a day.
test_alert.sh:
#!/bin/bash
date=`date -u +%H%M`
echo $date
echo "Nagios test script. Intentionally generates a warning daily."
if [[ "$date" -ge "1900" && "$date" -le "1920" ]] ; then
exit 1
else
exit 0
fi
commands.cfg:
define command{
command_name test_alert
command_line /bin/bash /usr/local/scripts/test_alert.sh
}
services.cfg:
define service {
host localhost
service_description Test Alert
check_command test_alert
use generic-service
}
This is an old post but maybe my solution can help someone.
I use the plugin "check_dummy" which is in the Nagios plugins pack.
As it says, it is stupid.
See some exemple of how it works :
Usage:
check_dummy <integer state> [optional text]
$ ./check_dummy 0
OK
$ ./check_dummy 2
CRITICAL
$ ./check_dummy 3 salut
UNKNOWN: salut
$ ./check_dummy 1 azerty
WARNING: azerty
$ echo $?
1
I create a file which contain the interger state and the optional text :
echo 0 OKAY | sudo tee /usr/local/nagios/libexec/dummy.txt
sudo chown nagios:nagios /usr/local/nagios/libexec/dummy.txt
With the command :
# Dummy check (notifications tests)
define command {
command_name my_check_dummy
command_line $USER1$/check_dummy $(cat /usr/local/nagios/libexec/dummy.txt)
}
Associated with the service description :
define service {
use generic-service
host_name localhost
service_description Dummy check
check_period 24x7
check_interval 1
max_check_attempts 1
retry_interval 1
notifications_enabled 1
notification_options w,u,c,r
notification_interval 0
notification_period 24x7
check_command my_check_dummy
}
So I just change the contents of the file "dummy.txt" to change the service state :
echo "2 Oups" | sudo tee /usr/local/nagios/libexec/dummy.txt
echo "1 AHHHH" | sudo tee /usr/local/nagios/libexec/dummy.txt
echo "0 Parfait !" | sudo tee /usr/local/nagios/libexec/dummy.txt
This allowed me to debug my notification program.
Hope it helps !