I have a minicom script which sends some commands via serial and expects something back(which works) but im having trouble exiting the minicom screen.
Below is the minicom script:
success1:
print \nSuccessfully received running!
send "exit"
exit 0
success2:
print \nSuccessfully received degrading!
! killall -9 minicom
exit
I was using ! killall -9 minicom which is recommended on their documentation but unfortunately, when running the script on Jenkins, it fails due to exit code 137 (Another process sent a signal 9). However this does exit minicom, just not successfully.
On the other hand, the 'send "exit"' just logs out of the device, and doesnt exit minicom.
How can i exit minicom and receive a 0 exit code?
you need to feed <stdin> with three characters: <ctrl-A>x<enter>
prepare the file escape.txt using vi in order to write ^Ax^M
launch minicom script
/bin/rm -f capture.txt; ( minicom -D /dev/ttyUSB0 -S test_minicom.macro -C capture.txt < escape.txt ) ; cat capture.txt
To build on what Diego shared, if you just need to exit minicom without error and don't care about capturing the exit code, build escape.txt as Diego described then you only need to run:
( minicom -D /dev/ttyUSB0 -S test_minicom.macro -C capture.txt < escape.txt )
This proves to be very helpful for automatic provisioning like with Ansible!
As an alternative to creating the escape.txt file, you can use echo to send the exit sequence.
Building on the above answers:
$ /bin/rm -f capture.txt; ( echo -ne "\x01x\r" ) | minicom -D /dev/ttyUSB0 -S test_minicom.macro -C capture.txt; cat capture.txt
To break down the echo command a little,
-n removes the default line-feed \n
-e tells echo to interpret escape sequences
\x01 is the escape sequence for ^A (start-of-heading)
x tells minicom to exit
\r sends a ^M carriage-return
Hex output from echo:
$ echo -ne "\x01x\r" | od -A x -t x1a -v
000000 01 78 0d
soh x cr
000003
Note: If you just want to send some text and don't need the full minicom scripting you can add an extra echo. Sleep may not be needed depending on command run and if you care about output in capture.txt...
$ /bin/rm -f capture.txt; ( echo "poweroff"; sleep 1; echo -ne "\x01x\r" ) | minicom -D /dev/ttyUSB0 -C capture.txt; cat capture.txt
I need to know an another process pid which is executed as a command in the bash script like a nmap scan etc as an when the process is created I can display a bar or a spinner
#!/bin/sh
G='\033[0;32m'
B='\033[0m'
${G}Enter IP TAIL LIKE 0.1 OR 1.1${B}"
read v
${G}ENTER Device NAME ${B}"
read k
nmap -A -Pn -sV 192.168.$v -oN /tmp/op
//here i want a while loop for displaying a spinner
edit code is updated Thts the code in case tht was not visible properly ^^
As the pid dies when its completed I can use it as a count or a flag or something similar to end the spinner.
I'm working on Kali nethunter.
P.S This is my first time on stack overflow pls forgive me if its too stupid or tell me if I missed something.
A starting point:
#!/bin/bash
echo "Enter IP:"
read -r ip
# `&` runs in parallel
# always quote variables
nmap "$ip" &
# `$!` get's the background process PID
pid=$!
...
# you can see if a pid is running by checking exit status of `kill -0`
while kill -0 "$pid" 2>&1 >/dev/null; do
printf ...
...
done
nmap -A -Pn -sV 192.168.0.1 -p -oN /tmp/op >/dev/null & pid=$!
i=1
sp="/-\|"
echo -n ' '
while kill -0 "$pid" 2>&1 >/dev/null;
do
printf "\b${sp:i++%${#sp}:1}"
done
*Problem solved thanks to * kamil cuk
The following script works as expected when executed from an Applescript do shell script command.
#!/bin/sh
sleep 10 &
#echo "hello world" > /tmp/apipe &
cpid=$!
sleep 1
if ps -ef | grep $cpid | grep sleep | grep -qv grep ; then
echo "killing blocking cmd..."
kill -KILL $cpid
# non zero status to inform launch script of problem...
exit 1
fi
But, if the sleep command (line 2) is swaped to the echo command in (line 3) together with the if statement, the script blocks when run from Applescript but runs fine from the terminal command line.
Any ideas?
EDIT: I should have mentioned that the script works properly when a consumer/reader is connected to the pipe. It only block when nothing is reading from the pipe...
OK, the following will do the trick. It basically kills the job using its jobid. Since there is only one, it's the current job %%.
I was lucky that I came across the this answer or it would have driven me crazy :)
#!/bin/sh
echo $1 > $2 &
sleep 1
# Following is necessary. Seems to need it or
# job will not complete! Also seen at
# https://stackoverflow.com/a/10736613/348694
echo "Checking for running jobs..."
jobs
kill %% >/dev/null 2>&1
if [ $? -eq 0 ] ; then
echo "Taking too long. Killed..."
exit 1
fi
exit 0
I'm wondering if there is a better way to make a daemon that waits for something using only sh than:
#! /bin/sh
trap processUserSig SIGUSR1
processUserSig() {
echo "doing stuff"
}
while true; do
sleep 1000
done
In particular, I'm wondering if there's any way to get rid of the loop and still have the thing listen for the signals.
Just backgrounding your script (./myscript &) will not daemonize it. See http://www.faqs.org/faqs/unix-faq/programmer/faq/, section 1.7, which describes what's necessary to become a daemon. You must disconnect it from the terminal so that SIGHUP does not kill it. You can take a shortcut to make a script appear to act like a daemon;
nohup ./myscript 0<&- &>/dev/null &
will do the job. Or, to capture both stderr and stdout to a file:
nohup ./myscript 0<&- &> my.admin.log.file &
Redirection explained (see bash redirection)
0<&- closes stdin
&> file sends stdout and stderr to a file
However, there may be further important aspects that you need to consider. For example:
You will still have a file descriptor open to the script, which means that the directory it's mounted in would be unmountable. To be a true daemon you should chdir("/") (or cd / inside your script), and fork so that the parent exits, and thus the original descriptor is closed.
Perhaps run umask 0. You may not want to depend on the umask of the caller of the daemon.
For an example of a script that takes all of these aspects into account, see Mike S' answer.
Some of the top-upvoted answers here are missing some important parts of what makes a daemon a daemon, as opposed to just a background process, or a background process detached from a shell.
This http://www.faqs.org/faqs/unix-faq/programmer/faq/ describes what is necessary to be a daemon. And this Run bash script as daemon implements the setsid, though it misses the chdir to root.
The original poster's question was actually more specific than "How do I create a daemon process using bash?", but since the subject and answers discuss daemonizing shell scripts generally, I think it's important to point it out (for interlopers like me looking into the fine details of creating a daemon).
Here's my rendition of a shell script that would behave according to the FAQ. Set DEBUG to true to see pretty output (but it also exits immediately rather than looping endlessly):
#!/bin/bash
DEBUG=false
# This part is for fun, if you consider shell scripts fun- and I do.
trap process_USR1 SIGUSR1
process_USR1() {
echo 'Got signal USR1'
echo 'Did you notice that the signal was acted upon only after the sleep was done'
echo 'in the while loop? Interesting, yes? Yes.'
exit 0
}
# End of fun. Now on to the business end of things.
print_debug() {
whatiam="$1"; tty="$2"
[[ "$tty" != "not a tty" ]] && {
echo "" >$tty
echo "$whatiam, PID $$" >$tty
ps -o pid,sess,pgid -p $$ >$tty
tty >$tty
}
}
me_DIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" && pwd )"
me_FILE=$(basename $0)
cd /
#### CHILD HERE --------------------------------------------------------------------->
if [ "$1" = "child" ] ; then # 2. We are the child. We need to fork again.
shift; tty="$1"; shift
$DEBUG && print_debug "*** CHILD, NEW SESSION, NEW PGID" "$tty"
umask 0
$me_DIR/$me_FILE XXrefork_daemonXX "$tty" "$#" </dev/null >/dev/null 2>/dev/null &
$DEBUG && [[ "$tty" != "not a tty" ]] && echo "CHILD OUT" >$tty
exit 0
fi
##### ENTRY POINT HERE -------------------------------------------------------------->
if [ "$1" != "XXrefork_daemonXX" ] ; then # 1. This is where the original call starts.
tty=$(tty)
$DEBUG && print_debug "*** PARENT" "$tty"
setsid $me_DIR/$me_FILE child "$tty" "$#" &
$DEBUG && [[ "$tty" != "not a tty" ]] && echo "PARENT OUT" >$tty
exit 0
fi
##### RUNS AFTER CHILD FORKS (actually, on Linux, clone()s. See strace -------------->
# 3. We have been reforked. Go to work.
exec >/tmp/outfile
exec 2>/tmp/errfile
exec 0</dev/null
shift; tty="$1"; shift
$DEBUG && print_debug "*** DAEMON" "$tty"
# The real stuff goes here. To exit, see fun (above)
$DEBUG && [[ "$tty" != "not a tty" ]] && echo NOT A REAL DAEMON. NOT RUNNING WHILE LOOP. >$tty
$DEBUG || {
while true; do
echo "Change this loop, so this silly no-op goes away." >/dev/null
echo "Do something useful with your life, young padawan." >/dev/null
sleep 10
done
}
$DEBUG && [[ "$tty" != "not a tty" ]] && sleep 3 && echo "DAEMON OUT" >$tty
exit # This may never run. Why is it here then? It's pretty.
# Kind of like, "The End" at the end of a movie that you
# already know is over. It's always nice.
Output looks like this when DEBUG is set to true. Notice how the session and process group ID (SESS, PGID) numbers change:
<shell_prompt>$ bash blahd
*** PARENT, PID 5180
PID SESS PGID
5180 1708 5180
/dev/pts/6
PARENT OUT
<shell_prompt>$
*** CHILD, NEW SESSION, NEW PGID, PID 5188
PID SESS PGID
5188 5188 5188
not a tty
CHILD OUT
*** DAEMON, PID 5198
PID SESS PGID
5198 5188 5188
not a tty
NOT A REAL DAEMON. NOT RUNNING WHILE LOOP.
DAEMON OUT
# double background your script to have it detach from the tty
# cf. http://www.linux-mag.com/id/5981
(./program.sh &) &
Use your system's daemon facility, such as start-stop-daemon.
Otherwise, yes, there has to be a loop somewhere.
$ ( cd /; umask 0; setsid your_script.sh </dev/null &>/dev/null & ) &
It really depends on what is the binary itself going to do.
For example I want to create some listener.
The starting Daemon is simple task :
lis_deamon :
#!/bin/bash
# We will start the listener as Deamon process
#
LISTENER_BIN=/tmp/deamon_test/listener
test -x $LISTENER_BIN || exit 5
PIDFILE=/tmp/deamon_test/listener.pid
case "$1" in
start)
echo -n "Starting Listener Deamon .... "
startproc -f -p $PIDFILE $LISTENER_BIN
echo "running"
;;
*)
echo "Usage: $0 start"
exit 1
;;
esac
this is how we start the daemon (common way for all /etc/init.d/ staff)
now as for the listener it self,
It must be some kind of loop/alert or else that will trigger the script
to do what u want. For example if u want your script to sleep 10 min
and wake up and ask you how you are doing u will do this with the
while true ; do sleep 600 ; echo "How are u ? " ; done
Here is the simple listener that u can do that will listen for your
commands from remote machine and execute them on local :
listener :
#!/bin/bash
# Starting listener on some port
# we will run it as deamon and we will send commands to it.
#
IP=$(hostname --ip-address)
PORT=1024
FILE=/tmp/backpipe
count=0
while [ -a $FILE ] ; do #If file exis I assume that it used by other program
FILE=$FILE.$count
count=$(($count + 1))
done
# Now we know that such file do not exist,
# U can write down in deamon it self the remove for those files
# or in different part of program
mknod $FILE p
while true ; do
netcat -l -s $IP -p $PORT < $FILE |/bin/bash > $FILE
done
rm $FILE
So to start UP it : /tmp/deamon_test/listener start
and to send commands from shell (or wrap it to script) :
test_host#netcat 10.184.200.22 1024
uptime
20:01pm up 21 days 5:10, 44 users, load average: 0.62, 0.61, 0.60
date
Tue Jan 28 20:02:00 IST 2014
punt! (Cntrl+C)
Hope this will help.
Have a look at the daemon tool from the libslack package:
http://ingvar.blog.linpro.no/2009/05/18/todays-sysadmin-tip-using-libslack-daemon-to-daemonize-a-script/
On Mac OS X use a launchd script for shell daemon.
If I had a script.sh and i wanted to execute it from bash and leave it running even when I want to close my bash session then I would combine nohup and & at the end.
example: nohup ./script.sh < inputFile.txt > ./logFile 2>&1 &
inputFile.txt can be any file. If your file has no input then we usually use /dev/null. So the command would be:
nohup ./script.sh < /dev/null > ./logFile 2>&1 &
After that close your bash session,open another terminal and execute: ps -aux | egrep "script.sh" and you will see that your script is still running at the background. Of cource,if you want to stop it then execute the same command (ps) and kill -9 <PID-OF-YOUR-SCRIPT>
See Bash Service Manager project: https://github.com/reduardo7/bash-service-manager
Implementation example
#!/usr/bin/env bash
export PID_FILE_PATH="/tmp/my-service.pid"
export LOG_FILE_PATH="/tmp/my-service.log"
export LOG_ERROR_FILE_PATH="/tmp/my-service.error.log"
. ./services.sh
run-script() {
local action="$1" # Action
while true; do
echo "### Running action '${action}'"
echo foo
echo bar >&2
[ "$action" = "run" ] && return 0
sleep 5
[ "$action" = "debug" ] && exit 25
done
}
before-start() {
local action="$1" # Action
echo "* Starting with $action"
}
after-finish() {
local action="$1" # Action
local serviceExitCode=$2 # Service exit code
echo "* Finish with $action. Exit code: $serviceExitCode"
}
action="$1"
serviceName="Example Service"
serviceMenu "$action" "$serviceName" run-script "$workDir" before-start after-finish
Usage example
$ ./example-service
# Actions: [start|stop|restart|status|run|debug|tail(-[log|error])]
$ ./example-service start
# Starting Example Service service...
$ ./example-service status
# Serive Example Service is runnig with PID 5599
$ ./example-service stop
# Stopping Example Service...
$ ./example-service status
# Service Example Service is not running
Here is the minimal change to the original proposal to create a valid daemon in Bourne shell (or Bash):
#!/bin/sh
if [ "$1" != "__forked__" ]; then
setsid "$0" __forked__ "$#" &
exit
else
shift
fi
trap 'siguser1=true' SIGUSR1
trap 'echo "Clean up and exit"; kill $sleep_pid; exit' SIGTERM
exec > outfile
exec 2> errfile
exec 0< /dev/null
while true; do
(sleep 30000000 &>/dev/null) &
sleep_pid=$!
wait
kill $sleep_pid &>/dev/null
if [ -n "$siguser1" ]; then
siguser1=''
echo "Wait was interrupted by SIGUSR1, do things here."
fi
done
Explanation:
Line 2-7: A daemon must be forked so it doesn't have a parent. Using an artificial argument to prevent endless forking. "setsid" detaches from starting process and terminal.
Line 9: Our desired signal needs to be differentiated from other signals.
Line 10: Cleanup is required to get rid of dangling "sleep" processes.
Line 11-13: Redirect stdout, stderr and stdin of the script.
Line 16: sleep in the background
Line 18: wait waits for end of sleep, but gets interrupted by (some) signals.
Line 19: Kill sleep process, because that is still running when signal is caught.
Line 22: Do the work if SIGUSR1 has been caught.
Guess it does not get any simpler than that.
Like many answers this one is not a "real" daemonization but rather an alternative to nohup approach.
echo "script.sh" | at now
There are obviously differences from using nohup. For one there is no detaching from the parent in the first place. Also "script.sh" doesn't inherit parent's environment.
By no means this is a better alternative. It is simply a different (and somewhat lazy) way of launching processes in background.
P.S. I personally upvoted carlo's answer as it seems to be the most elegant and works both from terminal and inside scripts
try executing using &
if you save this file as program.sh
you can use
$. program.sh &
My connection is flaky, however I have a backup one. I made some bash script to check for connectivity and change connection if the present one is dead. Please help me improve them.
The scripts almost works, except for not waiting long enough to receive an IP (it cycles to next step in the until loop too quick). Here goes:
#!/bin/bash
# Invoke this script with paths to your connection specific scripts, for example
# ./gotnet.sh ./connection.sh ./connection2.sh
until [ -z "$1" ] # Try different connections until we are online...
do
if eval "ping -c 1 google.com"
then
echo "we are online!" && break
else
$1 # Runs (next) connection-script.
echo
fi
shift
done
echo # Extra line feed.
exit 0
And here is an example of the slave scripts:
#!/bin/bash
ifconfig wlan0 down
ifconfig wlan0 up
iwconfig wlan0 key 1234567890
iwconfig wlan0 essid example
sleep 1
dhclient -1 -nw wlan0
sleep 3
exit 0
Here's one way to do it:
#!/bin/bash
while true; do
if ! [ "`ping -c 1 google.com; echo $?`" ]; then #if ping exits nonzero...
./connection_script1.sh #run the first script
sleep 10 #give it a few seconds to complete
fi
if ! [ "`ping -c 1 google.com; echo $?`" ]; then #if ping *still* exits nonzero...
./connection_script2.sh #run the second script
sleep 10 #give it a few seconds to complete
fi
sleep 300 #check again in five minutes
done
Adjust the sleep times and ping count to your preference. This script never exits so you would most likely want to run it with the following command:
./connection_daemon.sh 2>&1 > /dev/null & disown
Have you tried omitting the -nw option from the dhclient command?
Also, remove the eval and quotes from your if they aren't necessary. Do it like this:
if ping -c 1 google.com > /dev/null 2>&1
Trying using ConnectTimeout ${timeout} somewhere.