[SOLVED] bash how to wait in script from the previous command to finish

pedropt · 03-17-2017, 07:17 PM

Hi everyone

Ayone here have an idea how to hang a bash script until previous command is finished ?

I an opening a gnome-terminal from a bash script and i need the current script to wait until gnome-terminal finishes its job

example :

Quote:

gnome-terminal -e "msfconsole -r test.rc > out.tmp"
cat out.tmp

what happens here is that cat command is not waiting for gnome terminal to finish its job , and then says that out.tmp does not exist .

Is there a way to make cat command wait until gnome terminal finishes ?

nodir · 03-17-2017, 09:14 PM

probably the && operator will do that, give it a try.
man bash

Code:

       AND  and  OR lists are sequences of one or more pipelines separated by the && and || control operators, respectively.  AND and OR lists
       are executed with left associativity.  An AND list has the form

              command1 && command2

       command2 is executed if, and only if, command1 returns an exit status of zero.

there is also "wait", but i got no experience with it.
user$ type wait
wait is a shell builtin

frankbell · 03-17-2017, 09:39 PM

"&&" definitely.

From the bash man page.

Quote:

command1 && command2
command2 is executed if, and only if, command1 returns an exit status of zero.

pedropt · 03-17-2017, 10:01 PM

Thanks for the reply , but i already try that without success .

Quote:

gnome-terminal -e "msfconsole -r test.rc > out.tmp" && cat out.tmp

Turbocapitalist · 03-17-2017, 10:19 PM

Do you want the text to be displayed inside the actual gnome-terminal that you have launched? If so, move everything to inside the quotes:

Code:

gnome-terminal -e "msfconsole -r test.rc > out.tmp && cat out.tmp"

agillator · 03-17-2017, 10:21 PM

I think you actually have two commands on the line. The first is 'gnome-terminal -e "msfconsole -r test.rc > out.tmp"' and the second is 'cat out.tmp'. If the first runs successfully then the second will run. Gnome-terminal runs successfully regardless of the outcome of msfconsle . . . . Therefore the cat instruction always tries to run.

I would suggest you break the actions down. I'm guessing you are running this in a terminal to begin with. If so, run the msfconsole command first. Then set a variable to the result ($?). Then use an if statement to decide whether to run the cat command based on the value of of the result variable. It is a slightly more complicated approach, but it should do what I think you want. Of course these commands could be put in a script and then run it by the gnome-terminal command.

agillator · 03-17-2017, 10:22 PM

Turbocapitalist answered while I was typing mine. His answer is simpler although both really do the same thing.

ondoho · 03-18-2017, 03:00 AM

different approach:
gnome-terminal is probably already running as a daemon in the background, that's why it doesn't work.
Use a different terminal, like xterm.

pan64 · 03-18-2017, 04:26 AM

I don't know what is msfconsole, so just ask: why do you need terminal at all?

Code:

msfconsole -r test.rc > out.tmp && cat out.tmp 
# should work too, or probably:
msfconsole -r test.rc | tee out.tmp
# is enough

pedropt · 03-18-2017, 07:25 AM

If i use xterm i can do it , but somehow with xterm i am having some issues in msfconsole and this is the reason why i want to test with gnome terminal .

Quote:

msfconsole -r test.rc > out.tmp && cat out.tmp

does not work because this command will launch gnome-terminal , and after release gnome-terminal it will execute the next command no matter if gnome-terminal is still running or not .

I need some code that open gnome terminal , waits for it to close and then run the second command .
Only this way is possible .

One idea was getting pid of gnome terminal and wait for it do close and then run the 2nd command .

i need the main script to wait until those commands are finished , and the problem is that the main script is not waiting .

Habitual · 03-18-2017, 07:55 AM

Code:

gnome-terminal -e "msfconsole -r test.rc > out.tmp" ; sleep 30s ; cat out.tmp

adjust sleep to suit.

May have the closing quote in the wrong place...
Might not be an "accident" either.

Question is
How to process Success or Failure of
msfconsole -r test.rc > out.tmp

Can get weird.
but I'd use /tmp/out.tmp and test it on the way "in"

[[ -f /tmp/out.tmp ]]
write it
do_work
rm it on the way out.

Code:

gnome-terminal -e "cat $(msfconsole -r test.rc > out.tmp)"

may work

Just sayin'

ntubski · 03-18-2017, 08:06 AM

Quote:

Originally Posted by pedropt

i need the main script to wait until those commands are finished , and the problem is that the main script is not waiting .

No, the main script is waiting, the problem is that the "gnome-terminal" command is some kind of funny wrapper which doesn't wait for the gnome terminal to close before exiting.

http://stackoverflow.com/a/8415989/319698

Quote:

there is no way to get gnome-terminal to behave differently.

pedropt · 03-18-2017, 10:23 AM

Quote:

gnome-terminal -e "msfconsole -r test.rc > out.tmp" ; sleep 30s ; cat out.tmp

or

Quote:

gnome-terminal -e "msfconsole -r test.rc > out.tmp"
sleep 30s
cat out.tmp

will not work if gnome-terminal takes more than 30 seconds to execute the command .

And alternative idea is :

Launch gnome terminal with the command .

then the next lines in script would be wait on a loop for out.tmp file to be created .
when out.tmp gets created then loop will stop and script will continue .

Anyone have an idea how to make something like this ?

The loop could be created i a function with if cause :

main script

Quote:

function outf(){
out=out.tmp
if [ -f $out ]; then
echo "Continuing the script"
else
echo "waiting for output from msfconsole"
sleep 2
outf
fi
}
bla
bla
bla
gnome-terminal -e "msfconsole -r test.rc > out.tmp"
outf
cat out.tmp

The only problem here would be if by some reason the msfconsole get an error and do not create the file .
In that case the outf function will be waiting forever .

pedropt · 03-18-2017, 10:44 AM

i think i got it

Quote:

function outf(){
out=out.tmp
sleep=$((sleep+1))
if [ $sleep == "10" ] then
echo "timeout - was not possible to get msfconsole output"
exit 1
fi

if [ -f $out ]; then
echo "Continuing the script"
else
echo "waiting for output from msfconsole"
sleep 2
outf
fi
}
bla
bla
bla
gnome-terminal -e "msfconsole -r test.rc > out.tmp"
sleep="1"
outf
cat out.tmp

There could be some errors in sentences because i made the code now just by hand and logic .

The logic is :
To wait for the result , i created a function to check for the file
but before that function is launched , i created a variable with a number .
Every time the function loops because file does not exist , it increases that variable one number ahead .
This means , that starts with 1 , and in every loop it add +1 = 2
when it gets to 10 then exits the script .
It means that when "sleep" gets to 10 it will be 20 seconds because i let a sleep 2s on the "file not found" if cause .
In mean time if file is created before that time then it continues the main script .

Note: the most hard thing in bash code is creating a code with logic .

pan64 · 03-18-2017, 11:55 AM

so why do you need terminal at all?