I got stuck in this problem. I need to run two commands in shell script, but they can't stop each other.
For example, this shell script:
psql database user &
gedit file
If I run these commands up, only the gedit process stays open and I can't see where the process of psql is.
But if I do this:
gedit file &
psql database user
I can see the psql's process, but it's closed by messages of gedit's process.
How can I execute this script without one process close the other?
If you want to suppress output from gedit:
gedit file >/dev/null 2>&1 &
psql database user
However, the claim:
I can see the psql's process, but it's closed by messages of gedit's process.
...simply doesn't happen: Messages from gedit go directly to the terminal; psql can't see them, so it can't possibly be exiting because of them.
Related
I have a VM that I want running indefinitely. The server is always running but I want the script to keep running after I log out. How would I go about doing so? Creating a cron job?
In general the following steps are sufficient to convince most Unix shells that the process you're launching should not depend on the continued existence of the shell:
run the command under nohup
run the command in the background
redirect all file descriptors that normally point to the terminal to other locations
So, if you want to run command-name, you should do it like so:
nohup command-name >/dev/null 2>/dev/null </dev/null &
This tells the process that will execute command-name to send all stdout and stderr to nowhere (instead of to your terminal) and also to read stdin from nowhere (instead of from your terminal). Of course if you actually have locations to write to/read from, you can certainly use those instead -- anything except the terminal is fine:
nohup command-name >outputFile 2>errorFile <inputFile &
See also the answer in Petur's comment, which discusses this issue a fair bit.
I have written a batch file like this:
Start putty.exe -ssh 172.17.0.52 -l root -m dummy.txt
Then in dummy.text I have written this command:
avahi-daemon --no-drop-root -D
export XVHMI_USERCONFIG_PATH=/home/UserProfileConfig
export XDG_RUNTIME_DIR=/tmp
cd /opt/bosch/airis/bin
When I run the .bat file, PuTTY starts, commands execute (hopefully, not sure) and it exits.
How to keep that window open?
I have googled for the same, but no solid help. I read on stack overflow itself that we need to define something in txt file, but what and most importantly how?
The SSH session closes (and PuTTY with it) as soon as the command finishes. Normally the "command" is shell. As you have overridden this default "command" and yet you want to run the shell nevertheless, you have to explicitly execute the shell yourself:
avahi-daemon ... ; /bin/bash
Also as use of -m switch implies a non-interactive terminal, you probably want to force an interactive terminal back using -t switch.
Though, I'm not really sure if you want to execute shell or if you just want to see your command output. If the latter, did you consider using plink? It's console terminal client from PuTTY package. Being console application, it inherits console of parent batch file, and you can pause the batch console from closing using pause command, if needed.
Another option (both for PuTTY and plink) is to pause on remote side. E.g. Using read command.
avahi-daemon ... ; read
As suggested by Martin I tried this step:
putty.exe -ssh 172.17.0.52 -l root -m dummy.txt -t
added /bin/bash at the end of commands in dummy.txt
It worked for me. Please note, you have to follow both the steps as mentioned above.
This way you can keep the session alive and can manually execute further commands.
So, I have a long running script (of order few days) say execute.sh which I am planning to execute on a server on which I have a user account...
Now, I want to execute this script so that it runs forever even if I logoff or disconnect from the server??
How do i do that?
THanks
You have a couple of choices. The most basic would be to use nohup:
nohup ./execute.sh
nohup executes the command as a child process and detaches from terminal and continues running if it receives SIGHUP. This signal means sig hangup and will getting triggered if you close a terminal and a process is still attached to it.
The output of the process will getting redirected to a file, per default nohup.out located in the current directory.
You may also use bash's disown functionality. You can start a script in bash:
./execute.sh
Then press Ctrl+z and then enter:
disown
The process will now run in background, detached from the terminal. If you care about the scripts output you may redirect output to a logfile:
./execute.sh > execute.log 2>&1
Another option would be to install screen on the remote machine, run the command in a screen session and detach from it. You'll find a lot of tutorials about this.
nohup (no hangup) it and run it in the background:
nohup execute.sh &
Output that normally would have gone to the screen (STDOUT) will go to a file called nohup.out.
I am using elastic map reduce from Amazon. I am sshing into hadoop master node and executing a script like.
$EMR_BIN/elastic-mapreduce --jobflow $JOBFLOW --ssh < hivescript.sh . It sshes me into the master node and runs the hive script. The hivescript contains the following lines
hive
add jar joda-time-1.6.jar;
add jar EmrHiveUtils-1.2.jar;
and some commands to create hive tables. The script runs fine and creates the hive tables and everything else, but comes back to the prompt from where I ran the script. How do I leave it sshed into hadoop master node at the hive prompt.
Consider using Expect, then you could do something along these lines and interact at the end:
/usr/bin/expect <<EOF
spawn ssh ... YourHost
expect "password"
send "password\n"
send javastuff
interact
EOF
These are the most common answers I've seen (with the drawbacks I ran into with them):
Use expect
This is probably the most well rounded solution for most people
I cannot control whether expect is installed in my target environments
Just to try this out anyway, I put together a simple expect script to ssh to a remote machine, send a simple command, and turn control over to the user. There was a long delay before the prompt showed up, and after fiddling with it with little success I decided to move on for the time being.
Eventually I came back to this as the final solution after realizing I had violated one of the 3 virtues of a good programmer -- false impatience.
Use screen / tmux to start the shell, then inject commands from an external process.
This works ok, but if the terminal window dies it leaves a screen/tmux instance hanging around. I could certainly try to come up with a way to just re-attach to prior instances or kill them; screen (and probably tmux) can make it die instead of auto-detaching, but I didn't fiddle with it.
If using gnome-terminal, use its -x or --command flag (I'm guessing xterm and others have similar options)
I'll go into more detail on problems I had with this on #4
Make a bash script with #!/bin/bash --init-file as the shebang; this will cause your script to execute, then leave an interactive shell running afterward
This and #3 had issues with some programs that required user interaction before the shell is presented to them. Some programs (like ssh) it worked fine with, others (telnet, vxsim) presented a prompt but no text was passed along to the program; only ctrl characters like ^C.
Do something like this: xterm -e 'commands; here; exec bash'. This will cause it to create an interactive shell after your commands execute.
This is fine as long as the user doesn't attempt to interrupt with ^C before the last command executes.
Currently, the only thing I've found that gives me the behavior I need is to use cmdtool from the OpenWin project.
/usr/openwin/bin/cmdtool -I 'commands; here'
# or
/usr/openwin/bin/cmdtool -I 'commands; here' /bin/bash --norc
The resulting terminal injects the list of commands passed with -I to the program executed (no parms means default shell), so those commands show up in that shell's history.
What I don't like is that the terminal cmdtool provides feels so clunky ... but alas.
I logged in to a remote server via ssh and started a php script. Appereantly, it will take 17 hours to complete, is there a way to break the connection but the keep the script executing? I didn't make any output redirection, so I am seeing all the output.
Can you stop the process right now? If so, launch screen, start the process and detach screen using ctrl-a then ctrl-d. Use screen -r to retrieve the session later.
This should be available in most distros, failing that, a package will definitely be available for you.
ctrl + z
will pause it. Than type
bg
to send it to background. Write down the PID of the process for later usage ;)
EDIT: I forgot, you have to execute
disown -$PID
where $PID is the pid of your process
after that, and the process will not be killed after you close the terminal.
you described it's important to protect script continuation. Unfortunately I don't know, you make any interaction with script and script is made by you.
continuation protects 'screen' command. your connection will break, but screen protect pseudo terminal, you can reconnect to this later, see man.
if you don't need operators interaction with script, you simply can put script to background at the start, and log complete output into log file. Simply use command:
nohup /where/is/your.script.php >output.log 2&>1 &
>output.log will redirect output into log file, 2&>1 will append error stream into output, effectively into log file. last & will put command into background. Notice, nohup command will detach process from terminal group.
At now you can safely exit from ssh shell. Because your script is out of terminal group, then it won't be killed. It will be rejoined from your shell process, into system INIT process. It is unix like system behavior. Complete output you can monitor using command
tail -f output.log #allways breakable by ^C, it is only watching
Using this method you do not need use ^Z , bg etc shell tricks for putting command to the background.
Notice, using redirection to nohup command is preferred. Otherwise nohup will auto redirect all outputs for you to nohup.out file in the current directory.
You can use screen.