Ubuntu – How to kill a script running in terminal, without closing terminal (Ctrl + C doesn’t work)

bashscripts

I have written a bash script that calls several other programs and executes a bunch of commands. I run this script from the terminal. Now I want to kill the script.

Pressing Ctrl + C sometimes doesn't cut it, I think because sometimes the script is executing another program, and for some reason the kill signal doesn't work.

However, if I close the terminal window, it kills the script.

Is there something I can do (a keyboard combination), that is analogous to closing the terminal window, without actually closing the terminal window (I don't want to lose command history, current directory, output history, etc.)?

Best Answer

You have few options. One is to stop the script (CtrlZ), get the PID of the script and send SIGKILL to the process group.

When a command is executed in a shell, the process it starts and all its children are part of the same process group (in this case, the foreground process group). To send a signal to all processes in this group, you send it to the process leader. For the kill command, process leader is denoted thus:

kill -PID

Where PID is the process ID of the script.

Example:

Consider a script test.sh which launches some processes. Say you ran it in a shell:

$ ./test.sh

In another terminal,

$ pgrep test.sh
17802
$ pstree -ps `!!`
pstree -ps `pgrep test.sh`
init(1)───sshd(1211)───sshd(17312)───sshd(17372)───zsh(17788)───test.sh(17802)─┬─dd(17804)
                                                                               ├─sleep(17805)
                                                                               └─yes(17803)

In this case, to send a signal to process group created by test.sh, you'd do:

kill -INT -17802

-INT is used to send SIGINT, and so this command is the equivalent of pressing CtrlC on the terminal. To send SIGKILL:

kill -KILL -17802

You only need to stop the script if you can't open another terminal. If you can, use pgrep to find the PID.

One of the commands that the script launches may be trapping SIGINT, which is probably why CtrlC is ineffective. However, SIGKILL can't be trapped, and it is usually a last-resort option. You might want to try SIGTERM (-TERM) before going for the kill. Neither SIGKILL or SIGTERM can be set up as a keyboard shortcut the way SIGINT is.

All this is moot if your script doesn't contain a shebang line. From this SO answer:

Usually the parent shell guesses that the script is written for the the same shell (minimal Bourne-like shells run the script with /bin/sh, bash runs it as a bash subprocess) ...

Because of this, when the script is executed, you won't find a process named after script (or a process with the script's name in the command line) and pgrep will fail.

Always use a shebang line.

Related Solutions

Ubuntu – How to run a bash script without affecting the file system

Try using an overlay, with a chroot. First, decide the path you want to chroot to, and make sure it exists, and similarly for the path you will overlay on / (which is where modifications will go):

mkdir -p /chroot
mkdir -p /tmp/tmproot

I chose a directory in /tmp/ as it's a tmpfs on my system (possibly unadvisable, but OK for me), so no changes should reach the disk. You can use a squashfs and mount it somewhere, and use that as the overlay, but that has the problem of being read-only, I think.

Now:

$ mount -t overlayfs -o lowerdir=/,upperdir=/tmp/tmproot overlayfs /chroot/
$ chroot /chroot/ /bin/bash -l
root:/$ touch test
root:/$ ls
...  sys  test  tmp  ...
root:/$ logout
$ ls /
...  sys  tmp  ...
$ ls /tmp/tmproot/
root  test

If you make the upperdir independent of a physical disk (perhaps by using tmpfs), this should protect the lowerdir.

Note the creation of a root folder - that's for my .bash_history. A copy was made of the original .bash_history, and then appended to.

Ubuntu – Spawn new Terminator tabs from Bash script

First, open a terminator instance, split it into 4 panes as desired and save as a new layout (make sure to close all open terminal windows except the one you've set up with your new profile). For each of the 4 panes, add a custom command but just add the text COMMAND1, COMMAND2 etc. Save the new layout as foo (or whatever). At this point, your ~/.config/terminator/config should look something like this:

[global_config]
  enabled_plugins = LaunchpadCodeURLHandler, APTURLHandler, LaunchpadBugURLHandler
  focus = mouse
  suppress_multiple_term_dialog = True
  title_use_system_font = False
[keybindings]
[layouts]
  [[default]]
    [[[child0]]]
      fullscreen = False
      last_active_term = ad14f6cd-bcc3-4a80-9852-3fe64f7fc2eb
      last_active_window = True
      maximised = False
      order = 0
      parent = ""
      size = 735, 474
      title = sometitle
      type = Window
  [[foo]]
    [[[child0]]]
      fullscreen = False
      last_active_term = 18ebf009-c427-4c2f-8017-78c379a72d31
      last_active_window = True
      maximised = False
      order = 0
      parent = ""
      position = 2730:254
      size = 735, 474
      title = NAME-1
      type = Window
    [[[child1]]]
      order = 0
      parent = child0
      position = 237
      ratio = 0.5
      type = VPaned
    [[[child2]]]
      order = 0
      parent = child1
      position = 368
      ratio = 0.500680272109
      type = HPaned
    [[[child5]]]
      order = 1
      parent = child1
      position = 368
      ratio = 0.500680272109
      type = HPaned
    [[[terminal3]]]
      command = COMMAND1
      order = 0
      parent = child2
      profile = default
      title = NAME-1
      type = Terminal
      uuid = 01e46a5a-0a12-4861-a81e-e376af6041a7
    [[[terminal4]]]
      command = COMMAND2
      order = 1
      parent = child2
      profile = default
      type = Terminal
      uuid = 094d544d-944c-48a7-9960-00370253e799
    [[[terminal6]]]
      command = COMMAND3
      order = 0
      parent = child5
      profile = default
      type = Terminal
      uuid = fe19f601-1963-4af7-8870-f90e289d3d27
    [[[terminal7]]]
      command = COMMAND4
      order = 1
      parent = child5
      profile = default
      type = Terminal
      uuid = 18ebf009-c427-4c2f-8017-78c379a72d31
[plugins]
[profiles]
  [[default]]
    cursor_color = "#aaaaaa"
    font = Monaco 11
    scrollback_infinite = True
    scrollback_lines = 5000
    use_system_font = False

Now, modify your bash script to replace COMMANDN with the actual command you need to run:

#!/bin/bash

## change these to whatever you actually need
command1="echo one; bash"
command2="echo two; bash"
command3="tail -f /var/log/messages; bash"
command4="top"

## Modify terminator's config
sed -i.bak "s#COMMAND1#$command1#; s#COMMAND2#$command2#; s#COMMAND3#$command3#; s#COMMAND4#$command4#;" ~/.config/terminator/config

## Launch a terminator instance using the new layout
terminator -l foo

## Return the original config file
mv ~/.config/terminator/config.bak ~/.config/terminator/config

Running that script will now open a new terminal window with 4 panes, each running one of your commands.

Important: if the command is something that runs and then exits (as opposed to something like top which runs until you tell it to stop), you need COMMAN; bash as the command so that a new shell will be started. Otherwise, the command will run and the shell will exit immediately. That's why I have ; bash after each command except top in y script.

Best Answer

Related Solutions

Ubuntu – How to run a bash script without affecting the file system

Ubuntu – Spawn new Terminator tabs from Bash script

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