程式扎記: [Linux 文章收集] tmux Tutorial - Split Terminal Windows Easily

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2015年1月16日 星期五

[Linux 文章收集] tmux Tutorial - Split Terminal Windows Easily

Source From Here 
Terminal and Terminator 
It was long time ago when I realized that the major part of my work is being done in the Linux terminal. This is why I pay attention to things like shell and GNU tools, because knowing them well is often more than a half of job done. 

Afterwards, I found out that having just one terminal window is not enough. Even though having many windows (represented by tabs in Linux terminal-handling tools or by many Putty instances) can solve this problem, it is often desired to keep things in sight at the same time. For example, we may want to execute some code or tests and at the same time watch over log files by using tail. 

Terminator seemed to me the right tool to do the job. It's easy to install and it does exactly what it's supposed to do - it can split terminal windows both horizontally and vertically, according to user's requirements. It also allows to keep multiple tabs opened in case splitting one window is not enough. Its important disadvantage is that Terminator is a GUI tool, so it won't work if an X server is not at hand

Terminator in action: 
 

Of course, there is also the screen tool, but it has always been somehow mysterious to me. I was using it to run tasks in the background and to avoid problems caused by losing connection with remote machine. But I've never been brave enough to give screen the charge over my terminal windows and panes. I was pleased with Terminator, but then I found tmux

Tmux lies somewhere between Terminator and screen, combining ease of use with basing on the plain terminal only. The advantages of tmux over Terminator: 
* Portability - tmux works on all systems able to handle plain, old terminal.
* Scriptability - tmux can be scripted, so that setting up windows and panes takes nothing more than one or two keystrokes.
* Server-client architecture - tmux can be used to share sessions between users.
* Tweaks and options - both tmux and Terminator are easy to get with, but it's tmux that allows to go further and offers wide range of configuration hacks.

Beginning With tmux 
This is what a tmux session looks like: 
 

By reading this section, you'll get to know how to use tmux to split terminal window into panes and how to use multiple windows. This will let you do 90% of your work. The first thing you should know is that Ctrl+b is the default prefix in tmux. It means that running any command requires typing in the prefix first. As you probably have guessed, this is to avoid conflicts with key combinations used in other programs run in the terminal. 

Here is a list of a few basic tmux commands: 
Ctrl+b " - split pane horizontally.
Ctrl+b % - split pane vertically.
Ctrl+b arrow key - switch pane.
Hold Ctrl+b, don't release it and hold one of the arrow keys - resize pane.
Ctrl+b c - (c)reate a new window.
Ctrl+b n - move to the (n)ext window.
Ctrl+b p - move to the (p)revious window.
Ctrl+b x - kill pane (Or Ctrl+D)
Ctrl+b , Alt+Arrow key - Adjust pane size 

Other thing worth knowing is that scrolling is enabled by pressing Ctrl+b PgUp/PgDown. In fact, it enables the copy mode, which can also be done by pressingCtrl+b [. When in copy mode, you can use PgUp/PgDown and arrow keys to scroll through the terminal contents. To (q)uit the copy mode, simply press the q key.

Adjusting tmux 
Your tmux configuration file should be named .tmux.conf and stored in your home directory. This is a regular text file and it's the key to adjusting tmux. Just remember that after every modification, tmux must be refreshed to take new settings into account. This can be achieved either by restarting it or by typing in: 
$ tmux source-file .tmux.conf

Let's start modifying .tmux.conf with a simple example. 

Changing the Prefix 
As we said before, tmux uses the prefix to distinguish between commands sent to tmux itself and programs running inside of it. As the default prefix (Ctrl+b) is pretty awkward, we'll replace it with Ctrl+a, which is both easier to use (a is located closer to Ctrl than b) and time-honored, as the screen tool has been using it since a long time. To change the prefix, we need to open the .tmux.conf file and type in: 
  1. unbind C-b  
  2. set -g prefix C-a  
Pane switching with Alt+arrow 
For pane switching, Alt+arrow key combination (which is default in Terminator) worked fine for me and didn't cause any conflicts so far, so I think it will work fine in tmux, too. But it is of course a matter of taste and you can use whatever key you want. To switch panes with Alt, you can use these directives: 
  1. bind -n M-Left select-pane -L  
  2. bind -n M-Right select-pane -R  
  3. bind -n M-Up select-pane -U  
  4. bind -n M-Down select-pane -D  
Activity Monitoring 
If you have many tmux windows opened, you might want to get notified when something happens inside other windows. Pasting this: 
  1. setw -g monitor-activity on  
  2. set -g visual-activity on  
into the .tmux.conf file will cause tmux to write a message and highlight the window inside of which the activity took place (that is, something was written to the output). 

Highlighting Current Window Using Specified Colour 
Pasting the following: 
  1. set-window-option -g window-status-current-bg yellow  
into the configuration file enables highlighting the current window using the yellow colour. You may also specify one of: "black", "red", "green", "blue", "magenta", "cyan" and "white" or write "colour\d+", e.g. "colour5" or "colour170", which picks a color from the terminal's palette. 

Pane Switching Using Mouse 
In order to make migration from Terminator a little bit easier, you can modify tmux configuration file to allow pane switching using your mouse: 
  1. set-option -g mouse-select-pane on  
Of course, this may be considered as an undesirable behaviour, as the tmux allows to boost productivity by not requiring to touch the mouse at all. 

.bashrc Problem 
I don't know how about you, but I like to keep a few tweaks in my rc file (.bashrc in case of bash shell). However, with tmux the .bashrc file isn't read at all. After examining things a bit, I found out that tmux tries to read .bash_profile instead of .bashrc. I won't mention rules standing behind it here as they are quite complicated, I will show you a simple workaround instead. Adding this line: 
  1. source ~/.bashrc  
to .bash_profile solves the issue. 

Advanced Capabilities of tmux 

Scripting tmux 
My favourite pane layout often looks the same every time I use tmux, of course it depends on the type of work being done. For example, working on a project may require a pane with source code, second for running tests and third one for tailing logs. Setting these panes up is a perfect example of a dull task. Then it's not a surprise that in tmux it can be automated: 
  1. selectp -t 0 # select the first (0) pane  
  2. splitw -h -p 50 # split it into two halves  
  3.   
  4. selectp -t 1 # select the new, second (1) pane  
  5. splitw -v -p 50 # split it into two halves  
  6. selectp -t 0 # go back to the first pane  
These commands should be saved in a separate file, e.g. .tmux/dev. In order to be able to run it, you should point to it from the .tmux.conf file: 
  1. bind D source-file ~/.tmux/dev  
From now on, pressing the prefix (Ctrl+a) followed by D (it's an uppercase character in this example, so Shift is required) will execute commands located in the.tmux/dev file. It's also worth knowing that such file can do a little more than just opening the panes. It can also run commands inside them, for example: 
  1. splitw -h -p 50 'vim' # split current pane and run 'vim' command inside the new one  
Building your own scripting files won't take too much time and will pay off soon. 

Sharing Session 
All we've talked about so far is limited to a one-user session. As screen allows to share session, tmux is no worse. And setting things up is not too complicated. In order to share session on the same machine, you have to explicitly give tmux the path to the Unix socket which will be used through the session lifetime
$ tmux -S /tmp/our_socket

Then you have to give other users access to the newly created file: 
$ chmod 777 /tmp/our_socket

As expected, when a new user wants to join the session, he has to pass the socket path, so that tmux knows which session is about to be used: 
$ tmux -S /tmp/our_socket attach

Note that setting privileges to 777 is one of the dumbest things you can do, unless you fully trust your co-workers. You can also consider more sophisticated access control, SSH forwarding or give wemux a try. wemux is a set of scripts that makes sharing session easier and cleaner. 

Supplement 
tmux shortcuts & cheatsheet 
使用 Screen 指令操控 UNIX/Linux 終端機的教學與範例

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