Tmux下Mutt没有重绘终端窗口的问题

现象: 使用mutt查看邮件, 连续查看下一封, 或者按q回退到邮件列表, 屏幕上字符会混乱, 也就是比如看到下一封邮件, 但是有些地方还是上一封的内容字符, 并没有完全重绘(redraw)窗口.

这个问题困扰了很长一段时间, 多次搜索无果, 找不到切入点.

这两天又试了下, 发现在tmux下运行mutt会有这个问题, 否则是正常的. Google “tmux mutt not flush” 搜出这篇回答: Tmux + mutt not redrawing

试了下, 果然是这个原因.

查看man tmux关于default-terminal的设置:

Set the default terminal for new windows created in this session - the default value of the TERM environment variable. For tmux to work correctly, this must be set to `screen' or a derivative of it.

这个是设置新建窗口的TERM环境变量, 默认是screen. 另外这里还强调了必须设置screen或它的衍生. 而我设置的是xterm-256color. 于是改为:

set -g default-terminal "screen-256color"

另外, tmux设置TERM是在加载~/.zshrc之前, 所以如果在~/.zsh中设置了TERM, 还要做一定的定制:

if [ -z "$TMUX" ] && [[ "$TERM" =~ "xterm" ]]; then
    if [ -e /usr/share/terminfo/*/xterm-256color ]; then
        echo "1"
        export TERM='xterm-256color'
    else
        echo "2"
        export TERM='xterm-color'
    fi
elif [ -n "$TMUX" ]; then
    if [ -e /usr/share/terminfo/*/screen-256color ]; then
        echo "3"
        export TERM='screen-256color'
    else
        echo "4"
        export TERM='screen'
    fi
fi

这里有两个地方说明下:

• $TMUX 环境变量, 在使用tmux后, 这个变量是一个路径值
• -e /usr/share/terminfo/*/xterm-256color, 在linux下, *这个其实是terminal type的首字母, 但是mac os下不是这样, 我原先设置的是-e /usr/share/terminfo/x/xterm-256color, 在mac下不工作.

如果shell配置中没有设置TERM, 则只需要配置tmux.conf即可.

问题解决, mutt查看邮件的闹心问题总算没了

( TL;DR

并且没有完全弄清楚, 可能会有理解错误的地方 )

tty, pty, pts: (man 4 xxx查看手册)

tty, Tele TYpewriter 是一个终端设备, 是硬件设备(如VT100 或由 内核仿真(如Ctrl+Alt+F1~F6, 虚拟控制台).

• A tty is a native terminal device, the backend is either hardware or kernel emulated.
• The TTY is a terminal that doesn’t require X or any program to exist, aka a Real Terminal. So you can use that terminal even when X fails to load. (kernel stuff)

pty, pts, pseudoterminal, 伪终端. 是由普通程序仿真出来, 如screen, ssh等. pty分为ptmx(master)和pts(slave).

• A pty (pseudo terminal device) is a terminal device which is emulated by an other program (example: xterm, screen, or ssh are such programs).
• In practice, pseudo-terminals are used for implementing terminal emulators such as xterm
• A PTS is a a Pseudo Terminal that needs a program to exist. You can launch several PTS in the same TTY. Both behaviors almost the same. (user stuff)

Linux/Mac 下按 w 可以看到登录情况以及terminal name:

# 这台机器是部署在虚拟机上
# tty1 是我直接在虚拟机终端输入帐号密码登录进去
# pts/0 是通过ssh登录上去
tankywoo ~ % w
 18:13:38 up 13 days,  6:08,  2 users,  load average: 0.02, 0.04, 0.05
USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
tankywoo tty1      17:59   14:05   0.36s  0.34s -zsh
tankywoo pts/0     17:41    0.00s  0.57s  0.00s w

参考:

• What is the difference between a TTY terminal and a PTS graphical terminal in Linux?
• Difference between pts and tty

terminal, console, terminal emulator, terminal multiplexer

terminal emulator, 终端仿真器.

• is a program that emulates a video terminal within some other display architecture.
• provides a standardised character based interface for text mode applications, it emulates the behavior of real or idealised hardware.

如基于X Window的xterm, KDE默认的terminal konsole, Mac下比自带更好用的iTerm2, Win下的 PuTTY和XShell.

这是一份完整的列表List of terminal emulators

terminal multiplexer, 终端复用器.

is a software application that can be used to multiplex several virtual consoles, allowing a user to access multiple separate terminal sessions inside a single terminal window or remote terminal session.

如系统自带的screen, Ubuntu下有名的Byobu, 以及tmux

关于console和terminal, 其实在日常的技术交流中, 这两个基本是等价的. 所以这里这里要是深究其区别, 并追溯历史原因, 是一件很蛋疼的事情.

• A terminal refers to a wrapper program which runs a shell. Decades ago, this was a physical device consisting of little more than a monitor and keyboard. As unix/linux systems added better multiprocessing and windowing systems, this terminal concept was abstracted into software. Now you have programs such as Gnome Terminal which launches a window in a Gnome windowing environment which will run a shell into which you can enter commands.
• The console is a special sort of terminal. Historically, the console was a single keyboard and monitor plugged into a dedicated serial console port on a computer used for direct communication at a low level with the operating system. Modern linux systems provide virtual consoles. These are accessed through key combinations (e.g. Alt+F1 or Ctrl+Alt+F1; the function key numbers different consoles) which are handled at low levels of the linux operating system – this means that there is no special service which needs to be installed and configured to run. Interacting with the console is also done using a shell program.

参考:

• What is the difference between a Console, Shell, Terminal, Terminal emulator, Terminal multiplexer, and a Window manager?
• What is the difference between shell, console, and terminal? 比较认可这篇的解释
• What is the difference between Terminal, Console, Shell, and Command Line? 这个帖子的一些回答都值得看看
• What is the exact difference between a ‘terminal’, a ‘shell’, a ‘tty’ and a ‘console’?
• console vs terminal

结合上面的这些说下自己的理解:

• tty和pty其实都可以总称tty(terminal).
• console是一个特殊的terminal.
• terminal一般用于指terminal emulator
• 直接显示器连服务器看到的是console

其实, 这块还是不纠结, 就当作一回事比较好, 基于历史原因, 曾经的terminal, console现在都software/virtual化了.

查了几个小时, 越看越晕.

关于$TERM环境变量, 定义terminal type (man 7 term):

• The environment variable TERM should normally contain the type name of the terminal, console or display-device type you are using. This information is critical for all screen-oriented programs, including your editor and mailer.
• associates the terminal you are using with a list of characteristics given in the terminfo(M) database. The characteristics tell the system how to interpret your terminal’s keys and how to display data on your terminal screen.
• The $TERM variable is for use by applications to take advantage of capabilities of that terminal.
• For example, if a program want’s to display colored text, it must first find out if the terminal you’re using supports colored text, and then if it does, how to do colored text.
• The way this works is that the system keeps a library of known terminals and their capabilities. On most systems this is in /usr/share/terminfo (there’s also termcap, but it’s legacy not used much any more).

toe 可以查看支持的terminal type

/usr/share/terminfo/ 是一个数据库, 存放是支持的terminal功能

infocmp <term type 1> <term type 2> 用于对比两个term的不同

参考:

• Which terminal type am I using? 解释的比较详细
• What’s the difference between various $TERM variables?
• Terminal emacs colors only work with TERM=xterm-256color

个人理解, terminal emulator 和 terminal type的关系, 有点类似Linux发行版和系统内核的关系. 比如guake和gnome-terminal这两个terminal emulator都是GNOME终端, terminal type可以是gnome一系的.

常规的万金油设置一般就是screen-*或者xterm-*

其它:

iTerm 在 Profiles -> Terminal -> Report Terminal Type 里可以设置终端仿真器的类型.

这个可以被shell配置(.basrc/.zshrc/…)中配置的$TERM环境变量覆盖.

• How does a Linux terminal work?
• Text-Terminal-HOWTO
• How are “xterm” and “screen” related?
• 系统变量TERM不知是用来干什么的？它的值有vt100，vt220等，这些值代表什么意思？