服务器评测
有时候会有这样的问题，当在公司服务器上打开了一个终端，做了很多事情，或正开着某个服务程序,下班回家了。
突然有事需要接入到服务器，如果用 ssh 连入，默认是一个新的终端，并不会打开你之前在公司的那个会话。而这时又需要继续在原来那个会话下操作。
今天发现 linux 下有一个 screen 命令，很有用. 在开启终端后，先运行一下 screen ,这样后续的操作都会被绑定到这个 screen 上。 而且可以在其它ssh 会话上使用 screen 命令打开旧的会话 ,继续未完成的事,甚至可以多个ssh连入同时共享一个会话，输入的命令会在所有共享ssh客户端同时显示，非常有趣.
例：
A连上服务器，并运行 screen
ssh user@server
screen
B连上服务器，打开A的会话
ssh user@server
screen -ls # 查看会话id
screen -rx xxxxx #打开指定的会话.
更多请查看 screen 的帮助:
Use: screen [-opts] [cmd [args]]
or: screen -r [host.tty]
Options:
-a Force all capabilities into each window’s termcap.
-A -[r|R] Adapt all windows to the new display width & height.
-c file Read configuration file instead of ‘.screenrc’.
-d (-r) Detach the elsewhere running screen (and reattach here).
-dmS name Start as daemon: Screen session in detached mode.
-D (-r) Detach and logout remote (and reattach here).
-D -RR Do whatever is needed to get a screen session.
-e xy Change command characters.
-f Flow control on, -fn = off, -fa = auto.
-h lines Set the size of the scrollback history buffer.
-i Interrupt output sooner when flow control is on.
-l Login mode on (update /var/run/utmp), -ln = off.
-list or -ls. Do nothing, just list our SockDir.
-L Turn on output logging.
-m ignore $STY variable, do create a new screen session.
-O Choose optimal output rather than exact vt100 emulation.
-p window Preselect the named window if it exists.
-q Quiet startup. Exits with non-zero return code if unsuccessful.
-r Reattach to a detached screen process.
-R Reattach if possible, otherwise start a new session.
-s shell Shell to execute rather than $SHELL.
-S sockname Name this session <pid>.sockname instead of <pid>.<tty>.<host>.
-t title Set title. (window’s name).
-T term Use term as $TERM for windows, rather than “screen”.
-U Tell screen to use UTF-8 encoding.
-v Print “Screen version 4.00.03jw4 (FAU) 2-May-06”.
-wipe Do nothing, just clean up SockDir.
-x Attach to a not detached screen. (Multi display mode).
-X Execute <cmd> as a screen command in the specified session.
