From: http://www.cclove.me/Enable_clear_command_on_cygwin.html

默认安装的cygwin的bash shell并没有clear命令，于是有些shell程序需要用到的时候就蛋疼了：

Katherine@cclove ~$ cls
-bash: cls: command not foundKatherine@cclove ~$ clear
-bash: clear: command not foundKatherine@cclove ~$ which cls
which: no cls in (/usr/local/bin:/usr/bin:/cygdrive/c/WINDOWS/system32:/cygdrive/c/WINDOWS:/cygdrive/c/WINDOWS/System32/Wbem:/cygdrive/c/Python27)Katherine@cclove ~$ which clear
which: no clear in (/usr/local/bin:/usr/bin:/cygdrive/c/WINDOWS/system32:/cygdrive/c/WINDOWS:/cygdrive/c/WINDOWS/System32/Wbem:/cygdrive/c/Python27)

搜索并装上ncurses就可以clear了：

Katherine@cclove ~$ which clear
/usr/bin/clearKatherine@cclove ~$ ldd /usr/bin/clearntdll.dll => /cygdrive/c/WINDOWS/system32/ntdll.dll (0x7c920000)kernel32.dll => /cygdrive/c/WINDOWS/system32/kernel32.dll (0x7c800000)cygwin1.dll => /usr/bin/cygwin1.dll (0x61000000)cyggcc_s-1.dll => /usr/bin/cyggcc_s-1.dll (0x6fcf0000)cygncurses-10.dll => /usr/bin/cygncurses-10.dll (0x6f9b0000)