首先，找到源代码，在external/mksh/mkshrc,打开这个文件后会看到开头有如下脚本：

android4.2源码内容如下：

: ${TERM:=vt100} ${HOME:=/data} ${MKSH:=/system/bin/sh} ${HOSTNAME:=android}
: ${SHELL:=$MKSH} ${USER:=$(typeset x=$(id); x=${x#*\(}; print -r -- ${x%%\)*})}
if (( USER_ID )); then PS1='$'; else PS1='#'; fi

android5.0源码内容如下：

: ${TERM:=vt100} ${HOME:=/data} ${MKSH:=/system/bin/sh} ${HOSTNAME:=$(getprop ro.product.device)}
: ${SHELL:=$MKSH} ${USER:=$(typeset x=$(id); x=${x#*\(}; print -r -- ${x%%\)*})} ${HOSTNAME:=android}

: ${HOME:=/data}
: ${HOSTNAME:=$(getprop ro.product.device)}
: ${HOSTNAME:=android}
: ${MKSH:=/system/bin/sh}
: ${SHELL:=$MKSH}
: ${TERM:=xterm}
: ${TMPDIR:=/data/local/tmp}
: ${USER:=$(id -un)}