要来的一个linux命令提示符的配置，一切为了得瑟

PROMPT_MAXPWDLEN=20 # The most characters to be shown.
PROMPT_HIDDENPREFIX=... # Prefix when hiding some characters.
PROMPT_UPDATE(){
lastcmd=1
if [ $1 = 0 ]; then
lastcmd_indicator='(^_^)'
PSCOLOR='[32;1m'
else
lastcmd_indicator='(@_@)'
PSCOLOR='[31;1m'
fi
if [ ${#PWD} -ge $((${PROMPT_MAXPWDLEN}+${#PROMPT_HIDDENPREFIX})) ]; then
PWDSHORT="${PROMPT_HIDDENPREFIX}$(pwd|sed -e "s|^.\{$((${#PWD}-${PROMPT_MAXPWDLEN}))\}||g;s|[^/]*/|/|;")"
else
PWDSHORT="${PWD}"
fi
echo -ne "\033]0;$(hostname -s):${PWDSHORT}\007"
PS1='${lastcmd:+\[\e${PSCOLOR}\]$lastcmd_indicator\[\e[m\] }\[\e[33;1m\][\!] \[\e[0;36m\]\u\[\e${PSCOLOR}\]@\[\e[0;32m\]\h\[\e${PSCOLOR}\]:\[\e[01;34m\]${PWDSHORT}\[\e[00m\]\$ '
}
PROMPT_COMMAND='PROMPT_UPDATE $?'

# set a fancy prompt (non-color, unless we know we "want" color).
case "$TERM" in
xterm-*color)
PSCOLOR='[00m'
# set PS1 for system PROMPT_COMMAND unusable
PS1='${lastcmd:+\[\e${PSCOLOR}\]$lastcmd_indicator\[\e[m\] }\[\e[33;1m\][\!] \[\e[0;36m\]\u\[\e${PSCOLOR}\]@\[\e[0;32m\]\h\[\e${PSCOLOR}\]:\[\e[01;34m\]\w\[\e[00m\]\$ '
;;
*)
PS1='[\!] \u@\h:\w\$ '
;;
esac