建立eMbedded scripts

建構自己嵌入式系統的專案
寫一個scripts
#!/bin/sh

export PROJECT=eMbedded
export PRJROOT=/home/nelsonchung/${PROJECT}
export TARGET=i386-linux
export PREFIX=${PRJROOT}/tools
export TARGET_PREFIX=${PREFIX}/${TARGET}
export PATH=${PREFIX}/bin:${PATH}
cd ${PRJROOT}

sh是bash

但是為什麼用echo $PATH
卻沒有把上述的設定${PREFIX}/bin加入PATH
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/bin/X11:/usr/games