添加PATH环境变量：
-------------------------------------------------------
[root@localhost u-boot-sh4]#export PATH=/opt/STM/STLinux-2.3/devkit/sh4/bin:$PATH
查看PATH环境变量：
-------------------------------------------------------
[root@localhost u-boot-sh4]#echo $PATH
/usr/kerberos/sbin:/usr/kerberos/bin:/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin