为什么在外壳程序脚本中找不到lsof命令，但在Terminal中却能很好地工作

Question

我的shell脚本中的lsof命令无法正常工作，但在Terminal中可以正常工作。我已经设置了lsof命令的完整路径，但是总是抛出关于此的错误：

lsof: unacceptable port specification in: -i :
lsof 4.89
 latest revision: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/
 latest FAQ: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/FAQ
 latest man page: ftp://lsof.itap.purdue.edu/pub/tools/unix/lsof/lsof_man
 usage: [-?abhlnNoOPRtUvV] [+|-c c] [+|-d s] [+D D] [+|-f[cgG]]
 [-F [f]] [-g [s]] [-i [i]] [+|-L [l]] [+|-M] [-o [o]] [-p s]
 [+|-r [t]] [-s [p:s]] [-S [t]] [-T [t]] [-u s] [+|-w] [-x [fl]] [--] [names]
Use the ``-h'' option to get more help information.


function launchAnyproxy()
{
    cd ../..
    port=`/usr/sbin/lsof -t -i :8888`
    echo $port
    #port=`netstat -ln |grep '8888'`
    if [ ! -n "$port" ]; then
        anyproxy --intercept
    else
        echo "8888 is listening by other process"
    fi
}

launchAnyproxy