Ubuntu 中shell程序的意思

1.ofileName= # old file name ，其中old file name被注释掉了吗？既然被注释了，那这句话的用处是什么？
2.while read line 是什么意思？
3.index=`expr ${index} + 1`，请问是什么意思？
4.if [ ${index} -eq 1 ]是什么意思？



function change()
{
ofileName= # old file name
nfileName= #new file name
ls -l > a.txt
index=0
while read line
do
index=`expr ${index} + 1`
if [ ${index} -eq 1 ] ; then
continue; # ignore the first line of 'ls -l'
fi
a=($line)
#echo ${a[8]} the 9th element of array is file name
#echo ${a[3]} # the 3rd element of array is owner name
ofileName=${a[8]}
pos=`expr index ${ofileName} "."` # pos = the . position in file name
if [ ${pos} -eq 0 ] ; then # if no . in filename then nfileName=oldName+[+owner+]
nfileName="${ofileName}[${a[3]}]"
else
owner="[${a[3]}]."
nfileName="${a[8]/./${owner}} " # substitute the . character to the"[owner]."
fi
echo "nfilename=${nfileName}"
changename ${ofileName}${nfileName} #call function changename to change file name to new file name
done<a.txt
}

1,2不知道
expr是计算,[ ]是test,-eq是相等...