1/迭代每一行
while read line;
do
echo $line;
done < file.txt
cat file.txt | (while read line; do echo $line ;done )
2/迭代单词中的每一个单词
for word in $line;
do
echo $word;
done
3/迭代一个单词中的每一个字符
for ((i=0;i<${#word};i++)) #${#word}返回变量word的长度
do
echo ${word:i:1};
done