把一个文档前五行中包含字母的行删掉，同时删除6到10行包含的所有字母
测试文件内容类似：
1fffff
2222222
34545-=-93
4aaaAa
555555~#$%
6dfd444
7545454dfsdf
8888888
9999999A
10erewr
11gdfgfd888
1256456dgfd
代码：
方法1：
#!/bin/bash
sum=$(cat ./txt/delchar.txt | wc -l)
echo total:${sum}
head -5 ./txt/delchar.txt | sed '/[a-zA-Z]/d' > ./txt/delchar1.txt
head -10 ./txt/delchar.txt | tail -5 | sed 's/[a-zA-Z]//g' >> ./txt/delchar1.txt
let lastpart=sum-10
tail -${lastpart} ./txt/delchar.txt >> ./txt/delchar1.txt
方法2：
#!/bin/bash
> ./txt/delchar2.txt
i=1
while read line
do
if [ $i -le 5 ]; then
echo $line |sed '/[a-zA-Z]/d' >> ./txt/delchar2.txt
elif [ $i -le 10 ] && [ $i -gt 5 ]; then
echo $line
echo $line |sed 's/[a-zA-Z]//g' >> ./txt/delchar2.txt
else
echo $line >> ./txt/delchar2.txt
fi
let i=i+1
done < ./txt/delchar.txt
