echo 转义字符输出
$ echo "a\tb\tc"
a\tb\tc
$ echo -e "a\tb\tc"
a b c
tr 用法
$ echo -e "a\tb\tc" | tr "\t" "-"
a-b-c
tr 删除 和 替换
$ echo '["a","b","c","d"]'
["a","b","c","d"]
$ echo '["a","b","c","d"]' | tr -d ']"[' | tr "," "\n"
a
b
c
d
printf vs echo 格式化输出
$ for i in $(seq 4); do printf '%s\n' $i;done
1
2
3
4
