bash – 这里的字符串添加换行符

看来这里的字符串是添加换行符.有没有方便的删除方法？

$string='test'
$echo -n $string | md5sum
098f6bcd4621d373cade4e832627b4f6  -
$echo $string | md5sum
d8e8fca2dc0f896fd7cb4cb0031ba249  -
$md5sum <<<"$string"
d8e8fca2dc0f896fd7cb4cb0031ba249  -

是的,你是对的：<<<添加一个尾随的新行. 你可以看到它：

$cat - <<< "hello" | od -c
0000000   h   e   l   l   o  \n
0000006

让我们将其与其他方法进行比较：

$echo "hello" | od -c
0000000   h   e   l   l   o  \n
0000006
$echo -n "hello" | od -c
0000000   h   e   l   l   o
0000005
$printf "hello" | od -c
0000000   h   e   l   l   o
0000005

所以我们有桌子：

| adds new line |
-------------------------|
printf   |      No       |
echo -n  |      No       |
echo     |      Yes      |
<<<      |      Yes      |

从Why does a bash here-string add a trailing newline char?开始：

Most commands expect text input. In the unix world,07001.
So in most cases a final newline is required. An especially common
case is to grab the output of a command with a command susbtitution,
process it in some way,then pass it to another command. The command
substitution strips final newlines; <<< puts one back.