bash 如何打印到同一行，覆盖上一行？
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How to print out to the same line, overriding previous line?
提问by nacho4d
Sometimes I see some commands in the terminal that print results to stdout but in the same line. For example wget prints an arrow like below:
有时我会在终端中看到一些命令将结果打印到标准输出，但在同一行中。例如 wget 打印如下箭头：
0[=> ]100%
0[ => ]100%
0[ => ]100%
0[ => ]100%
0[ =>]100%
but it is printed out to the same line so it looks like the arrow is moving. How can I achieve the same thing in my programs using bash or sh? Do I need to use other tools?
但它被打印到同一行，所以看起来箭头在移动。如何使用 bash 或 sh 在我的程序中实现相同的功能？我需要使用其他工具吗？
UPDATE:
更新：
I know I mentioned wget, which comes by default in linux, GNU based unices ... Is there a general approach that works on BSDs too? (like OSX) -> OK, If I use bash instead of sh then it works :)
我知道我提到了 wget，它在 linux 中默认出现，基于 GNU 的 unices ......是否有适用于 BSD 的通用方法？（如 OSX）-> 好的，如果我使用 bash 而不是 sh 那么它可以工作:)
回答by choroba
Use the special character \r. It returns to the beginning of the line without going to the next one.
使用特殊字符\r。它返回到行的开头而不去下一个。
for i in {1..10} ; do
echo -n '['
for ((j=0; j<i; j++)) ; do echo -n ' '; done
echo -n '=>'
for ((j=i; j<10; j++)) ; do echo -n ' '; done
echo -n "] $i"0% $'\r'
sleep 1
done
回答by fedorqui 'SO stop harming'
You can use \rfor this purpose:
您可以\r为此目的使用：
For example this will keep updating the current time in the same line:
例如，这将在同一行中不断更新当前时间：
while true; do echo -ne "$(date)\r"; done
回答by user1146332
You can also use ANSI/VT100 terminal escape sequencesto achieve this.
您也可以使用它ANSI/VT100 terminal escape sequences来实现这一点。
Here is a short example. Of course you can combine the printfstatements to one.
这是一个简短的例子。当然，您可以将这些printf语句合二为一。
#!/bin/bash
MAX=60
ARR=( $(eval echo {1..${MAX}}) )
for i in ${ARR[*]} ; do
# delete from the current position to the start of the line
printf "\e[2K"
# print '[' and place '=>' at the $i'th column
printf "[\e[%uC=>" ${i}
# place trailing ']' at the ($MAX+1-$i)'th column
printf "\e[%uC]" $((${MAX}+1-${i}))
# print trailing '100%' and move the cursor one row up
printf " 100%% \e[1A\n"
sleep 0.1
done
printf "\n"
With escape sequences you have the most control over your terminal screen.
使用转义序列，您可以最大程度地控制终端屏幕。
You can find an overview of possible sequences at [1].
您可以在 [ 1] 中找到可能序列的概述。
