有没有办法在不清除屏幕的情况下更换线路

Question

printf "line onen"
printf "line twon"

在这些打印输出之后，我想替换第一行并打印其他内容(不使用clear(。我尝试过以下命令：

printf "line onen"
printf "line twor"

这不是我想要的，因为它取代了最后一行line two，而不是line one。

我想做的事：

printf "line onen"
printf "line twon"
sleep 0.5
somecode "line three"

我想要的输出：

line three
line two

Answer 1

这可以用tput来完成，例如：

EraseToEOL=$(tput el)                 # save control code for 'erase to end of line'
tput sc                               # save pointer to current terminal line
printf "line one - a long linen"
printf "line twon"
sleep 0.5
tput rc                               # return cursor to last cursor savepoint (`tput sc`)
printf "line three${EraseToEOL}n"    # print over `line one - a long line`; print `$EraseToEOL` to clear rest of line (in case previous line was longer than `line three`)
printf "n"                           # skip over 'line two'

这将首先打印：

line one - a long line                # `tput sc` will point to this line
line two
<cursor>                              # cursor is left sitting on this line

然后在睡眠0.5秒后，tput rc将导致光标向上移动2行，然后执行最后2个printf命令：

line three                            # old 'line one - a long line` is overwritten
line two                              # `printf "n"` won't print anything new on this line so the old contents won't be overwritten, while the cursor will be moved to the next line
<cursor>                              # cursor is left sitting on this line

另一个例子：这里是

一些文档：此处和此处

Answer 2

您可以通过打印特殊的转义序列在bash脚本中移动光标，请尝试以下代码：

#!/bin/bash
# print first line
printf "first line is longn"
# print second line
printf "line 2n"
sleep 1
# move cursor two steps UP
printf "33[2A"
# print line 3 (without n)
printf "line #3"
# clear rest of first line
# and move cursor two steps down
printf "33[Kr33[2B"

有关ANSI转义序列的详细信息：https://tldp.org/HOWTO/Bash-Prompt-HOWTO/c327.html