有没有办法在不清除屏幕的情况下更换线条？

Question

printf "line one\n"
printf "line two\n"

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）。我试过这样的命令：

printf "line one\n"
printf "line two\r"

这不是我想要的，因为它替换了最后一行 line two，而不是 line one。

我想做什么：

printf "line one\n"
printf "line two\n"
sleep 0.5
somecode "line three"

我想要的输出：

line three
line two

Answer 1

这可以通过tput 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 line\n"
printf "line two\n"
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'

这将最初打印：

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

然后在休眠 0.5 秒后 tput rc 将导致光标在执行最后 2x printf 命令之前“向上”移动 2 行：

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：here

一些文档：here 和 here

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，试试这个代码：

#!/bin/bash

# print first line
printf "first line is long\n"
# print second line
printf "line 2\n"
sleep 1
# move cursor two steps UP
printf "\033[2A"
# print line 3 (without \n)
printf "line #3"
# clear rest of first line
# and move cursor two steps down
printf "\033[K\r\033[2B"

关于 ANSI 转义序列的更多信息：https://tldp.org/HOWTO/Bash-Prompt-HOWTO/c327.html