[英]How to print by output from the right hand side of the screen instead of the usual left hand side in C?
I am programming a game in which I need to create some blocks.我正在编写一个游戏,我需要在其中创建一些块。 I programmed that part perfectly, but the problem is that they need to aligned towards the right hand side of the screen as opposed to the usual left hand side.
我对该部分进行了完美编程,但问题是它们需要与屏幕的右侧对齐,而不是通常的左侧。 Now, I know the long approach of printing blanks to do so, but I was just curious if there is any shortcut to print the output from the right in C or C++?
现在,我知道打印空白的漫长方法,但我只是好奇是否有任何快捷方式可以从 C 或 C++ 的右侧打印 output?
If you are referring something similar to the Console stdout (C++), eg cout, You can use either this: 如果要引用类似于Console stdout(C ++)的名称,例如cout,则可以使用以下任一方法:
http://www.cplusplus.com/reference/ios/right/ http://www.cplusplus.com/reference/ios/right/
or the iomanip library allows you to have a number of text formatting capabilities. 或iomanip库允许您具有多种文本格式设置功能。 For example:
例如:
cout << setw(20) << setiosflags(ios::right) << "Hello World!" << endl;
http://www.cplusplus.com/reference/iomanip/ http://www.cplusplus.com/reference/iomanip/
Don't forget to #include <iomanip>
. 不要忘记
#include <iomanip>
。
Oh and please note that to align right, I believe you have to set width. 哦,请注意,要正确对齐,我相信您必须设置宽度。
Hope it helps. 希望能帮助到你。
First, figure out how many columns the screen has. 首先,找出屏幕上有多少列。 This depends on the platform you are programming for;
这取决于您要为其编程的平台。 I cannot help you because you did not specify the platform.
我没有帮助您,因为您没有指定平台。
For the actual printing, you can use printf
with a field-width specifier which right-aligns your text to the given field-width. 对于实际的打印,您可以将
printf
与字段宽度说明符配合使用,该说明符会将您的文本右对齐到给定的字段宽度。
For more complex cases, have a look at curses, a comprehensive library for terminal programming. 对于更复杂的情况,请查看curses,这是一个用于终端编程的综合库。
In most common Unix-alike platforms you can use the ioctl
system call: 在最常见的类似Unix的平台上,可以使用
ioctl
系统调用:
#include <sys/ioctl.h>
#include <stdio.h>
int main()
{
char *string = "Hello World";
struct winsize w;
ioctl(0, TIOCGWINSZ, &w);
printf("%*s\n", w.ws_col, string);
return 0;
}
As noted in other suggested answers, the solution really depends on the type of system on which the program runs, and more importantly what type of device which displays the result. 如其他建议的答案所述,解决方案实际上取决于程序在其上运行的系统的类型,更重要的是取决于显示结果的设备的类型。 The variations on alignment using formatting controls (as with printf or cout) are essentially the same as padding the output line yourself with blanks, but using a more elegant programming interface.
使用格式控制(如printf或cout)的对齐方式的变化与使用空白填充自己的输出行基本相同,但使用的是更优雅的编程界面。
Moving past those (since they do not appear to be what was requested), the type of display device is of interest. 越过那些(因为它们似乎不是所请求的),因此显示设备的类型是令人关注的。 Graphical displays universally permit one to place text anywhere on the (programmable) device.
图形显示普遍允许人们将文本放置在(可编程)设备上的任何位置。 However, character-cell devices such as a terminal make it a little harder.
但是,字符单元设备(例如终端)使其变得更难一点。 Any that you are likely to use on a POSIX system allow you to write text at the cursor position, and to change the position at which you write the text using cursor-addressing .
您可能在POSIX系统上使用的任何工具都允许您在光标位置写文本,并使用cursor-addressing更改您写文本的位置。 (Windows consoles provide an analogous interface, with different details -- since no system was specified, POSIX is what most people assume).
(Windows控制台提供了类似的界面,但具有不同的细节-由于未指定系统,因此大多数人都认为POSIX是必需的)。
With cursor-addressing, you could write a given string aligned at the right side of the screen by doing this: 使用游标寻址,您可以通过以下操作编写一个在屏幕右侧对齐的给定字符串:
W
. W
L
(actually you need the number of cells on the screen which it will use -- the length of a UTF-8 string in bytes differs from its width ). L
(实际上,您需要它在屏幕上使用的单元格数量-以字节为单位的UTF-8字符串的长度与其宽度不同)。 W - L
on the current row of the screen (counting from zero). W - L
(从零开始计数)。 Though not part of POSIX , the TIOCGWINSZ
feature is widely supported, and provides a way to get the screen width, eg, How to set the terminal's size? 尽管不是POSIX的一部分,但
TIOCGWINSZ
功能得到了广泛支持,并提供了一种获取屏幕宽度的方法,例如, 如何设置终端的尺寸? . 。 (Some systems support a similar call with the
TIOCGSIZE
symbol, as noted in Getting terminal width in C? ). (某些系统使用
TIOCGSIZE
符号支持类似的调用,如在C中获取终端宽度中所述 )。
Rather than move the cursor along the line by writing blanks, one may choose fewer characters in a control sequence . 与其通过写空格沿行移动光标,不如在控制序列中选择更少的字符。 For moving the cursor, there are choices:
要移动光标,有以下选择:
HPA
(horizontal position, absolute). HPA
的控制序列(水平位置,绝对值)。 Not recommended but documentation is available, eg, in Linux's console_codes manual page, or XTerm Control Sequences . use termcap to ask if the terminal supports HPA
(called "ch"
in termcaps) or use CUF
(cursor-forward) with a parameter (but that requires you to know where you are ). 使用termcap询问终端是否支持
HPA
(在termcaps中称为"ch"
)或使用带有参数的CUF
(光标向前)(但这要求您知道您的位置 )。 Supposing that the terminal supports HPA
, your program would do something like 假设终端支持
HPA
,您的程序将执行以下操作
char *hpa = tgetstr("cm", &areap); tgoto(hpa, W - L, 0); puts(mystring);
use curses , and let it decide how to go to the right place: 使用curses ,让它决定如何去正确的地方:
int y, x; getyx(stdscr, y, x); move(y, WL); addstr(mystring);
the following, some of the info found at: <http://wiki.bash-hackers.org/scripting/terminalcodes>
should greatly help you with handling the screen/cursor activities.
General useful ASCII codes
The Ctrl-Key representation is simply associating the non-printable characters from ASCII code 1 with the printable (letter) characters from ASCII code 65 ("A"). ASCII code 1 would be ^A (Ctrl-A), while ASCII code 7 (BEL) would be ^G (Ctrl-G). This is a common representation (and input method) and historically comes from one of the VT series of terminals.
Name decimal octal hex C-escape Ctrl-Key Description
BEL 7 007 0x07 \a ^G Terminal bell
BS 8 010 0x08 \b ^H Backspace
HT 9 011 0x09 \t ^I Horizontal TAB
LF 10 012 0x0A \n ^J Linefeed (newline)
VT 11 013 0x0B \v ^K Vertical TAB
FF 12 014 0x0C \f ^L Formfeed (also: New page NP)
CR 13 015 0x0D \r ^M Carriage return
ESC 27 033 0x1B <none> ^[ Escape character
DEL 127 177 0x7F <none> <none> Delete character
Cursor handling
ANSI terminfo equivalent Description
[ <X> ; <Y> H
[ <X> ; <Y> f cup <X> <Y> Home-positioning to X and Y coordinates
:!: it seems that ANSI takes 1-1 as root while tput takes 0-0
[ H home Home-positioning to root (0-0)
7 sc Save current cursor position
8 rc Restore current cursor position
:?: most likely a normal code like \b cub1 move left one space (backspace)
VT100 [ ? 25 l civis switch cursor invisible
VT100 [ ? 25 h cvvis switch cursor visible
Erasing text
ANSI terminfo equivalent Description
[ K
[ 0 K el Clear line from current cursor position to end of line
[ 1 K el1 Clear line from beginning to current cursor position
[ 2 K el2:?: Clear whole line (cursor position unchanged)
General text attributes
ANSI terminfo equivalent Description
[ 0 m sgr0 Reset all attributes
[ 1 m bold Set "bright" attribute
[ 2 m dim Set "dim" attribute
[ 4 m set smul unset rmul :?: Set "underscore" (underlined text) attribute
[ 5 m blink Set "blink" attribute
[ 7 m rev Set "reverse" attribute
[ 8 m invis Set "hidden" attribute
Foreground coloring
ANSI terminfo equivalent Description
[ 3 0 m setaf 0 Set foreground to color #0 - black
[ 3 1 m setaf 1 Set foreground to color #1 - red
[ 3 2 m setaf 2 Set foreground to color #2 - green
[ 3 3 m setaf 3 Set foreground to color #3 - yellow
[ 3 4 m setaf 4 Set foreground to color #4 - blue
[ 3 5 m setaf 5 Set foreground to color #5 - magenta
[ 3 6 m setaf 6 Set foreground to color #6 - cyan
[ 3 7 m setaf 7 Set foreground to color #7 - white
[ 3 9 m setaf 9 Set default color as foreground color
Background coloring
ANSI terminfo equivalent Description
[ 4 0 m setab 0 Set background to color #0 - black
[ 4 1 m setab 1 Set background to color #1 - red
[ 4 2 m setab 2 Set background to color #2 - green
[ 4 3 m setab 3 Set background to color #3 - yellow
[ 4 4 m setab 4 Set background to color #4 - blue
[ 4 5 m setab 5 Set background to color #5 - magenta
[ 4 6 m setab 6 Set background to color #6 - cyan
[ 4 7 m setab 7 Set background to color #7 - white
[ 4 9 m setaf 9 Set default color as background color
Misc codes
Save/restore screen
Used capabilities: smcup, rmcup
You've undoubtedly already encountered programs that restore the terminal contents after they do their work (like vim). This can be done by the following commands:
# save, clear screen
tput smcup
clear
# example "application" follows...
read -n1 -p "Press any key to continue..."
# example "application" ends here
# restore
tput rmcup
These features require that certain capabilities exist in your termcap/terminfo. While xterm and most of its clones (rxvt, urxvt, etc) will support the instructions, your operating system may not include references to them in its default xterm profile. (FreeBSD, in particular, falls into this category.) If `tput smcup` appears to do nothing for you, and you don't want to modify your system termcap/terminfo data, and you KNOW that you are using a compatible xterm application, the following may be work for you:
echo -e '\033[?47h' # save screen
echo -e '\033[?47l' # restore screen
The following is more specific to cursor placement:
<http://tldp.org/HOWTO/Bash-Prompt-HOWTO/x361.html>
- Position the Cursor:
\033[<L>;<C>H
Or
\033[<L>;<C>f
puts the cursor at line L and column C.
- Move the cursor up N lines:
\033[<N>A
- Move the cursor down N lines:
\033[<N>B
- Move the cursor forward N columns:
\033[<N>C
- Move the cursor backward N columns:
\033[<N>D
- Clear the screen, move to (0,0):
\033[2J
- Erase to end of line:
\033[K
- Save cursor position:
\033[s
- Restore cursor position:
\033[u
Lets say that we are trying to print '*' from the right.And in total we want to print 10 stars.For better visualization I will be using Sleep(1000)to see the printing of the stars in action.Here's what the sample program will look like:假设我们正在尝试从右侧打印“*”。我们总共要打印 10 颗星。为了更好地可视化,我将使用 Sleep(1000) 来查看正在打印的星星。这是示例程序将如下所示:
#include<iostream>
#include<iomanip>
#include<Windows.h>
using namespace std;
int main() {
int n=10;
for(int i=n;i>0;i--){
cout<<setw(i+1)<<"*\r"<<flush;
Sleep(1000);
}
return 0;
}
Here the setw() function from the "iomanip" library is used to set the width of the string to be printed.The additional "+1" in "i+1" is used to account for the character "\r" which is an escape character in c++ called the "carriage return" which tells the terminal emulator to move the cursor to the start of the line, not to the next line, like \n.这里使用“iomanip”库中的 setw() function 来设置要打印的字符串的宽度。“i+1”中的附加“+1”用于说明字符“\r”,即c++ 中的转义字符称为“回车”,它告诉终端仿真器将 cursor 移动到行的开头,而不是下一行,例如 \n。
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