我想知道C中是否有办法覆盖已经打印过的现有值，而不是每次创建新行或只是在空格上移动。我需要从传感器获取实时数据，并希望它只是坐在那里并不断更新现有值而无需任何滚动。这可能吗？
更新：添加代码
#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdint.h>
#include <time.h>
#include <wiringPi.h>
#include <wiringPiI2C.h>
#define CTRL_REG1 0x20
#define CTRL_REG2 0x21
#define CTRL_REG3 0x22
#define CTRL_REG4 0x23
int fd;
short x = 0;
short y = 0;
short z = 0;
int main (){
fd = wiringPiI2CSetup(0x69); // I2C address of gyro
wiringPiI2CWriteReg8(fd, CTRL_REG1, 0x1F); //Turn on all axes, disable power down
wiringPiI2CWriteReg8(fd, CTRL_REG3, 0x08); //Enable control ready signal
wiringPiI2CWriteReg8(fd, CTRL_REG4, 0x80); // Set scale (500 deg/sec)
delay(200); // Wait to synchronize
void getGyroValues (){
int MSB, LSB;
LSB = wiringPiI2CReadReg8(fd, 0x28);
MSB = wiringPiI2CReadReg8(fd, 0x29);
x = ((MSB << 8) | LSB);
MSB = wiringPiI2CReadReg8(fd, 0x2B);
LSB = wiringPiI2CReadReg8(fd, 0x2A);
y = ((MSB << 8) | LSB);
MSB = wiringPiI2CReadReg8(fd, 0x2D);
LSB = wiringPiI2CReadReg8(fd, 0x2C);
z = ((MSB << 8) | LSB);
}
for (int i=0;i<10;i++){
getGyroValues();
// In following Divinding by 114 reduces noise
printf("Value of X is: %d\r", x/114);
// printf("Value of Y is: %d", y/114);
// printf("Value of Z is: %d\r", z/114);
int t = wiringPiI2CReadReg8(fd, 0x26);
t = (t*1.8)+32;//convert Celcius to Fareinheit
int a = wiringPiI2CReadReg8(fd,0x2B);
int b = wiringPiI2CReadReg8(fd,0x2A);
// printf("Y_L equals: %d\r", a);
// printf("Y_H equals: %d\r", b);
int c = wiringPiI2CReadReg8(fd,0x28);
int d = wiringPiI2CReadReg8(fd,0x29);
// printf("X_L equals: %d\r", c);
// printf("X_H equals: %d\r", d);
int e = wiringPiI2CReadReg8(fd,0x2C);
int f = wiringPiI2CReadReg8(fd,0x2D);
// printf("Z_L equals: %d\r", e);
// printf("Z_H equals: %d\r", f);
// printf("The temperature is: %d\r", t);
delay(2000);
}
};
答案 0 :(得分：23)
你正在寻找回车。在C中，那是\r。这将使光标返回到当前行的开头而不开始新行（换行）
答案 1 :(得分：18)
您应该像其他人所说的那样将\r添加到您的printf中。
此外，请确保刷新stdout，因为stdout流已缓冲＆amp;只会在到达换行符后显示缓冲区中的内容。
在你的情况下：
for (int i=0;i<10;i++){
//...
printf("\rValue of X is: %d", x/114);
fflush(stdout);
//...
}
答案 2 :(得分：5)
您可以使用“\ r”而不是“\ n”来完成。
答案 3 :(得分：2)
印在何处？
如果您正在将数据输出到标准输出，则通常无法返回并更改已编写的任何内容。如果您的标准输出定向到终端，您可以尝试输出\r字符，将光标移动到某些终端上的行的开头（效果取决于平台），以便后续输出行将覆盖以前印在那条线上的东西。这将产生旧数据被新数据替换的视觉效果。但是，这并不真正“替换”流中的旧数据，这意味着如果将标准输出重定向到文件，该文件将存储打印的所有内容。请记住，\r会强制您覆盖终端上的整行。
如果您将数据输出到文件，那么您可以使用fseek函数返回之前访问过的某个点并从那里“重新开始”，覆盖过程中的数据。
答案 4 :(得分：1)
您可以打印出与控制台屏幕一样多的换行符。这将有效地清除屏幕。
这是一个很好的link关于清算屏幕的不同方式。
答案 5 :(得分：1)
您是否测试了'\ b'字符（退格键）？也许取决于您的控制台。
答案 6 :(得分：-1)
请参阅示例代码以了解：
// Original code created by Daniel Cohen Gindi on 17/3/15.
//
// Copyright 2015 Daniel Cohen Gindi & Philipp Jahoda
// A port of MPAndroidChart for iOS
// Licensed under Apache License 2.0
//
// https://github.com/danielgindi/ios-charts
//
#import "LineChart2ViewController.h"
#import "ChartsDemo-Swift.h"
@interface LineChart2ViewController () <ChartViewDelegate>
@property (nonatomic, strong) IBOutlet LineChartView *chartView;
@property (nonatomic, strong) IBOutlet UISlider *sliderX;
@property (nonatomic, strong) IBOutlet UISlider *sliderY;
@property (nonatomic, strong) IBOutlet UITextField *sliderTextX;
@property (nonatomic, strong) IBOutlet UITextField *sliderTextY;
@end
@implementation LineChart2ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
self.title = @"Line compare";
_chartView.delegate = self;
_chartView.descriptionText = @"";
_chartView.noDataTextDescription = @"You need to provide data for the chart.";
_chartView.highlightEnabled = YES;
_chartView.dragEnabled = YES;
[_chartView setScaleEnabled:YES];
_chartView.drawGridBackgroundEnabled = NO;
_chartView.pinchZoomEnabled = YES;
_chartView.backgroundColor = [UIColor colorWithWhite:204/255.f alpha:1.f];
_chartView.legend.form = ChartLegendFormLine;
_chartView.legend.font = [UIFont fontWithName:@"HelveticaNeue-Light" size:11.f];
_chartView.legend.textColor = UIColor.whiteColor;
_chartView.legend.position = ChartLegendPositionBelowChartLeft;
ChartXAxis *xAxis = _chartView.xAxis;
xAxis.labelFont = [UIFont systemFontOfSize:12.f];
xAxis.labelTextColor = UIColor.whiteColor;
xAxis.drawGridLinesEnabled = NO;
xAxis.drawAxisLineEnabled = NO;
xAxis.spaceBetweenLabels = 1.0;
ChartYAxis *leftAxis = _chartView.leftAxis;
leftAxis.labelTextColor = [UIColor colorWithRed:51/255.f green:181/255.f blue:229/255.f alpha:1.f];
leftAxis.customAxisMax = 3;
leftAxis.drawGridLinesEnabled = YES;
ChartYAxis *rightAxis = _chartView.rightAxis;
rightAxis.labelTextColor = UIColor.redColor;
rightAxis.customAxisMax = 20.0;
rightAxis.startAtZeroEnabled = NO;
rightAxis.customAxisMin = 0.0;
rightAxis.drawGridLinesEnabled = NO;
[rightAxis setEnabled:NO];
[self setDataCount:20 range:4];
[_chartView animateWithXAxisDuration:2.5];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (void)setDataCount:(int)count range:(double)range
{
NSMutableArray *xVals = [[NSMutableArray alloc] init];
for (int i = 0; i < count; i++)
{
[xVals addObject:[@(i) stringValue]];
}
NSMutableArray *yVals = [[NSMutableArray alloc] init];
for (int i = 0; i < count; i++)
{
//double val = (double) (arc4random_uniform(range));
double val = 1.0;
[yVals addObject:[[ChartDataEntry alloc] initWithValue:val xIndex:i]];
}
LineChartDataSet *set1 = [[LineChartDataSet alloc] initWithYVals:yVals label:@"Line 1"];
set1.axisDependency = AxisDependencyLeft;
[set1 setColor:[UIColor colorWithRed:51/255.f green:181/255.f blue:229/255.f alpha:1.f]];
[set1 setCircleColor:UIColor.whiteColor];
set1.lineWidth = 2.0;
set1.circleRadius = 3.0;
set1.fillAlpha = 65/255.0;
set1.fillColor = [UIColor colorWithRed:51/255.f green:181/255.f blue:229/255.f alpha:1.f];
set1.highlightColor = [UIColor colorWithRed:244/255.f green:117/255.f blue:117/255.f alpha:1.f];
set1.drawCircleHoleEnabled = NO;
NSMutableArray *yVals2 = [[NSMutableArray alloc] init];
for (int i = 0; i < count; i++)
{
double val = 2.0;
ChartDataEntry * dataEntry = [[ChartDataEntry alloc] initWithValue:val xIndex:i];
[yVals2 addObject:dataEntry];
}
LineChartDataSet *set2 = [[LineChartDataSet alloc] initWithYVals:yVals2 label:@"Line 2"];
set2.axisDependency = AxisDependencyRight;
[set2 setColor:UIColor.redColor];
[set2 setCircleColor:UIColor.whiteColor];
set2.lineWidth = 2.0;
set2.circleRadius = 3.0;
set2.fillAlpha = 65/255.0;
set2.fillColor = UIColor.redColor;
set2.highlightColor = [UIColor colorWithRed:244/255.f green:117/255.f blue:117/255.f alpha:1.f];
set2.drawCircleHoleEnabled = NO;
NSMutableArray *yVals3 = [[NSMutableArray alloc] init];
for (int i = 0; i < count; i++)
{
double val = 3.0;
[yVals3 addObject:[[ChartDataEntry alloc] initWithValue:val xIndex:i]];
}
LineChartDataSet *set3 = [[LineChartDataSet alloc] initWithYVals:yVals3 label:@"Line 3"];
set3.axisDependency = AxisDependencyRight;
[set3 setColor:UIColor.blueColor];
[set3 setCircleColor:UIColor.whiteColor];
set3.lineWidth = 2.0;
set3.circleRadius = 3.0;
set3.fillAlpha = 65/255.0;
set3.fillColor = UIColor.blueColor;
set3.highlightColor = [UIColor colorWithRed:244/255.f green:117/255.f blue:117/255.f alpha:1.f];
set3.drawCircleHoleEnabled = NO;
NSMutableArray *dataSets = [[NSMutableArray alloc] init];
[dataSets addObject:set1];
[dataSets addObject:set2];
[dataSets addObject:set3];
LineChartData *data = [[LineChartData alloc] initWithXVals:xVals dataSets:dataSets];
[data setValueTextColor:UIColor.whiteColor];
[data setValueFont:[UIFont systemFontOfSize:9.f]];
_chartView.data = data;
}
答案 7 :(得分：-2)
除了以上答案外，\ r实际上是终端的代码。 c似乎没有提供一种方法来更改已放入stdout流中的程序。
#include<stdio.h>
int main(){
freopen("output.txt", "w", stdout);
printf("somthing");
printf("\r other thing");
}
在output.txt中，某些内容没有改变，这导致\ r对txt文件没有任何意义。 但是对于终端，\ r是有意义的。它可以处理格式并显示效果很好。
使用终端代码可以做一些有趣的事情。像下面一样
#include<iostream>
#include<bits/stdc++.h>
#include<unistd.h>
int main(){
std::string processBar[] {
"00%: [ ]",
"05%: [# ]",
"10%: [## ]",
"15%: [### ]",
"20%: [#### ]",
"25%: [##### ]",
"30%: [###### ]",
"35%: [####### ]",
"40%: [######## ]",
"45%: [######### ]",
"50%: [########## ]",
"55%: [########### ]",
"60%: [############ ]",
"65%: [############# ]",
"70%: [############## ]",
"75%: [############### ]",
"80%: [################ ]",
"85%: [################# ]",
"90%: [################### ]",
"95%: [#################### ]",
"100%:[#####################]",
};
int n = sizeof(processBar)/ sizeof(*processBar);
// pretty fanny
for(int i{0}; i<n; ++i){
fprintf(stdout, "\e[%d;1H \e[2K \r \a%s", i, processBar[i].c_str());
fflush(stdout);
sleep(1);
}
}