在C中带有前导零的printf [英] printf with leading zeros in C

问题描述

我有一个浮点数，例如 4917.24 。我想打印它始终有小数点前五个字符，前导零，然后三位小数点后。

我试过 printf（％05.3f，n）在我正在使用的嵌入式系统上，但它打印 ***** 。格式说明符是否正确？

解决方案

格式说明符不正确。从我的机器上的 printf（）手册页：

0 表示零填充应该是零的 0 使用而不是空白填充。如果 - ，则会覆盖 0 两者都被使用;

字段宽度：
一个指定字段宽度的可选数字字符串;如果输出字符串的字符数少于字段宽度，则在左侧（或右侧，如果已经给出了左侧调整指示符）填充字段宽度（注意，前导零是标记，但嵌入的零是字段宽度的一部分）;

精度：一个可选的期间' 。 ，然后是一个可选的数字字符串，用于指定小数点后面出现的位数， e 和 f 格式从字符串打印的最大字符数;如果数字字符串丢失，精度被视为零;

对于您的情况，您的格式将是％09.3f ：

  #include< stdio.h> 
 $ b $ int main（int argc，char ** argv）
 {
 printf（％09.3f\，4917.24）; 
返回0; 
 
 
 
 $ b $ p $输出：
 
 
  $ make testapp 
 cc testapp.c -o testapp 
 $ ./testapp 
 04917.240 
  
请注意，这个答案的条件是嵌入式系统有一个符合标准的 printf（）对于这些细节 - 许多嵌入式环境没有这样的实现。
 
I have a floating point number such as 4917.24. I'd like to print it to always have five characters before the decimal point, with leading zeros, then three digits after the decimal place.

I tried printf("%05.3f", n) on the embedded system I'm using, but it prints *****. Do I have the format specifier correct?
解决方案
Your format specifier is incorrect.  From the printf() man page on my machine:

  
0 A zero '0' character indicating that zero-padding should be used rather than blank-padding.  A '-' overrides a '0' if both are used;
  
  
Field Width:
  An optional digit string specifying a field width; if the output string has fewer characters than the field width it will be blank-padded on the left (or right, if the left-adjustment indicator has been given) to make up the field width (note that a leading zero is a flag, but an embedded zero is part of a field width);
  
  
Precision: An optional period, '.', followed by an optional digit string giving a precision which specifies the number of digits to appear after the decimal point, for e and f formats, or the maximum number of characters to be printed from a string; if the digit string is missing, the precision is treated as zero;
For your case, your format would be %09.3f:
#include <stdio.h>

int main(int argc, char **argv)
{
  printf("%09.3f\n", 4917.24);
  return 0;
}
Output:
$ make testapp
cc     testapp.c   -o testapp
$ ./testapp 
04917.240
Note that this answer is conditional on your embedded system having a printf() implementation that is standard-compliant for these details - many embedded environments do not have such an implementation.

                        
这篇关于在C中带有前导零的printf的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！