C 格式的字符串 - 如何使用 sprintf 向字符串值添加前导零? [英] C formatted string - How to add leading zeros to string value using sprintf?
问题描述
我想在字符串的开头添加零.我正在使用格式说明符.我的输入字符串是 hello
我希望输出为 000hello
.
我知道如何对整数执行此操作.
int main(){国际我= 232;字符 str[21];sprintf(str,"%08d",i);printf("%s",str);返回0;}
<块引用>
输出将为 -- 00000232
如果我对字符串也这样做.
int main(){char i[]="你好";字符 str[21];sprintf(str,"%08s",i);printf("%s",str);返回0;}
<块引用>
OUTPUT 将是 - hello(前导 3 个空格)
为什么在字符串的情况下给空间而在整数的情况下给零?
如何使用 sprintf 向字符串值添加前导零?
使用 "%0*d%s"
在前面加上零.
"%0*d"
--> 0
零的最小宽度,*
从参数列表导出的宽度,d
打印一个 int
.
当字符串前面不需要零时,需要一个异常.
void PrependZeros(char *dest, const char *src, unsigned width) {size_t len = strlen(src);if (len >= width) strcpy(dest, src);else sprintf(dest, "%0*d%s", (int) (width - len), 0, src);}
<小时>
但我不认为 sprintf()
是适合这项工作的工具,代码如下.
//根据需要在前面加上0",从而产生一个 _minimal_ 宽度的字符串.void PrependZeros(char *dest, const char *src, unsigned minimum_width) {size_t len = strlen(src);size_t zeros = (len > minimum_width) ?0 : minimum_width - len;memset(dest, '0', 零);strcpy(dest + zeros, src);}
<小时>
void testw(const char *src, unsigned width) {字符 dest[100];PrependZeros(dest, src, width);printf("%u <%s>\n", width, dest);}int main() {for (无符号 w = 0; w <10; w++)testw("你好", w);for (无符号 w = 0; w <2; w++)testw("", w);}
输出
0 <你好>1 <你好>2 <你好>3 <你好>4 <你好>5 <你好>6 <0你好>7 <00你好>8 <000你好>9 <0000你好>0 <>1<0>
I want to add zeroes at the starting of a string. I am using format specifier.
My input string is hello
I want output as 000hello
.
I know how to do this for integer.
int main()
{
int i=232;
char str[21];
sprintf(str,"%08d",i);
printf("%s",str);
return 0;
}
OUTPUT will be -- 00000232
If I do the same for string.
int main()
{
char i[]="hello";
char str[21];
sprintf(str,"%08s",i);
printf("%s",str);
return 0;
}
OUTPUT will be - hello (with 3 leading space)
Why it is giving space in case of string and zero in case of integer?
How to add leading zeros to string value using sprintf?
Use "%0*d%s"
to prepend zeros.
"%0*d"
--> 0
min width of zeros, *
derived width from the argument list, d
print an int
.
An exception is needed when the string needs no zeros up front.
void PrependZeros(char *dest, const char *src, unsigned width) {
size_t len = strlen(src);
if (len >= width) strcpy(dest, src);
else sprintf(dest, "%0*d%s", (int) (width - len), 0, src);
}
Yet I do not think sprintf()
is the right tool for the job and would code as below.
// prepend "0" as needed resulting in a string of _minimal_ width.
void PrependZeros(char *dest, const char *src, unsigned minimal_width) {
size_t len = strlen(src);
size_t zeros = (len > minimal_width) ? 0 : minimal_width - len;
memset(dest, '0', zeros);
strcpy(dest + zeros, src);
}
void testw(const char *src, unsigned width) {
char dest[100];
PrependZeros(dest, src, width);
printf("%u <%s>\n", width, dest);
}
int main() {
for (unsigned w = 0; w < 10; w++)
testw("Hello", w);
for (unsigned w = 0; w < 2; w++)
testw("", w);
}
Output
0 <Hello>
1 <Hello>
2 <Hello>
3 <Hello>
4 <Hello>
5 <Hello>
6 <0Hello>
7 <00Hello>
8 <000Hello>
9 <0000Hello>
0 <>
1 <0>
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