Strtoul command

最新推荐文章于 2020-07-30 16:51:38 发布

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最新推荐文章于 2020-07-30 16:51:38 发布

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原文链接：https://yq.aliyun.com/articles/10543

本文介绍了 C 语言中的 strtoul 函数，该函数用于将字符串转换为无符号长整型数值。文章详细解释了函数参数的意义及返回值的情况，并通过一个示例程序展示了如何使用此函数。

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function

strtoul #include <stdlib.h>

unsigned long int strtoul (const char* str, char** endptr, int base);

Convert string to unsigned long integer

Parses the C-string str, interpreting its content as an integral number of the specified base, which is returned as an value of type unsigned long int.

This function operates like strtol to interpret the string, but produces numbers of type unsigned long int (see strtolfor details on the interpretation process).

Parameters

str

C-string containing the representation of an integral number.

endptr

Reference to an object of type char*, whose value is set by the function to the next character in str after the numerical value.
This parameter can also be a null pointer, in which case it is not used.

base

Numerical base (radix) that determines the valid characters and their interpretation.
If this is 0, the base used is determined by the format in the sequence (see strtol for details).

Return Value

On success, the function returns the converted integral number as an unsigned long int value.
If no valid conversion could be performed, a zero value is returned.
If the value read is out of the range of representable values by an unsigned long int, the function returns ULONG_MAX(defined in <climits>), and errno is set to ERANGE.

Example

/* strtoul example */
#include <stdio.h>      /* printf, NULL */
#include <stdlib.h>     /* strtoul */

int main ()
{
  char buffer [256];
  unsigned long ul;
  printf ("Enter an unsigned number: ");
  fgets (buffer, 256, stdin);
  ul = strtoul (buffer, NULL, 0);
  printf ("Value entered: %lu. Its double: %lu\n",ul,ul*2);
  return 0;
}

Edit & Run

Possible output:


Enter an unsigned number: 0x7ff
Value entered: 2047. Its double: 4094