函数strtok造成段错误，但不是在通过code步骤 [英] strtok causing segfault but not when step through code

问题描述

我是新的C，我试图分裂日期/时间字符串转换成不同的变量。然而，当我通过GDB线code。通过行一步，它的工作原理，但是，当我让它通过正常没有它赛格故障断点运行，我不明白为什么。

I am new to C and I am trying to split a date/time string into separate variables. However, when I step through the code in gdb line by line, it works, however, when I let it run through normally without breakpoints it seg faults and I can't see why.

下面是code：

char * dateTimeString = "2011/04/16 00:00";
char dateVar[11];
char timeVar[6];

if (splitTimeAndDateString(dateVar, timeVar, dateTimeString))
{
    exit(1);
}

printf("Date: %s\tTime: %s\n", dateVar, timeVar);

下面是函数

int splitTimeAndDateString(char date[11], char time[6], char * dateString)
{
    char *token;
    token = strtok(dateString, " ");
    int i = 0;
    while (token != NULL)
    {
        if (i == 0)
        {
            strcpy(date, token);
        }
        else if (i == 1)
        {
            strcpy(time, token);
        }
        else
        {
            printf("Overrun date time string\n");
            return 1;
        }
        token = strtok(NULL, " ");
        i++;
    }
    return 0;
}

感谢您的帮助，您可以提供。

Thanks for any help you can provide.

推荐答案

的的strtok（）函数修改，你要分析，并更换所有的分隔符字符串 \\ 0 NUL符号。

The strtok() function modifies string that you wants to parse, and replace all delimiters with \0 nul symbol.

阅读：的char * strtok的（字符*海峡，为const char *分隔符）;

海峡结果
   C字符串截断。结果
   注意，这个字符串的内容
  被修改并分解成较小的字符串（令牌）。 Alternativelly，
  空指针可以指定，在这种情况下，功能继续
  扫描其中previous成功调用该函数结束了。

str
C string to truncate.
Notice that the contents of this string are modified and broken into smaller strings (tokens). Alternativelly, a null pointer may be specified, in which case the function continues scanning where a previous successful call to the function ended.

在您的code：

 strtok(dateString, " "); 
           ^
           |  is a constant string literal 

dateString 点2011年4月16日00:00一个常量字符串，并且通过使用的strtok（）您code试图写只读存储器 - 这是非法的，这引起了分段错误。

dateString points to "2011/04/16 00:00" a constant string literal, and by using strtok() your code trying to write on read-only memory - that is illegal and this caused segmentation fault.

阅读<一href=\"http://stackoverflow.com/questions/17104953/c-strtok-split-string-into-tokens-but-keep-old-data-unaltered/17104999#17104999\">linked答案图了解：如何的strtok（）作品？

Read this linked answer for diagram to understand: how strtok() works?

编辑：

@： 的char * strtok的（字符*海峡，为const char *分隔符）; 在给定的code例如， STR 是一个数组，而不是常量字符串。它的声明：

@: char * strtok ( char * str, const char * delimiters ); In given code example, str is an array, not constant string literal. Its declaration:

char str[] ="- This, a sample string.";

下面海峡[] 被终止的字符数组的NUL，与字符串初始化其长度等于指定字符串的大小。您可以更改的海峡[] 例如内容海峡[I] ='A'是一个有效的操作。

Here str[] is an nul terminated array of chars, that initialized with string and its length is equals to size of the assigned string. You can change the content of str[] e.g. str[i] = 'A' is a valid operation.

而在你的code：

char * dateTimeString = "2011/04/16 00:00"; 

dateTimeString 是指向字符串是不可修改的如 dateTimeString [I] ='A'是一个非法操作这个时候。

dateTimeString is pointer to string literal that is not modifiable e.g dateTimeString[i] = 'A' is an illegal operation this time.

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