来自"strsep"的字符串标记不打印(seg错误) [英] String token from `strsep` not printing (seg fault)

问题描述

我正在使用一小段代码来测试较大(入门)程序的功能，但是在显示从字符串中拔出的令牌时遇到了问题.

I'm using with a smaller piece of code to test functionality for a larger (beginner) program, but I have a problem displaying the token I've pulled out of a string.

我发现并使用过:

#include <stdio.h>
#include <string.h>

int main()
{

char *string, *found;

string = strdup ("1/2/3");
printf("Original string: '%s'\n",string);

while ((found = strsep(&string,"/")) != NULL )
  printf ("%s\n",found);

return (0);
}

这很好用，一次将令牌作为字符串打印一个.

and this works fine, prints the tokens one at a time as strings.

然后，当我尝试移至用户输入的字符串时:

Then when I try and move to a user entered string:

#include <stdio.h>
#include <string.h>

int main()
{
  char string[13];
  char *found, *cp = string;

  fprintf(stderr, "\nEnter string: ");
  scanf("%12s",string);
  printf("Original string: '%s'\n",string);

  while((found =  strsep(&cp,"/,-")) != NULL )
    printf("Test 1"); /*To pinpoint where the seg fault arises*/
    printf("%s\n",found);

  return(0);
}

在printf("%s\n",found);行上出现段错误.我掌握了指针，数组和字符串的基础知识，但显然我缺少了一些东西，希望有人告诉我它是什么！

I get a seg fault on the printf("%s\n",found); line. I'm getting the hang of basics of pointers, arrays and strings, but clearly I'm missing something, and would love for someone to tell me what it is!

也-如果我更改printf("%s\n",found);的参数，例如到printf("%i\n",found);我得到了一些随机性，但总是正确的数量，例如如果输入1/2/3，我会得到三行垃圾，输入1111/2222会得到两行.我尝试了％c，％i，％d，％p，它们都执行相同的操作，但是出现了％s seg错误.

Also - if I change the argument of printf("%s\n",found); e.g. to printf("%i\n",found); I get some randomness returned, but always the correct amount, e.g. If I enter 1/2/3 I get three lines of junk, entering 1111/2222 gives two lines. I tried %c, %i, %d, %p and they all do the same, but %s seg faults.

我完全迷住了.

推荐答案

此段错误是因为您缺少while周围的括号.您将继续打印测试1"，直到strsep返回NULL，然后尝试打印该结果(和段错误).

The segfault is because you're missing braces around your while. You'll keep printing "Test 1" until strsep returns NULL, then you try to print that result (and segfault).

带有几个警告标记(可能是-Wall)，gcc可以在这里提供帮助:

With several warning flags (probably -Wall), gcc helps out here:

sep.c:13:3: warning: this ‘while’ clause does not guard... [-Wmisleading-indentation]
   while((found =  strsep(&cp,"/,-")) != NULL )
   ^~~~~
sep.c:15:5: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the ‘while’
     printf("%s\n",found);
     ^~~~~~

在while周围添加花括号，该程序将按预期工作:

With braces added around the while, the program works as expected:

./sep 

Enter string: abc/def
Original string: 'abc/def'
Test 1abc
Test 1def

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