C - 如何逐行读取字符串？

Question

在我的 C 程序中，我有一个字符串，我想一次处理一行，理想情况下是将每一行保存到另一个字符串中，对所述字符串执行我想要的操作，然后重复。不过，我不知道这将如何实现。

我正在考虑使用 sscanf。 sscanf 中是否存在“读取指针”，就像我从文件中读取时一样？这样做的另一种选择是什么？

Answer 1

如果允许您写入长字符串，下面是一个如何高效执行此操作的示例:

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

int main(int argc, char ** argv)
{
   char longString[] = "This is a long string.\nIt has multiple lines of text in it.\nWe want to examine each of these lines separately.\nSo we will do that.";
   char * curLine = longString;
   while(curLine)
   {
      char * nextLine = strchr(curLine, '\n');
      if (nextLine) *nextLine = '\0';  // temporarily terminate the current line
      printf("curLine=[%s]\n", curLine);
      if (nextLine) *nextLine = '\n';  // then restore newline-char, just to be tidy    
      curLine = nextLine ? (nextLine+1) : NULL;
   }
   return 0;
}

如果您不允许写入长字符串，那么您需要为每一行创建一个临时字符串，以使每行字符串 NUL 终止。像这样:

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

int main(int argc, char ** argv)
{
   const char longString[] = "This is a long string.\nIt has multiple lines of text in it.\nWe want to examine each of these lines separately.\nSo we will do that.";
   const char * curLine = longString;
   while(curLine)
   {
      const char * nextLine = strchr(curLine, '\n');
      int curLineLen = nextLine ? (nextLine-curLine) : strlen(curLine);
      char * tempStr = (char *) malloc(curLineLen+1);
      if (tempStr)
      {
         memcpy(tempStr, curLine, curLineLen);
         tempStr[curLineLen] = '\0';  // NUL-terminate!
         printf("tempStr=[%s]\n", tempStr);
         free(tempStr);
      }
      else printf("malloc() failed!?\n");

      curLine = nextLine ? (nextLine+1) : NULL;
   }
   return 0;
}