C - 如何逐行讀取字符串？

Question

在我的C程序中，我有一個字符串，我希望一次處理一行，理想情況是將每行保存到另一個字符串中，按照所需字符串進行操作，然後重複。不過，我不知道這將如何實現。

我正在考慮使用sscanf。 sscanf中是否存在「讀取指針」，就像我從文件中讀取一樣？這樣做會是另一種選擇嗎？

Answer 1

這裏是你如何能有效地做到這一點，如果你被允許寫入到長字符串的例子：

#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; 
} 

如果你不允許寫入的長字符串，然後你會需要爲每行創建一個臨時字符串，以便使每行字符串NUL終止。像這樣：

#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; 
}