在特定行文件替換詞，用c

Question

在一個文件中我有幾行，像這樣：

The procedure at A1 is complete The procedure at B132 is incomplete The procedure at C45 is incomplete The procedure at D2 is complete

如果我知道，我想在3線改變的程序，向X4534

The procedure at C45 is incomplete 到 The procedure at X4534 is incomplete

什麼是一個簡單的方法來做到這一點？

我已經看過了fseek功能，我想我可以循環播放，直到我打了所需的行，勇往直前18位，和fwrite有，但「不完整」的文本仍然需要

Answer 1

對於這種類型的替換（要替換的字符串的長度和替換字符串的長度是不同的長度），您通常需要從一個文件讀取數據，並將已更改的數據寫入其他文件。

您可以逐行閱讀文件，然後使用sscanf()來確定該行是否需要更換。

例如：

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

int main() 
{ 
    FILE *input = fopen("in.txt", "r"); 
    FILE *output = fopen("out.txt", "w"); 

    char target[] = "C45"; 
    char replacement[] = "X4534"; 
    char lineBuffer[100]; 

    while (fgets(lineBuffer, sizeof lineBuffer, input) != NULL) 
    { 
     char procedure[10]; 

     if (sscanf(lineBuffer, "The procedure at %9s", procedure) == 1) 
     { 
      if (strcmp(procedure, target) == 0) 
      { 
       // if we get here, then the line matched the format we're 
       // looking for and we can therefore write our replacement 
       // line instead. 
       fprintf(output, "The procedure at %s is incomplete\n", replacement); 
       continue; 
      } 
     } 

     // if we get to this point, then the line didn't match the format 
     // or the procedure didn't match the one we're looking for, so we 
     // just output the line as it is. 
     fputs(lineBuffer, output); 
    } 

    fclose(input); 
    fclose(output); 
} 

上面的代碼應該給你一個什麼樣的介入了一些想法。一旦你已經out.txt保存，您可以使用標準的C函數rename()，例如：

rename("out.txt", "in.txt");