如何在c中写入特定的文件行?

所以我有一个项目,我正在创建一个允许用户写入文件的程序,如下所示:

#include  #include  FILE *fd; FILE *fw; struct store { char Word[512]; char NWord[512]; } stock; struct store2 { char Definition[512]; } stock2; char done='y'; int count=1; int c=0; int d=0; int main(void) { fw=fopen("Test Z W.txt","w"); fd=fopen("Test Z D.txt","w"); do { printf("Word %d: ",count); gets(stock.Word); while((c= getchar()) != '\n' && c != EOF); printf("Definition %d: ",count); gets(stock2.Definition); while((c= getchar()) != '\n' && c != EOF); fprintf(fw,"%s\n", stock.Word); fprintf(fd,"%s\n", stock2.Definition); count=count+1; system("cls"); } while (count<11); fclose(fd); fclose(fw); return 0; } 

这段代码很好,但是,我想扩展它,以便有一个选项来编辑一个选定的行,而不是擦除整个文件并再次写入所有内容。

我所要做的就是使用如何在C中写入txt文件的特定行?

这是不是很有帮助,因为我无法回答并将其导入我的代码,无论哪种方式,我需要的是一个错误,如下面的错误,可以很容易地修复。

  1 2 Three 4 5 6 7 8 9 10 

将自动询问用户他们想要编辑哪一行。

 #include  int main() { FILE *fp,*fc; int lineNum; //stores line number which should be edited. int count=0; //count number lines in source file. int ch; //temporary place to store character of source file(one at a time). int edited=0; //0=false and 1=true int t; //temporary place to store input which you want to be replaced with error in text file. fp=fopen("source.txt","r"); fc=fopen("target.txt","w"); if(fp==NULL||fc==NULL) { printf("\nError...cannot open/create files"); return 1; } printf("\nEnter Line Number Which You Want 2 edit: "); scanf("%d",&lineNum); while((ch=fgetc(fp))!=EOF) { if(ch=='\n') //counts number of lines count++; if(count==lineNum-1 && edited==0) //if specific line(error line) is found and that line is still not edited. More Explanation:- If we want to edit 3rd line than we should start writing at the end of 2nd line(hence count==lineNum-1) and edited==0 means that error line is still not edited. { printf("\nEnter input to store at line %d:",lineNum); scanf(" %c",&t); //You can replace this statement with any input operation which you want to replace it with the error line. if(count==0) //if its the first line to edit.. fprintf(fc,"%s\n",t) //watch closely,no '\n' before %s,This will copy without creating a extra newline in beginning of new file. else fprintf(fc,"\n%s\n",t); //stores input at error line in file fc(target.txt) from variable t. edited=1; //this prevents loop to execute more than once(as error is already edited),so there will be no need to execute this loop till the end of program while( (ch=fgetc(fp))!=EOF ) //Actually this loop will skips the existing line in source.txt(see below) { //we want to skip this line because this is error line. if(ch=='\n')//this will break when next new line(after error line is skipped) is found. break; } } else fprintf(fc,"%c",ch); } fclose(fp); fclose(fc); if(edited==1) printf("\nCongrates...Error Edited Successfully."); else printf("\nLine Not Found"); return 0; } 

这个程序将打开一个源文件( 可能有错误 ,我称之为source.txt *)并继续逐个字符地读取它并写入新文件(target.txt)直到找到(EOF)。但它会停在特定行将要求用户在新文本文件(target.txt)中输入一些将代替错误(源文件中的错误行)写入的数据。

所以最后你会得到target.txt文件没有错误。 打开并检查它。

在这个程序中,我假设我们只想在第3行替换单个字符。但是你可以改变这个操作来用字符串,浮点数或整数等替换它。

这是输出: –

输入您想要的行号2编辑:3

在第3:3行输入要存储的输入

祝贺……错误编辑成功。

target.txt的内容: –

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2

3

4

6

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