检查行，然后在 txt 文件中更改其数据

Question

所以，我有这个：

order.txt

file.txt;10;21:21

file2.txt;3;20:00

file2.txt;30;22:20

file4.txt;3;10:00

我希望用户提供所需的行（1 到 3，取决于存在多少行），然后更改其内容。例如：

第 3 行

"文件名： file.txt"

"秒： 5"

"时间 HH:MM: 20:00"

输出/更改为 order.txt：

file.txt;10;21:21

file2.txt;3;20:20

file.txt;5;20:00

file4.txt;3;10:00

如您所见，第三行发生了变化。为此，我尝试了以下方法：

变量

FILE* orderFile;
FILE* contentFile;
char fileName[50];
char timeValue[10];
int seconds;
char orderNameFile[50];
char orderTimeFile[50];
int orderSecondsFile;
int count = 0;
int i = 0;
int line;
int position;

代码

/* This will show the content on it with the number of the line behind */
orderFile = fopen("order.txt","r+");
                
printf("\n");

while(fscanf(orderFile," %49[^;];%d; %49[^\n]",fileName,&seconds,timeValue) == 3)
{
    i++;
    printf("[%d] %s;%d;%s\n",i,fileName,seconds,timeValue);
}

printf("\n");

rewind(orderFile);
/* ******************************************************************* */

/* This will ask which line he wants to change */
do{

    printf("Choose the line you want to change\n");
    printf("[Line] ");
    scanf("%d",&line);
    printf("\n");

    if(line > i)
    {
         printf("That line does not exist\n\n");
    }

}while(line > i || line < 1);
/* ******************************************* */

/* This will ask for the file name, seconds and time in HH:MM */
printf("Insert the name of the file\n");
printf("[Name] ");
getchar();
scanf("%s",&orderNameFile);

printf("Insert the presentation time in seconds\n");
printf("[Time in seconds] ");
scanf("%d",&orderSecondsFile);

printf("Insert the hour it starts\n");
printf("[Time in HH:MM (Hour:Minutes)] ");
getchar();
scanf("%s%",&orderTimeFile);
/* ******************************************* */

/* This is what is supposed to edit the line I want but does not work */
while(fscanf(orderFile," %49[^;];%d; %49[^\n]",fileName,&seconds,timeValue) == 3)
{
    count++;

    if(count == line)
    {
        position = ftell(orderFile);
        fseek(orderFile, position, SEEK_SET);
        fprintf(orderFile,"%s;%d;%s",orderNameFile,orderSecondsFile,orderTimeFile);
        break;
    }
}
*/ ****************************************************************** */

fclose(orderFile);

我想要使用第一个示例的输出：

file.txt;10;21:21

file2.txt;3;20:20

file.txt;5;20:00

file4.txt;3;10:00

输出它使用第一个示例@EDITED：

file.txt;10;21:21

file2.txt;3;20:00

file2.txt;30;22:20file.txt;5;20:00

file4.txt;3;10:00

你有什么想法吗？

Answer 1

写入临时文件然后删除原始文件并将临时文件重命名为原始文件的名称通常效果更好

FILE *temp = fopen ( "temp", "w");
/* This is what is supposed to edit the line I want but does not work */
while(fscanf(orderFile," %49[^;];%d; %49[^\n]",fileName,&seconds,timeValue) == 3)
{
    count++;

    if(count == line)
    {
        fprintf(temp,"%s;%d;%s\n",orderNameFile,orderSecondsFile,orderTimeFile);
    }
    else 
    {
        fprintf(temp,"%s;%d;%s\n",filename,seconds,timeValue);
    }
}
fclose ( temp);
fclose ( orderFile);
remove ( "order.txt");// comment these two lines out until you are sure temp is correct
rename ( "temp", "order.txt");//that way you do not loose the original file

Answer 2

删除文件的内容是一项昂贵的操作，更好的处理方法是

1. 以写入模式打开一个新文件
2. 开始将之前文件的内容写入这个新文件。
3. 一旦到达应该被替换的行，请确保忽略读取行并使用 fprintf() 将新行写入新文件

IMO 这是更容易和正确的方法。使用下面的线程作为参考

Delete a Line from a file in C Language

Answer 3

您必须存储这些行，然后将它们重写到文件中，可能会有更优雅/高效的解决方案，但对于一个简单的情况，这应该没问题，这里是代码

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

int main()
{
    FILE* orderFile;
    char fileName[50];
    char timeValue[10];
    int seconds;
    char orderNameFile[50];
    char orderTimeFile[50];
    int orderSecondsFile;
    int count;
    int lineCount;
    int line;
    char lineContent[128];
    char fileLines[128][128];

    /* This will show the content on it with the number of the line behind */
    orderFile = fopen("order.txt", "r+");
    if (orderFile == NULL)
        return -1;
    lineCount = 0;

    while ((fgets(lineContent, sizeof(lineContent), orderFile) != NULL) && (lineCount < 128))
    {
        size_t length;

        length = strlen(lineContent);
        if (lineContent[length - 1] == '\n')
            lineContent[length - 1] = 0;
        if (sscanf(lineContent, " %49[^;];%d; %49[^\n]", fileName, &seconds, timeValue) == 3)
        {
            strcpy(fileLines[lineCount], lineContent);
            printf("[%d] %s;%d;%s\n", ++lineCount, fileName, seconds, timeValue);
        }
    }
    printf("\n");

    rewind(orderFile);

    /* This will ask which line he wants to change */
    do {

        printf("Choose the line you want to change\n");
        printf("[Line] > ");

        scanf("%d", &line);

        if ((line > lineCount) || (line < 1))
             printf("That line does not exist\n\n");
    } while ((line > lineCount) || (line < 1));

    /* This will ask for the file name, seconds and time in HH:MM */
    printf("Insert the name of the file\n");
    printf("[Name] ");

    scanf("%49s", orderNameFile);

    printf("Insert the presentation time in seconds\n");
    printf("[Time in seconds] ");

    scanf("%d", &orderSecondsFile);

    printf("Insert the hour it starts\n");
    printf("[Time in HH:MM (Hour:Minutes)] ");

    scanf("%49s", orderTimeFile);

    /* This is what is supposed to edit the line I want but does not work */
    count = 0;
    while (++count < lineCount + 1)
    {
        if (count == line)
            fprintf(orderFile, "%s;%d;%s\n", orderNameFile, orderSecondsFile, orderTimeFile);
        else
            fprintf(orderFile, "%s\n", fileLines[count - 1]);
    }
    fclose(orderFile);

    return 0;
}