即使删除“ file.txt”,程序仍会输入if
语句。
我要实现的是检查是否存在具有该名称的文件。如果是这样,则读取BookId
的最后一个值,并通过for
循环将其递增1:
FILE *myFile;
if (myFile==NULL) // if the file doesn't exists
{
myFile=fopen("file.txt","w"); // Fresh write
fprintf(myFile, "%s\t%s\t%s\t\n\n",Book_Id,Record_Date,Book_Name); // Column name (id, date, name)
//writing the values
for (x=0;x<NR_OF_BOOKS; x++)
{
fprintf(myFile, "%03d\t",BookId++);
fprintf(myFile, "%02d/%02d/%04d\t",dd[x],mm[x],yy[x]);
fprintf(myFile, "%s\n",Bookname[x]);
}
}
else // file exists
{
//reading
myFile=fopen("file.txt","r"); //open in read mode
fscanf(myFile,"%03d,",&BookId); // I want to read the last value of BookId
myFile=fopen("file.txt","a"); // I open in append mode to add BookId++
for (x=0;x<NR_OF_BOOKS; x++)
{
fprintf(myFile, "%03d\t",BookId++); // here continues to count the BookId
fprintf(myFile, "%02d/%02d/%04d\t",dd[x],mm[x],yy[x]); // date
fprintf(myFile, "%s\n",Bookname[x]);// book name
}
}
fclose(myFile); // closing the file
}
最佳答案
首先尝试打开文件进行读取。如果这不起作用(fopen
返回NULL
),则尝试打开进行写入。如果那也不起作用,您就要保释。
使用您的代码:
FILE *myFile = fopen("file.txt", "r+");
if (myFile != NULL)
{
// File exists and is now open for reading and writing...
}
else
{
myFile = fopen("file.txt", "w");
if (myFile == NULL)
{
// Report error and handle it appropriately
}
// The file didn't exist, now it is created so we can write to it
}
// All done with the file
fclose(myFile);
我建议您考虑将函数用于通用代码。
关于c - 检查文件是否存在于C中。如果是,则继续读取文件的最后一个值,并递增一个,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/49349319/