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问题描述
我有以下结构，我将其写入文件。
这是我的代码，用于编写，显示和删除文件中的记录。
当我写下记录并显示它工作正常但当我要求删除记录并再次打印它ID更改。
这是输出
i have the following structure and i am writing it to file.
Here are my code to write,display and delete the record from the file.
When i write the record and display it work fine but when i asked to delete the record and again print it id changes.
Here is the output
Enter the choice
1- Insert a new record into file
2- Update the record
3- Display the records
4- Delete the record
5- Close the connection with the server
1
Enter the id of the record
1
Enter name correspond to that id
ashishi
Client-write() is OK
String successfully sent!
Waiting the 10.0.2.15 to echo back...
Client-read() is OK
Echoed data from the following server: CREATED_RECORD
count incremented
Enter the choice
1- Insert a new record into file
2- Update the record
3- Display the records
4- Delete the record
5- Close the connection with the server
1
Enter the id of the record
2
Enter name correspond to that id
tarun
Client-write() is OK
String successfully sent!
Waiting the 10.0.2.15 to echo back...
Client-read() is OK
Echoed data from the following server: CREATED_RECORD
count incremented
Enter the choice
1- Insert a new record into file
2- Update the record
3- Display the records
4- Delete the record
5- Close the connection with the server
3
IN DISPLAY
value of count is 2
Client-write() is OK
String successfully sent!
value of count is 2
id is = 1 name is = ashishi
value of ii is 2
value of count is 2
id is = 2 name is = tarun
display loop ended
Enter the choice
1- Insert a new record into file
2- Update the record
3- Display the records
4- Delete the record
5- Close the connection with the server
4
Enter id to be deleted
1
enter to be deleted is 1
sending
sent
Client-write() is OK
String successfully sent!
Waiting the 10.0.2.15 to echo back...
Message from server is DELETED RECORD
Enter the choice
1- Insert a new record into file
2- Update the record
3- Display the records
4- Delete the record
5- Close the connection with the server
3
IN DISPLAY
value of count is 1
Client-write() is OK
String successfully sent!
value of count is 1
id is = 1 name is = tarun// why the id changes problem
display loop ended
Enter the choice
1- Insert a new record into file
2- Update the record
3- Display the records
4- Delete the record
5- Close the connection with the server
这里代码：
And here the code:
struct emprec
{
int empid;
int operation;
char name[20];
};
if (temp2.operation==1)//write record
{
count++;
fwrite(&temp2.empid,sizeof(temp2.empid),1,fd);
fwrite(&temp2.name,20,1,fd);
fclose(fd);
}
if (temp2.operation==4)//delete record
{
printf("In case 4 THAT IS DELETE \n");
int found =0,i=1;
fd = fopen(file_path,"r+");
if(fd==NULL)
{
printf("File cannot be opened\n");
memset(sbuf,0,sizeof(sbuf));
strcpy(sbuf,FILE_ERR);
printf("sbuf is %s\n",sbuf);
rc = write(sd2, sbuf, sizeof(sbuf));
return 1;
}
fd1 = fopen(file_path1,"a+");
if(fd1==NULL)
{
printf("File cannot be opened\n");
memset(sbuf,0,sizeof(sbuf));
strcpy(sbuf,FILE_ERR);
printf("sbuf is %s\n",sbuf);
rc = write(sd2, sbuf, sizeof(sbuf));
perror("fopen");
return 1;
}
printf("name to search is %s\n",temp2.name);
printf("id to delete is %d\n",temp2.empid);
emp temp7,temp10;
memcpy(&temp10,buffer,sizeof(temp10));
printf("temp 10 id to delete is %d\n",temp10.empid);
while(i<=count){
fread(&temp7.empid,sizeof(temp7.empid),1,fd);
fread(&temp7.name,sizeof(temp7.name),1,fd);
if(temp2.empid==temp7.empid){
printf("A requested by name found and deleted\n");
found = 1;
//fread(&temp7.empid,sizeof(temp7.empid),1,fd);
//fread(&temp7.name,sizeof(temp7.name),1,fd);
count--;
}else{
fwrite(&temp7,sizeof(temp7),2,fd1);
//fwrite(&temp7.empid,sizeof(temp7.empid),1,fd);
//fwrite(&temp7.name,20,1,fd);
//printf("NEW record in new file we are writing\n");
//printf("EMP id written is %d\n",temp7.empid);
//printf("EMP name written is %s\n",temp7.name);
}
if(!found)
{
printf("cannot found the record\n");
}
i++;
}
fclose(fd);
fclose(fd1);
remove(file_path);
rename(file_path1,file_path);
}
if (temp2.operation==3)//display
{
printf("In display\n");
emp temp6;
int i =1;
fd = fopen(file_path,"r+");
if(fd==NULL)
{
printf("File cannot be opened\n");
perror ("fopen");
return 1;
}
while(i<=count)
{
fread(&temp6.empid,sizeof(temp6.empid),1,fd);
fread(&temp6.name,sizeof(temp6.name),1,fd);
printf("\nid is = %d name is = %s\n",temp6.empid,temp6.name);
memset(sdata,0,sizeof(temp6));
memcpy(sdata,&temp6,sizeof(temp6));
printf("temp2.empname is %s\n",temp2.name);
rc = write(sd2, sdata, sizeof(temp6));//add a check here
sleep(1);
i++;
}
fclose(fd);
推荐答案
struct emprec
{
int empid;
int operation;
char name[20];
};
if (temp2.operation==1) //write record
{
count++;
fwrite(&temp2.empid,sizeof(temp2.empid),1,fd);
fwrite(&temp2.name,20,1,fd);
fclose(fd);
}
定义记录结构并在整个结构上执行I / O，这样更快，更不容易出错：
Define a record structure and perform I/O on the whole structure, that is faster and less error prone:
struct Record
{
int empid;
char name[20];
};
struct emprec
{
int operation;
struct Record record;
};
if (temp2.operation==1) //write record
{
count++;
fwrite(&temp2.record,sizeof(struct Record),1,fd);
fclose(fd);
}
通过这种方式你可以避免在删除程序中犯的错误：
In this way you would have avoided the error you made in the deleting routine:
...
while(i<=count)
{
fread(&temp7.empid,sizeof(temp7.empid),1,fd); //here correctly reads the two
fread(&temp7.name,sizeof(temp7.name),1,fd); //fields
if(temp2.empid==temp7.empid)
{
printf("A requested by name found and deleted\n");
found = 1;
count--;
}
else
{
fwrite(&temp7,sizeof(temp7),2,fd1); //But here you write the whole struct and 2 times its size!
}
...
可能是：
Could have been:
...
while(i<=count)
{
fread(&temp7.record,sizeof(struct Record),1,fd);
if(temp2.record.empid==temp7.record.empid)
{
printf("A requested by name found and deleted\n");
found = 1;
count--;
}
else
{
fwrite(&temp7.record,sizeof(struct Record),1,fd1);
}
...
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