在这个程序中,我尝试编写一个文件,显示用户输入的未知数量的记录。每条记录都有以下字段:名字,姓氏,地址,城市,州,邮政编码和电话号码。我认为最好的方法是使用上面的字段定义一个struct Record,然后声明一个包含与用户输入的记录一样多的记录数组。为了实现这一点,我将使用循环来获取每个记录的每个字段的输入,然后如果用户想要继续在Record数组中动态分配额外的空间并继续直到用户输入no。程序编译并创建文件,但写的字符非常奇怪。是什么导致这种情况发生?
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
struct Record
{
char fname[51];
char lname[51];
char address[51];
char city[51];
char state[51];
int zipcode;
int phoneNumber;
};
int main()
{
FILE *fileWriter;
const char filename[] = "data.txt";
char answer = 'y';
int size = 1;
int i = 0;
struct Record *records = NULL;
struct Record *records_temp;
while(answer == 'y' || answer == 'Y')
{
struct Record *records_temp = realloc(records,(size)*sizeof(*records));
if(records_temp == NULL)
{
free(records);
}
records = records_temp;
printf("First Name: \n");
scanf("%s", records[i].fname);
printf("Last Name: \n");
scanf("%s", records[i].lname);
printf("Address: \n");
scanf(" %[^\n]", records[i].address);
printf("City: \n");
scanf("%s", records[i].city);
printf("State: \n");
scanf("%s", records[i].state);
printf("Zipcode: \n");
scanf("%d", &records[i].zipcode);
printf("Phone Number: \n");
scanf("%d", &records[i].phoneNumber);
//stores all record info
printf("Are there anymore records? [y/n] ");
answer = getchar();
if(answer == 'y' || answer == 'Y')
{
size++;
records[i++];
printf("\n");
}
//open file
fileWriter = fopen(filename,"wb");
if(fileWriter != NULL)
{
if(fwrite(records,sizeof(*records),size,fileWriter) != 1)
{
fprintf(stderr, "Failed to write to %s\n", filename);
exit(1);
}
fclose(fileWriter);
}
else
{
printf("Error opening file.");
}
}
}
已编辑版本 我修改了代码并修复了许多正在发生的错误,但现在我在scanf上遇到了访问冲突(“%c”,回答)
#include <stdio.h>
#include <stdlib.h>
#include <conio.h>
struct Record
{
char fname[51];
char lname[51];
char address[51];
char city[51];
char state[51];
char zipcode[51];
char phoneNumber[51];
};
int main()
{
FILE *fileWriter;
const char filename[] = "data.txt";
char answer = 'y';
char a = 'n';
int size = 1;
int i = 0;
struct Record *records;
struct Record *records_temp = NULL;
while(answer == 'y' || answer == 'Y')
{
struct Record *records_temp = calloc((size),sizeof(*records));
records = records_temp;
printf("First Name: \n");
scanf("%s", records[size-1].fname);
printf("Last Name: \n");
scanf("%s", records[size-1].lname);
printf("Address: \n");
scanf(" %[^\n]", records[size-1].address);
printf("City: \n");
scanf("%s", records[size-1].city);
printf("State: \n");
scanf("%s", records[size-1].state);
printf("Zipcode: \n");
scanf("%s", records[size-1].zipcode);
printf("Phone Number: \n");
scanf("%s", records[size-1].phoneNumber);
//stores all record info
printf("Are there anymore records? [y/n] ");
scanf(" %c", answer);
if(answer == 'y' || answer == 'Y')
{
size++;
printf("\n");
}
}
//open file
fileWriter = fopen(filename,"wb");
if(fileWriter != NULL)
{
for(;i< size; i++)
{
fprintf(fileWriter,"%s\n",records[i].fname);
fprintf(fileWriter,"%s\n",records[i].lname);
fprintf(fileWriter,"%s\n",records[i].address);
fprintf(fileWriter,"%s\n",records[i].city);
fprintf(fileWriter,"%s\n",records[i].state);
fprintf(fileWriter,"%d\n",records[i].zipcode);
fprintf(fileWriter,"%d\n",records[i].phoneNumber);
}
fclose(fileWriter);
}
else
{
printf("Error opening file.");
}
}
答案 0 :(得分:3)
如果分配内存,则不会清除此内存。
char *data = (char*)malloc(100);
这会为100个字符分配内存。但是内存可以包含随机数据。如果从这个地址写入,最终可能会将随机数据写入文件。
清除内存以确保没有随机数据。
memset(data, 0, 100);
或struct
:
struct Demo {
int a;
int b;
};
Demo *demo = (Demo*)malloc(sizeof(Demo));
memset(demo, 0, sizeof(Demo));
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
struct Record
{
char fname[51];
char lname[51];
char address[51];
char city[51];
char state[51];
int zipcode;
int phoneNumber;
};
int main()
{
char answer = 'y';
int size = 0;
Record *records = NULL;
do {
++size;
// resize records array.
if (records == NULL) {
records = (Record*)malloc(sizeof(Record)*size);
} else {
records = (Record*)realloc(records, sizeof(Record)*size);
}
// Get a pointer to the current record.
Record *currentRecord = &records[size-1];
// Clear the record
memset(currentRecord, 0, sizeof(Record));
// Ask for all data.
printf("First Name: \n");
scanf("%s", currentRecord->fname);
printf("Last Name: \n");
scanf("%s", currentRecord->lname);
printf("Address: \n");
scanf(" %[^\n]", currentRecord->address);
printf("City: \n");
scanf("%s", currentRecord->city);
printf("State: \n");
scanf("%s", currentRecord->state);
printf("Zipcode: \n");
scanf("%d", &(currentRecord->zipcode));
printf("Phone Number: \n");
scanf("%d", &(currentRecord->phoneNumber));
// Ask for more.
printf("Are there anymore records? [y/n] ");
answer = getchar();
printf("\n");
} while (answer == 'y'||answer == 'Y');
// Write all records
const char filename[] = "data.txt";
FILE *fileWriter = fopen(filename, "wb");
if (fileWriter != NULL) {
if (fwrite(records, sizeof(Record), size, fileWriter) != size) {
fprintf(stderr, "Failed to write to %s\n", filename);
exit(1);
}
fclose(fileWriter);
} else {
printf("Error opening file.");
}
}
答案 1 :(得分:1)
fwrite(records,sizeof(*records),size,fileWriter)
有几个问题:
struct Record
包含5个以空字符结尾的字符串,因此您的文件将包含5个空字符,用于分隔这些字符串,您可能需要使用换行符。
struct Record
包含2个整数,这些整数作为二进制数据写入文件中,并且可以肯定符合文件中出现的奇怪字符&#34;。
您可以根据其特定类型编写每个字段来修复它:
fprintf(fileWriter,"%s\n",records->fname);
fprintf(fileWriter,"%s\n",records->lname);
fprintf(fileWriter,"%s\n",records->address);
fprintf(fileWriter,"%s\n",records->city);
fprintf(fileWriter,"%s\n",records->state);
fprintf(fileWriter,"%d\n",records->zipcode);
fprintf(fileWriter,"%d\n",records->phoneNumber);
答案 2 :(得分:1)
回答OP的评论问题,询问为什么程序会自动退出,我建议(通过示例)。请注意' '
之前的%c
空格,它会清除任何前面的空格。
#include<stdio.h>
int main(void) {
int phone;
char answer;
scanf("%d", &phone); // leaves newline in buffer
//answer = getchar(); // reads the newline still in buffer
scanf(" %c", &answer); // skips preceding white-space
return 0;
}