Closed. This question is off-topic。它当前不接受答案。
想改善这个问题吗？ Update the question，所以它是on-topic，用于堆栈溢出。
2年前关闭。
因此，我有一个名为bufptr的char *，其大小为512。在前两点中是我将要读取的文件的名称，之后的所有内容都是数据。
例如
我没有像那样初始化它，但这是一般的想法
之后，我使用strcpy将文件名存储到另一个文件中
例如
之后，我打开文件
我遇到的问题是fwrite部分。
我试着写
但是代替
我得到了
我将如何正确调用fwrite以便不会遇到此问题，或者是因为我没有跳过null？还是在null之前或之后有字符串？
编辑：
我添加了一个循环来检查bufptr并将其作为输出
这是我使用的循环
这是服务器代码
这是客户端文件
想改善这个问题吗？ Update the question，所以它是on-topic，用于堆栈溢出。
2年前关闭。
因此，我有一个名为bufptr的char *，其大小为512。在前两点中是我将要读取的文件的名称，之后的所有内容都是数据。
例如
char* bufptr = {'f', 'o', 'o', '.', 'c', '\0', ...}我没有像那样初始化它，但这是一般的想法
之后，我使用strcpy将文件名存储到另一个文件中
例如
auto int i = 0;
while(*bufptr != '\0')
{
fname[i++] = *bufptr;
bufptr++;
}
bufptr++;
之后，我打开文件
我遇到的问题是fwrite部分。
我试着写
fwrite(bufptr, 1, 512 - strlen(destString), fp)但是代替
// ============================================================================
// File: fcclient.c (Fall 2017)
// ============================================================================
我得到了
þ================================================我将如何正确调用fwrite以便不会遇到此问题，或者是因为我没有跳过null？还是在null之前或之后有字符串？
编辑：
我添加了一个循环来检查bufptr并将其作为输出
fcclient.c▒▒▒▒▒▒▒▒▒▒id▒.N=▒C▒h▒▒▒.8▒▒l▒ ▒ ▒▒▒`▒ ▒P▒▒▒H▒
▒`▒djd▒▒dd▒▒@▒
▒@▒(▒d▒p▒▒jd▒▒▒▒▒Бd▒=======================================================================
// File: fcclient.c (Fall 2017)
// ============================================================================
// This program is a file transfer client. The user at the keyboard is pread a total of 1 bytes
这是我使用的循环
auto int t = 0;
for(; t < 512; t+=)
if(*(bufptr + t) != '\0')
printf("%c", *(bufptr + t));
这是服务器代码
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
// prototypes
int CopyFile(int src_sock);
// defined constants
#define BUFLEN 512
#define SERVER_PORT 50004
#define TRUE 1
#define FALSE 0
// function prototypes
int CopyFile(int src_sock);
int main(void)
{
auto char buf[BUFLEN]; // local buffer
auto socklen_t client_addr_size; // used for call to accept
auto int client_socket; // used for call to accept
auto int server_socket; // used for call to socket
auto struct sockaddr_in client_address; // used for call to accept
auto struct sockaddr_in server_address; // used for call to bind
// greet the user
puts("Welcome to fcserver!");
puts("Waiting to recieve file from client...");
// create a socket for the server
server_socket = socket(AF_INET, SOCK_STREAM, 0);
// prepare the socket address structure for the server
memset(&server_address, 0, sizeof(server_address));
server_address.sin_family = AF_INET;
server_address.sin_addr.s_addr = htonl(INADDR_ANY);
server_address.sin_port = htons(SERVER_PORT);
// bind the server socket to an address, using the address structure
if(bind(server_socket, (struct sockaddr*) &server_address, sizeof(server_address)))
{
perror("server -- bind failed");
}
// put the server socket into a listening state
if(listen(server_socket, 5))
{
perror("server -- bind failed");
}
// let stdout know the server is waiting for a connection
puts("server waiting...");
// wait for an actual client connection (this will block)
client_addr_size = sizeof(server_address);
client_socket = accept(server_socket, (struct sockaddr*) &server_address, &client_addr_size);
CopyFile(client_socket);
// close the client and server sockets
close(client_socket);
close(server_socket);
return 0;
} // end of "main"
int CopyFile(int src_sock)
{
auto char buf[BUFLEN];
auto char *bufptr;
auto char fname[BUFLEN];
auto FILE* fptr;
auto int num_client_bytes;
auto unsigned long total_bytes = 0;
if(-1 == (num_client_bytes = recv(src_sock, bufptr, BUFLEN, 0)))
perror("server -- recv failed");
strcpy(fname, bufptr);;
auto int t = 0;
for(; t< num_client_bytes; t++)
{
if(*(bufptr + t) != '\0')
printf("%c", *(bufptr + t));
}
fptr = fopen(fname, "w");
auto int i = strlen(fname) +1;
bufptr += i;
total_bytes = fwrite(bufptr, sizeof(bufptr), 1, fptr);
printf("read a total of %lu bytes \n", total_bytes);
// loop and read the rest of the file from the client
do {
if(num_client_bytes == 0)
break;
printf("read a total of %d bytes \n", num_client_bytes);
total_bytes += fwrite(buf, 1, num_client_bytes, fptr);
} while (TRUE);
fclose(fptr);
printf("there were a total of %lu bytes written \n", total_bytes);
return TRUE;
} // end of "CopyFile"
这是客户端文件
// ============================================================================
// File: fcclient.c (Fall 2017)
// ============================================================================
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <sys/un.h>
#include <unistd.h>
#include <string.h>
#include <netinet/in.h>
#define BUFLEN 256
#define SERVER_PORT 50004
int main(void)
{
auto char buf[BUFLEN]; // general purpose buffer
auto int server_socket; // used for server socket
auto struct sockaddr_in server_address; // used for server address
auto char fname[BUFLEN]; // used for filename
auto char *bufptr; // used for heap block
auto FILE *fptr; // used for input file
auto int result; // used to check return values
auto long fileSize; // used to store file size
// greet the user
puts("Welcome to fcclient!");
// get the filename from stdin
printf("Please enter in the filename: ");
scanf("%s", fname);
// open the input file
fptr = fopen(fname, "r");
if(fptr == NULL)
{
printf("Sorry there was an error trying to locate the file. Please exit and try again \n");
return 0;
}
// get the size of the file
fseek(fptr, 0, SEEK_END);
fileSize = ftell(fptr);
fseek(fptr, 0, SEEK_SET);
// allocate a buffer to store the file in heap memory
bufptr = malloc(sizeof(char) * fileSize);
// create a socket to connect with the server
server_socket = socket(AF_INET, SOCK_STREAM, 0);
// setup a socket address structure to target the server
memset(&server_address, 0, sizeof(server_address));
server_address.sin_family = AF_INET;
server_address.sin_port = htons(SERVER_PORT);
server_address.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
printf("Currently connecting to server... \n");
// connect to the server
if(-1 == connect(server_socket, (struct sockaddr*) &server_address, sizeof(server_address)))
perror("client -- connect failed");
// send the filename to the server (include the NULL!)
if(-1 == send(server_socket, fname, BUFLEN, 0))
perror("client -- send failed");
// read the file into the allocated buffer
fseek(fptr, sizeof(bufptr),SEEK_SET);
if(0 == fread(bufptr, sizeof(bufptr), fileSize, fptr))
{
printf("There was an error sorry. \n");
return 0;
}
// send the data to the server
if(-1 == send(server_socket, bufptr, fileSize, 0))
perror("client -- send failed");
// close the input file and the sockets
fclose(fptr);
close(server_socket);
return 0;
} // end of "main"
最佳答案
bufptr不指向缓冲区的内容，因为bufptr += strlen(destString)，它指向内容旁边的位置。更新bufptr的值以指向您实际要编写的内容。
关于c - 如何正确使用fwrite？ ，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/47787406/
10-11 21:18