我正在使用Linux中的GET函数编写一个程序来模拟一个非常基本的Internet Explorer。我似乎唯一的问题是，我不确定如何从返回值中提取内容长度的值。现在我有硬编码的数字，但它们只适用于我的文件大小，而不是更大或更小的数字。如果我能设法解析内容长度，我可以解决这个问题。如果有人能让我走上解决问题的正确道路，我将非常感激。
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
/* VSIE client program uses TCP protocol to connect to the remote http server.
The program will take 2 input arguments:
1) command option, get (receive) or head (send)
2) http URL address
*/
#define MAX 80
#define MAX2 1024
#define http "HTTP/1.1"
#define TRUE 1
#define FALSE 0
#define HEADERSTOP "\n\n"
main(int argc, char *argv[])
{
unsigned char *e;
char command[MAX];
char server[MAX];
char path[MAX];
char filename[MAX]= "";
char httpString[MAX];
int i, x, f, n, length = 0;
int numBytes = 0;
int getData = TRUE;
int getFlag = FALSE;
int flag = FALSE;
int headFlag = FALSE;
FILE *in;
int sk;
unsigned char buf[MAX2];
struct sockaddr_in remote;
struct hostent *hp;
struct servent *sp;
short port = 0;
// parse input arguments
sscanf(argv[2],"%[^'/']%s",server,path);
if (strcmp(argv[1],"-get") == 0)
{
sprintf(command, "GET");
getFlag = TRUE;
}
else if (strcmp(argv[1],"-head") == 0)
{
sprintf(command, "HEAD");
}
//build http 1.1 GET or HEAD message
sprintf(httpString,"%s %s %s\nHost: %s\n\n", command, path,http,server);
printf("command = %s, server = %s, path = %s\n", command, server, path);
printf("httpString = %s\n",httpString);
//parse filename from path
length = strlen(path);
x=0;
f=0;
for(i = 0; i < length; i++)
{
//printf("path[%d] = %c \n",i,path[i]);
if ((flag == TRUE) & (f == 2))
{
filename[x] = path[i];
x++;
}
if (path[i] == '/')
{
flag = TRUE;
f++;
}
}
printf("filename = %s\n", filename);
//if command = get, open filename
//if(command == "-get")
if (getFlag == TRUE)
{
if((in = fopen (filename,"w")) == NULL)
{
//printf("FAILURE: opening input file %s\n",filename);
perror("FAILURE: opening input file");
exit(1);
}
printf("file opened successfully\n");
}
//get internet address of host & port number of http service
hp = gethostbyname(server);
if (hp == NULL)
{
printf("Can't find host name. %s\n", server);
exit (1);
}
//copy the h_addr (source) to s_add (destination) for n bytes specified by length
bcopy(hp->h_addr,&remote.sin_addr.s_addr,hp->h_length);
/* get the port number */
sp = getservbyname("http", "tcp");
if (sp == NULL)
{
printf("can't find port # %d\n",sp->s_port);
exit (1);
}
port = sp->s_port;
remote.sin_port = sp->s_port;
printf("port = %d, port = %d \n", port, remote.sin_port);
//create socket for http server - socket type: Sock_Stream, protocol: TCP
sk = socket(AF_INET,SOCK_STREAM,0);
if (sk < 0)
{
perror("error opening socket");
exit(1);
}
remote.sin_family = AF_INET;
//initiate connection to the server address w/ TCP socket
if (connect(sk, (struct sockaddr *) &remote, sizeof(remote)) < 0)
{
printf("connect fails!\n");
exit(1);
}
printf("connection successful\n");
//send http message
printf("send message:%s\n", httpString);
//send(sk,httpString,strlen(httpString)+1,0);
if(send(sk,httpString,sizeof(httpString),0) < 0)
{
printf("send() failed");
//exit(1);
}
n = 1;
//Loop until all data received
while(getData == TRUE)
{
//wait for and print the return message
numBytes = recv(sk,buf,sizeof(buf),0);
if (numBytes < 0)
{
perror("error reading from socket");
break;
}
else if (numBytes < MAX2)
{
getData = FALSE;
printf("***end while loop****\n");
}
if (headFlag == FALSE){
e = memchr(buf, '\n', sizeof(buf));
while (*(e+1) != '\r'){
e = memchr(e+1, '\n', sizeof(buf));
}
headFlag = TRUE;
}
printf("\n****number of bytes received %d****\n",numBytes);
//saved the retrieved content into the file (input argument)
if (getFlag == TRUE)
{
//printf("write output\n");
printf("%.*s\n", (numBytes-763), buf);
if(e != NULL){
fwrite(e, numBytes, 1, in);
e = NULL;
}else{
fwrite(buf, numBytes, 1, in);
}
}
n++;
} // end while()
//close socket & file
close(sk);
if(fclose(in) !=0)
{
perror("FAILURE: Closing input file");
exit(1);
}
return 0;
} //end main()
返回的信息是：
****number of bytes received 1024****
HTTP/1.1 200 OK
Date: Tue, 08 Apr 2014 17:37:10 GMT
Server: Apache/2.2.22 (Ubuntu)
Last-Modified: Tue, 18 Feb 2014 19:41:06 GMT
ETag: "1724117-9fb-4f2b373fef880"
Accept-Ranges: bytes
Content-Length: 2555
Vary: Accept-Encoding
Content-Type: text/html
答案 0 :(得分：2)
以下是一些代码，向您展示了一种方法。对你来说重要的是
strtok - split the string into lines
strstr - find a string that contains the words you are looking for
sscanf - scan the line for the value of the integer
其他所有东西都是为了让这个例子有效。
#include <stdio.h>
#include <string.h>
int main(void) {
char httpString[]="HTTP/1.1 200 OK\n"\
"Date: Tue, 08 Apr 2014 17:37:10 GMT\n"\
"Server: Apache/2.2.22 (Ubuntu)\n"\
"Last-Modified: Tue, 18 Feb 2014 19:41:06 GMT\n"\
"ETag: \"1724117-9fb-4f2b373fef880\"\n"\
"Accept-Ranges: bytes\n"\
"Content-Length: 2555\n"\
"Vary: Accept-Encoding\n"\
"Content-Type: text/html\n";
printf("string is %s\n", httpString);
char *line;
line = strtok(httpString, "\n");
while(line != NULL) {
if (strstr(line, "Content-Length:")!= NULL) {
int theNumber;
sscanf(line, "Content-Length: %d", &theNumber);
printf("The number is %d\n", theNumber);
}
line = strtok(NULL, "\n");
}
return 0;
}
输出：
string is HTTP/1.1 200 OK
Date: Tue, 08 Apr 2014 17:37:10 GMT
Server: Apache/2.2.22 (Ubuntu)
Last-Modified: Tue, 18 Feb 2014 19:41:06 GMT
ETag: "1724117-9fb-4f2b373fef880"
Accept-Ranges: bytes
Content-Length: 2555
Vary: Accept-Encoding
Content-Type: text/html
The number is 2555
或者 - 正如@enhzflep在评论中所提到的，如果你在原文中查找字符串Content-length:的索引，那么你可以使用在此之后开始的字符串做sscanf点：
char searchString[] = "Content-length:";
int offset, number;
offset = strstr(httpString, searchString);
sscanf(offset + strlen(searchString), "%d", &number);