Difference between fgets and fread
Question
I have the following code below:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(void)
{
int lendata;
printf("Content-type:text/html\n\n");
printf("<html><body>");
lendata = atoi(getenv("CONTENT_LENGTH"));
char *buf = malloc(lendata+1);
fread(buf,lendata,1,stdin);
printf("%s\n<br>",buf);
printf("%d",lendata);
free(buf);
printf("</body></html>");
return 0;
}
When I use fgets , it truncates the data displayed. But when I use fread , it displays all the content. By the way, this is the CGI script for an html file upload using post method. Any help would be greatly appreciated.
2 answers
solution1
11 ACCPTED 2013-08-15 13:21:21
Both functions can be found well documented ( fread , fgets ) on the C++ website. Refer to them for the in depth and technical difference.
In short, fgets will read until the first new line, maximum bytes to read at once, or EOF , which ever is sent first whereas fread will read a specific number of words (where I define a word as a chunk of bytes, say groups of 4 bytes) and stop when that limit has been reached or 0 bytes have been read (typically means EOF or error).
If you wanted to use either function to read until EOF then it would look as follows:
char buffer[ buff_len ];
// ... zero-fill buffer here.
while ( fgets( buffer, buff_len, stdin ) != EOF ) {
// ... do something with buffer (will be NULL terminated).
}
while ( fread( buffer, sizeof( buffer[ 0 ] ), sizeof( buffer ) / sizeof( buffer[ 0 ] ), stdin ) != 0 ) {
// ... do something with buffer (not necessarily NULL terminated).
}
solution2
3 2013-08-15 13:17:57
fgets在遇到\\n时停止读取，而fread读取。
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