为什么fopen()返回空指针?
我试图在cont_br和cont_lan中的BRIDGE之后和LAN之后(分别为4和5)保存参数,但是fopen()不起作用......
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
void read_file(char file[]) {
char cont, *str, *ctrl_str;
int x=0, cont_br, cont_lan;
FILE *file_stream;
if (file_stream = fopen(file, "r")) {
while( !feof(file_stream) ) { //Check the file dimension
fgetc( file_stream );
x++;
}
x--;
str = (char*) malloc(sizeof(char) * x+1);
fseek(file_stream, 0, SEEK_SET); // Return at the beginning of the file
fread(str, x, 1, file_stream);
char delims[] = "#";
char *result = NULL;
result = strtok( str, delims);
while (result != NULL) {
if (result == "BRIDGE") { //Check the different "blocks" in the txt file
result = strtok(NULL, delims);
cont_br = atoi(result);
printf("Number of bridges: %d\n", cont_br);
}
result = strtok(NULL, delims);
if (result == "LAN") {
result = strtok(NULL, delims);
cont_lan = atoi(result);
printf("Number of Lan: %d\n", cont_lan);
}
break; //
}
}
printf("Error: can't open the file! errno: %d\n", errno);
fclose(file_stream);
}
int main() {
char file[] = "Config.txt";
read_file(file);
return 0;
}
这是Config.txt文件:
BRIDGE#4#
LAN#5#
192.168.0.1
192.168.1.1
192.168.2.1
192.168.3.1
192.168.4.1
#
LINK#
B1:3000,L1
B1:3001,L2
B1:3002,L3
B2:3000,L4
B2:3001,L5
B3:3000,L1
B4:3000,L3
B5:3000,L2
B2:3002,L3
答案 0 :(得分:2)
每当fopen失败,然后打印错误号(errno
)。
#include <error.h>
您应该包含标准errno.h并在代码中打印error
的值。然后查看错误代码并找到原因。
#include <stdio.h>
#include <errno.h>
int main()
{
errno = 0;
FILE *fb = fopen("/home/jeegar/filename", "r");
if (fb==NULL) {
printf("Error %d \n", errno);
printf("It's null");
}
else
printf("working");
}
这样,如果fopen失败,那么它将设置错误号。您可以在 fopen 中找到这些错误编号列表。