用C解析文件（行）

Question

I have a file that looks like this:

5
x=
6
y=

I want to initially skip the first line, parse the second line, then go back to the first line and strcat both strings. However, I can't seem to get that working.

For instance:

I have:

while(fgets(buffer,sizeof(buffer),file) != NULL) {

     fgets(buffer,100,file); //skip first line

     char * tempVar = malloc(sizeof(char)*10);

     strcpy(tempVar,buffer); //copy second line into tempVar

     rewind(file); //go back to first line? doesnt work

     //then strcat the two strings, so I get x=5

}

Note that my lines in my file are not always this simple, these are just example lines I'm trying to test out (Going back and fourth between lines, reading ahead etc).

Any ideas?

Answer 1

You can use int fseek ( FILE * stream, long int offset, int origin ); Where int origin can be

SEEK_SET    Beginning of file
SEEK_CUR    Current position of the file pointer
SEEK_END    End of file *

So if you know the offsets you can jump wherever you want.

edit:

FILE* file = fopen(fileName, "r"); 
char line[256];

fgets(line, sizeof(line), file); //skip first
fgets(line, sizeof(line), file);
printf("%s", line);  //  prints x=
fseek ( file , 0 , SEEK_SET );
fgets(line, sizeof(line), file); 
printf("%s", line);  // prints 5

Now if you want to loop that you need to save the offsets somewhere in order to jump back to them. You can do this by using strlen() on the buffer ( char line[256] ) in my example and add the offsets up.