如何读取从文件中读取的特定行

Question

I have managed to read all the lines in my file to a char array but when I want to read a specific line ie line 254 as in the example below, I always get the data in the last line in my file. Any idea what's the problem. Thank you. Here is sample of the code:

 while (fgets(line,2000,fp)!=NULL
{
 readData [n] = line;
 n++;
}
printf ("print line after %s\n",readData [254]);

Answer 1

You're copying the pointer every time. So at the end every entry of the readData array will point to the same memory. Try to copy the data instead:

readData[n] = strdup(line);

And remember to free when done. If you don't have strdup or don't want to use it:

readData[n] = malloc(strlen(line) + 1);
strcpy(readData[n], line);

Answer 2

I'm guessing "readData" is an array of char*s, so when you say readData[n] = line you are always setting the array to the same "buffer" of data.

You need something a bit more like

char buffer[numLines][colsPerLine];
char line[colsPerLine];
while (fgets(line,2000,fp)!=NULL
{
   strcpy(buffer[n], line); // copy contents of line into the buffer
   n++;
}
printf ("print line after %s\n",buffer[254]);

Answer 3

You can use seek pointer to move cursor to line no . And then apply reading line . Hope it will work.