popen problem

Hi,

I have been learning about pipes in C recently. Here is an example of some code that works fine:

Code:

---

// some lines are omitted
        switch(fork()) {
                case -1:

                perror("Fork");
                exit(1);

                case 0:

                dup2(p[1], fileno(stdout));
                close(p[0]);
                close(p[1]);
                execl("/usr/bin/last", "last", 0);

                _exit(0);

                default:

                printf("parent\n");

                dup2(p[0], fileno(stdin));
                close(p[1]);
                close(p[0]);

                execl("/bin/sort", "sort", 0);
        }

---

Now this does exactly what it is supposed to do, last | sort , I'm trying to do all this with popen instead. Here is my attempt at that.

Code:

---

int main(void)
{
        FILE *fr, *fw;
        int i, j=0;

        char buffer[BUFSIZE];

        fr = popen("last", "r");
        fw = popen("sort", "w");

        while (fgets(buffer, sizeof(buffer), fr))
                fprintf(fw, "%s\n", buffer);

        pclose(fr);
        pclose(fw);
       
        return 0;
}

---

This almost works perfectly, except I get 10000 blank lines printing to stdout first. I know it's 10000 because I through in a counter at one point. After the blank lines it outputs semi-properly. every 10 lines or so a line that's not sorted properly appears. Thanks for any help/advice on this.

> fprintf(fw, "%s\n", buffer);
buffer already contains a newline from the fgets

Use fputs in place of fprintf

thanks, it actually works fine with fprintf after removing the \n
I will try with fputs as well