파일입출력 질문드립니다.

#include <stdio.h>
#include <stdlib.h>
 
main()
{
    FILE *fp, *fp1;
 
    int i;
    char cmd_buffer[300];
    char output_buffer[100];
 
    while(1) {
 
        if( (fp1 = fopen("/tmp/data.txt", "r+")) == NULL ) {
            fp = fopen("/tmp/data.txt", "w+");
            for(i=0; i<16; i++) {
                sprintf(cmd_buffer, "./CLI state %d", i);
 
                FILE *stream = popen(cmd_buffer, "r");
 
                if(stream != NULL) {
                    while(fgets(output_buffer, sizeof(output_buffer), stream) != NULL);
 
                    printf("%s\n", output_buffer);
                    fprintf(fp, "%s\n", output_buffer);
                }
            }
 
            fclose(fp);
            fclose(fp1);
        }
    }
}