Thread: while loop trouble

  1. #1
    Musicman - Canora
    Join Date
    Aug 2005

    while loop trouble

    Hey guys im trying to read in a file and list numbers to each line in the file but for some reason im getting a runtime logical error inside my while loop.

    #include <stdio.h>
    #include <stdlib.h>
    int main(int argc, char **argv)
        int line_no = 0;
        int input_char = 0;
        int nl = 1;
        FILE *fp;
        if(argc !=2) /* check for 2 arguments*/
          fprintf(stderr, "invalid usage :%s\n", argv[0]);
          return 1; /* stop processing if failes */
        if((fp = fopen(argv[1], "r")) == NULL) 
        /* opens file for reading and checks if it exists */
         fprintf(stderr, "invalid usage: %s\n", argv[0]);
         return 1; /* stop processing if fails*/
          while(input_char !=EOF)
              /* keep asking for input while not end of file*/
              if ( nl )
                 printf("\n%d ", line_no);
    	     putc(input_char, stdout);
    	     input_char = getc(fp);   
    	     nl = input_char == '\n';
        return EXIT_SUCCESS;

  2. #2
    Registered Luser cwr's Avatar
    Join Date
    Jul 2005
    Sydney, Australia
    You are starting off with nl equal to 1, then in the while loop, you are checking if nl is true (non-zero). Since it is, it simply prints line_no then increases line_no. nl is not set to zero, so the while loop goes back again, nl is still 1.. so this goes on forever.

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