manipulating files in place

This is a discussion on manipulating files in place within the C Programming forums, part of the General Programming Boards category; I'm trying to understand file streams and how they work and I'm still a little frustrated as to why this ...

  1. #1
    Registered User caroundw5h's Avatar
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    Oct 2003
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    manipulating files in place

    I'm trying to understand file streams and how they work and I'm still a little frustrated as to why this code wouldn't work - without calling fseek,
    Code:
    /*manipulating files in place */
    #include <stdio.h>
    #include <stdlib.h>
    #include <ctype.h>
    int main(int argc, char *argv[]){
        int ch,lower;
        FILE *file;
    
       
        
        if ( (file = fopen(argv[1], "r+") ) == NULL){
        	puts("Unable to open file");
        	getchar();
        	return 1;
         }   
      
        	
       	while( ( ch = fgetc(file) ) != EOF){
       	    if( (isupper(ch) ) )
       	      tolower(ch); 
       	      
        }    
           
        if ( fclose(file) !=0)
           puts("Unable to close file");
           
         getchar();
         return 0;
     }
    I got this
    If the file is opened in the update mode (+), then output cannot be directly followed by input and input cannot be directly followed by output without an intervening fseek, fsetpos, rewind, or fflush.
    but why?
    Last edited by caroundw5h; 09-20-2004 at 05:45 PM.
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  2. #2
    Guest Sebastiani's Avatar
    Join Date
    Aug 2001
    Location
    Waterloo, Texas
    Posts
    5,643
    read this post.
    Code:
    if( numeric_limits< byte >::digits != bits_per_byte )
        error( "program requires bits_per_byte-bit bytes" );
    24bbs.cpp

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