convert ascii lower case to uppercase (c program)

[_jamie]

hey all...There's probably a few bugs. Program works fine on one line of text but won't run through spaces or multiple lines. This program won't convert a C program source file, just ouputs one line and ends when theres a space. Thanks! (very new to programming, about 9 months so far since February of this year), and the if & else if functions might have a few bugs.. thanks for support all! Thanks

#include <stdio.h>

int file_copy(char *oldname, char *newname);

int main( void )
{
    char source[80], destination[80];

    /* Get the source and destination names. */

    printf("\nEnter source file: ");
    gets(source);
    printf("\nEnter destination file: ");
    gets(destination);

    if(file_copy(source, destination) == 0)
        puts("Copy operation successful");
    else
        fprintf(stderr, "Error during copy operation");

    return (0);
}

int file_copy( char *oldname, char *newname )
{
    FILE *fold, *fnew;
    int c;

    /* Open the source file for reading in binary mode. */ 

    if ( ( fold = fopen( oldname, "rb" ) ) == NULL )
        return -1;
    
    /* Open the desintation file for writing in binary mode. */

    if ( ( fnew = fopen( newname, "wb" ) ) == NULL )
    {
        fclose ( fold );
        return -1;
    }

    while (1)
    {
        c = fgetc ( fold );
        if (!feof(fold))
        {
            // lower case to upper case
            
            if(c >= 'a' && c <= 'z')
            {
                c = 'A' + c - 'a';
            }    
            
            // upper case stays upper case
            
            else if (c >= 'A' && c <= 'Z')
            {
                c = c;
            }
            
            // digits 0 through 9 stays the same 

            else if (c >= 32 && c <= 127)
            {
                c = c;
            }

            else
            {
                break;
            }

            fputc( c, fnew );
        }
    }


    fclose ( fnew );
    fclose ( fold );

    return 0;
}

below: looked at ASCII chart and this isn't running through a long text file (spaces and new lines aren't following as they should)

            else if (c >= 32 && c <= 127)
            {
                c = c;
            }

[jimblumberg]

hey all...There's probably a few bugs.

No doubt. Probably the biggest bug is the use of the horribly dangerous gets() function, consider fgets() instead.

Next have you considered using toupper() or tolower() instead of trying to roll your own?

Be careful, ASCII is not the only type of character encoding and the alpha characters are not guaranteed to be consecutive. However if all you need to worry about is ASCII then do you realize that there is a definite offset between the capital and lower case letters (study the ASCII chart for more information).

For the last snippet, don't forget about the linefeed and carriage return character and several other whitespace characters that appear before the space character (decimal 32).

[laserlight]

gets is a huge bug: it is inherently vulnerable to buffer overflow.

Your controlled infinite loop has a structure that looks like it could really be an infinite loop:

while (1)
{
    c = fgetc ( fold );
    if (!feof(fold))
    {
        // ...
    }
}

Suppose feof(fold) returns true. Then you will loop forever. Of course, you might reason that no, before this can ever be the case you will in fact reach the break statement, but that's harder to see and arguably uncertain. It would be better to write:

while ((c = fgetc(fold)) != EOF)
{
    // ...
}

This statement has no net effect:

c = c;

so when you don't want c to change because it is already in the destination case or not a letter, you should simply structure your code to do nothing for these cases:

while ((c = fgetc(fold)) != EOF)
{
    // lower case to upper case
    if (c >= 'a' && c <= 'z')
    {
        c = c - 'a' + 'A';
    }

    fputc(c, fnew);
}

[_jamie]

Thank's for the help both of you.