Programming Forums > Application Development > C

Xenon · Nov 13th, 2005, 12:14 AM

Hi, Ive written the following function in the attempt to allow the user to be able to change the console colour whenever they want, but I dont know how to pass the two seperate HEX digits to the system, I tried using:

(Toggle Plain Text)

system("Color &colour");

But that didnt work, heres my function:

(Toggle Plain Text)

void colour()
{
    char colour[3];
    char inbuf[30];
    
printf("\nColour attributes are specified by TWO hex digits -- the first");
printf("\ncorresponds to the background; the second the foreground.  Each digit");
printf("\ncan be any of the following values:\n\n");

printf("    0 = Black       8 = Gray\n");
printf("    1 = Blue        9 = Light Blue\n");
printf("    2 = Green       A = Light Green\n");
printf("    3 = Aqua        B = Light Aqua\n");
printf("    4 = Red         C = Light Red\n");
printf("    5 = Purple      D = Light Purple\n");
printf("    6 = Yellow      E = Light Yellow\n");
printf("    7 = White       F = Bright White\n");

printf ("\nPlease enter the two Hex digits that correspond to the colours\n");
printf ("you would you like the backround and foreground to be:");
         if(gets(colour) == NULL) ;
		sscanf(inbuf,"%colour",&colour);

		system("Color &colour");
	
app_settings();	
		
}

Can anyone help?

andro · Nov 13th, 2005, 1:15 AM

Try something like this:

(Toggle Plain Text)

	char color[10] = "Color ";
	char value[2];

	cout << "Hex value: ";
	cin >> value;

	strcat_s(color, value);
	system(color);

DaWei · Nov 13th, 2005, 6:58 AM

Andro might have read your mind, but remember that you probably need to specify a platform/OS for things like this. Won't work on a TTY at all, for instance.

Xenon · Nov 13th, 2005, 7:48 AM

Im on Win XP, and Im using ansi C so Cout and Cin dont work (atleast I dont think they do Ive only been learning this for a short time)

With the following code, if I enter for example 'A0', the value stored in colour is "A0A0lolo", I cant work out why this is happening.

I tried using

(Toggle Plain Text)

strncat(colour,value, 2);

but then the value is just 'A0'.

(Toggle Plain Text)

void colour()
{
     
 char colour[10] = "Color ";
 char value[2];
 char inbuf[30];
    
printf("\nColour attributes are specified by TWO hex digits -- the first");
printf("\ncorresponds to the background; the second the foreground.  Each digit");
printf("\ncan be any of the following values:\n\n");

printf("    0 = Black       8 = Gray\n");
printf("    1 = Blue        9 = Light Blue\n");
printf("    2 = Green       A = Light Green\n");
printf("    3 = Aqua        B = Light Aqua\n");
printf("    4 = Red         C = Light Red\n");
printf("    5 = Purple      D = Light Purple\n");
printf("    6 = Yellow      E = Light Yellow\n");
printf("    7 = White       F = Bright White\n");

printf ("\nPlease enter the two Hex digits that correspond to the colours\n");
printf ("you would you like the backround and foreground to be:");
         if(gets(value) == NULL) ;
		sscanf(inbuf,"%value",&value);

	strcat(colour,value);
	printf("%s", colour);
	system(colour);

		
}

DaWei · Nov 13th, 2005, 9:42 AM

Cin and cout are C++ thangys. This is the C forum.

One presumes this is for practice, since there's a built-in command to do it. That means there are many ways. This particular method takes its arguments from the command line. It differs slightly in that it allows the arguments to be specified as a single-argument pair, or as two separate arguments. There is a modicum of validation.

If you wished to take keyboard input and deal with it as hex digits (rather than encoded alphanumeric characters), you might use something like 'scanf ("%x%[, ]%x", &dig1, &dig2);' This would be good practice. You must test the return from scanf, because you can't guarantee what your user will enter. If you received one assignment, you could validate for a packed pair; if you received two assignments, you could validate for individual digits. Anything else would constitute an error. As Larry Wall says, "TMTOWTDIR" (there's more than one way to do it right). Unfortunately, there's more than one way to do it wrong, too.

(Toggle Plain Text)

#include <stdio.h>
#include <string.h>

int ohDratMartha (char *badNews)
{
    fprintf (stderr, "%s\n", badNews);
    return 1;
}
int isColor (char hexdigit)
{
    int i;
    char *validDigits = "0123456789abcdef";
    hexdigit = tolower (hexdigit);
    for (i = 0; i < strlen (validDigits); i++)
        if (validDigits [i] == hexdigit) return 1;
    return 0;
}

int main (int argc, char *argv [])
{
    char color [9] = "color ";
    if (argc < 2) strcat (color, "0f"); // default
    else if (argc == 2)
    {
        // Packed pair
        if (!isColor (argv [1][0]) ||
            !isColor (argv [1][1]) ||
            (strlen (argv [1]) > 2))
            return ohDratMartha ("Invalid color specification");
        strcat (color, argv [1]);
    }
    else if (argc > 3) 
        return ohDratMartha ("What the hell are the extra arguments for?");
    else 
    {
        // Separate arguments
        if ((strlen (argv [1]) > 1) ||
            (strlen (argv [2]) > 1) ||
            !isColor (argv [1][0])  ||
            !isColor (argv [2][0]))
            return ohDratMartha ("Invalid color specification");
        strcat (color, argv [1]);
        strcat (color, argv [2]);
    }
    system (color);
    return 0;
}

This was only cursorily tested. Your mileage may vary. Your warranty expired day before yesterday.

Xenon · Nov 13th, 2005, 9:47 AM

Thankyou very much DaWei, thats great.

Nov 13th, 2005, 12:14 AM	#1
Xenon Programmer Join Date: Oct 2005 Location: UK Posts: 31 Rep Power: 0	Changing Console colour dynamically Hi, Ive written the following function in the attempt to allow the user to be able to change the console colour whenever they want, but I dont know how to pass the two seperate HEX digits to the system, I tried using: (Toggle Plain Text) system("Color &colour"); system("Color &colour"); But that didnt work, heres my function: (Toggle Plain Text) void colour() { char colour[3]; char inbuf[30]; printf("\nColour attributes are specified by TWO hex digits -- the first"); printf("\ncorresponds to the background; the second the foreground. Each digit"); printf("\ncan be any of the following values:\n\n"); printf(" 0 = Black 8 = Gray\n"); printf(" 1 = Blue 9 = Light Blue\n"); printf(" 2 = Green A = Light Green\n"); printf(" 3 = Aqua B = Light Aqua\n"); printf(" 4 = Red C = Light Red\n"); printf(" 5 = Purple D = Light Purple\n"); printf(" 6 = Yellow E = Light Yellow\n"); printf(" 7 = White F = Bright White\n"); printf ("\nPlease enter the two Hex digits that correspond to the colours\n"); printf ("you would you like the backround and foreground to be:"); if(gets(colour) == NULL) ; sscanf(inbuf,"%colour",&colour); system("Color &colour"); app_settings(); } void colour() { char colour[3]; char inbuf[30]; printf("\nColour attributes are specified by TWO hex digits -- the first"); printf("\ncorresponds to the background; the second the foreground. Each digit"); printf("\ncan be any of the following values:\n\n"); printf(" 0 = Black 8 = Gray\n"); printf(" 1 = Blue 9 = Light Blue\n"); printf(" 2 = Green A = Light Green\n"); printf(" 3 = Aqua B = Light Aqua\n"); printf(" 4 = Red C = Light Red\n"); printf(" 5 = Purple D = Light Purple\n"); printf(" 6 = Yellow E = Light Yellow\n"); printf(" 7 = White F = Bright White\n"); printf ("\nPlease enter the two Hex digits that correspond to the colours\n"); printf ("you would you like the backround and foreground to be:"); if(gets(colour) == NULL) ; sscanf(inbuf,"%colour",&colour); system("Color &colour"); app_settings(); } Can anyone help?

Nov 13th, 2005, 1:15 AM	#2
andro Professional Programmer Join Date: Oct 2005 Location: California Posts: 294 Rep Power: 3	Try something like this: (Toggle Plain Text) char color[10] = "Color "; char value[2]; cout << "Hex value: "; cin >> value; strcat_s(color, value); system(color); char color[10] = "Color "; char value[2]; cout << "Hex value: "; cin >> value; strcat_s(color, value); system(color);

Nov 13th, 2005, 6:58 AM	#3
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Andro might have read your mind, but remember that you probably need to specify a platform/OS for things like this. Won't work on a TTY at all, for instance. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Nov 13th, 2005, 7:48 AM	#4
Xenon Programmer Join Date: Oct 2005 Location: UK Posts: 31 Rep Power: 0	Im on Win XP, and Im using ansi C so Cout and Cin dont work (atleast I dont think they do Ive only been learning this for a short time) With the following code, if I enter for example 'A0', the value stored in colour is "A0A0lolo", I cant work out why this is happening. I tried using (Toggle Plain Text) strncat(colour,value, 2); strncat(colour,value, 2); but then the value is just 'A0'. (Toggle Plain Text) void colour() { char colour[10] = "Color "; char value[2]; char inbuf[30]; printf("\nColour attributes are specified by TWO hex digits -- the first"); printf("\ncorresponds to the background; the second the foreground. Each digit"); printf("\ncan be any of the following values:\n\n"); printf(" 0 = Black 8 = Gray\n"); printf(" 1 = Blue 9 = Light Blue\n"); printf(" 2 = Green A = Light Green\n"); printf(" 3 = Aqua B = Light Aqua\n"); printf(" 4 = Red C = Light Red\n"); printf(" 5 = Purple D = Light Purple\n"); printf(" 6 = Yellow E = Light Yellow\n"); printf(" 7 = White F = Bright White\n"); printf ("\nPlease enter the two Hex digits that correspond to the colours\n"); printf ("you would you like the backround and foreground to be:"); if(gets(value) == NULL) ; sscanf(inbuf,"%value",&value); strcat(colour,value); printf("%s", colour); system(colour); } void colour() { char colour[10] = "Color "; char value[2]; char inbuf[30]; printf("\nColour attributes are specified by TWO hex digits -- the first"); printf("\ncorresponds to the background; the second the foreground. Each digit"); printf("\ncan be any of the following values:\n\n"); printf(" 0 = Black 8 = Gray\n"); printf(" 1 = Blue 9 = Light Blue\n"); printf(" 2 = Green A = Light Green\n"); printf(" 3 = Aqua B = Light Aqua\n"); printf(" 4 = Red C = Light Red\n"); printf(" 5 = Purple D = Light Purple\n"); printf(" 6 = Yellow E = Light Yellow\n"); printf(" 7 = White F = Bright White\n"); printf ("\nPlease enter the two Hex digits that correspond to the colours\n"); printf ("you would you like the backround and foreground to be:"); if(gets(value) == NULL) ; sscanf(inbuf,"%value",&value); strcat(colour,value); printf("%s", colour); system(colour); }

Nov 13th, 2005, 9:42 AM	#5
DaWei Resident Grouch Join Date: Jun 2005 Posts: 6,453 Rep Power: 10	Cin and cout are C++ thangys. This is the C forum. One presumes this is for practice, since there's a built-in command to do it. That means there are many ways. This particular method takes its arguments from the command line. It differs slightly in that it allows the arguments to be specified as a single-argument pair, or as two separate arguments. There is a modicum of validation. If you wished to take keyboard input and deal with it as hex digits (rather than encoded alphanumeric characters), you might use something like 'scanf ("%x%[, ]%x", &dig1, &dig2);' This would be good practice. You must test the return from scanf, because you can't guarantee what your user will enter. If you received one assignment, you could validate for a packed pair; if you received two assignments, you could validate for individual digits. Anything else would constitute an error. As Larry Wall says, "TMTOWTDIR" (there's more than one way to do it right). Unfortunately, there's more than one way to do it wrong, too. (Toggle Plain Text) #include <stdio.h> #include <string.h> int ohDratMartha (char badNews) { fprintf (stderr, "%s\n", badNews); return 1; } int isColor (char hexdigit) { int i; char validDigits = "0123456789abcdef"; hexdigit = tolower (hexdigit); for (i = 0; i < strlen (validDigits); i++) if (validDigits [i] == hexdigit) return 1; return 0; } int main (int argc, char argv []) { char color [9] = "color "; if (argc < 2) strcat (color, "0f"); // default else if (argc == 2) { // Packed pair if (!isColor (argv [1][0]) \|\| !isColor (argv [1][1]) \|\| (strlen (argv [1]) > 2)) return ohDratMartha ("Invalid color specification"); strcat (color, argv [1]); } else if (argc > 3) return ohDratMartha ("What the hell are the extra arguments for?"); else { // Separate arguments if ((strlen (argv [1]) > 1) \|\| (strlen (argv [2]) > 1) \|\| !isColor (argv [1][0]) \|\| !isColor (argv [2][0])) return ohDratMartha ("Invalid color specification"); strcat (color, argv [1]); strcat (color, argv [2]); } system (color); return 0; } #include <stdio.h> #include <string.h> int ohDratMartha (char badNews) { fprintf (stderr, "%s\n", badNews); return 1; } int isColor (char hexdigit) { int i; char validDigits = "0123456789abcdef"; hexdigit = tolower (hexdigit); for (i = 0; i < strlen (validDigits); i++) if (validDigits [i] == hexdigit) return 1; return 0; } int main (int argc, char argv []) { char color [9] = "color "; if (argc < 2) strcat (color, "0f"); // default else if (argc == 2) { // Packed pair if (!isColor (argv [1][0]) \|\| !isColor (argv [1][1]) \|\| (strlen (argv [1]) > 2)) return ohDratMartha ("Invalid color specification"); strcat (color, argv [1]); } else if (argc > 3) return ohDratMartha ("What the hell are the extra arguments for?"); else { // Separate arguments if ((strlen (argv [1]) > 1) \|\| (strlen (argv [2]) > 1) \|\| !isColor (argv [1][0]) \|\| !isColor (argv [2][0])) return ohDratMartha ("Invalid color specification"); strcat (color, argv [1]); strcat (color, argv [2]); } system (color); return 0; } This was only cursorily tested. Your mileage may vary. Your warranty expired day before yesterday. __________________ Abstraction doesn't make it impossible to write bad code; it makes it possible to write superior code. Contributor's Corner: Grumpy on C++ Exceptions DaWei on Pointers

Nov 13th, 2005, 9:47 AM	#6
Xenon Programmer Join Date: Oct 2005 Location: UK Posts: 31 Rep Power: 0	Thankyou very much DaWei, thats great.

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Programming Forums > Application Development > C

Changing Console colour dynamically