Thread: strstr with integer

Say I have a user enter an integer from 0 - 255, and I want to search an arbitrary string for all occurrences of the ASCII value of that integer. I've thought about typecasting, itoa, and creating a function where I create a character array with all possible characters, but I keep thinking there has to be an easier way, like using %c in a printf statement.

The following code doesn't work, but hopefully it will show you my thinking:

Code:

do {
flag = 0;
printf( "Enter ASCII value( 0-255 ): " );
scanf( "%d", &value );
   if( value < 0 || value > 255 ) {
	printf( "Value must be 0 - 255, try again.\n" );
	flag = 1;
   }
}while( flag == 1);
			
printf( "Searching for character %c. . .\n\n\n", value );
			

/*  The following is a poor attempt, I know...but I am stuck at the
integer to character conversion.

int found[size];
for( i=0; i<size; i++ ) {
   if( strstr( file, (char)value ) != NULL ) {               // file is a file i've read into a string
	found[i] = 1;
}
   else{ found[i] = 0; }
}  */

What I need to do is if the user enters the integer 65, I need to search the string named file for the ascii character A. If they enter 77, I search for M, etc... So what I need to know is how to convert the input integer into it's ascii char equivalent.

I know a char is an 8-bit int, but I'm confused as to whether or not I need to create a new unsigned char( capable of storing 0-255) copying values bits to it.

Not at all.

k, here's strchr's prototype:

char *
strchr(const char *s, int c);

and that is all we need to know about strchr to use it. It's first parameter is a string to search for c in, and c, the second parameter, is the character (promoted to an integer anyway) that you want to find. The function will return a pointer to the first search result, or NULL for nothing. Coincidentally, that is all you have to care about to use it correctly, much of the standard library, and indeed, libraries in general are built to work like black boxes.

But I would pass a character constant to strchr() in your case, such as 'a', since the bitwise work you're doing seems pointless. The result of n | 0 for any n not 0 is n.

Originally Posted by k2712

What I need to do is if the user enters the integer 65, I need to search the string named file for the ascii character A. If they enter 77, I search for M, etc... So what I need to know is how to convert the input integer into it's ascii char equivalent.

You have to do nothing at all. Just call strchr(). This is exactly what it's for.