Thread: Using strncmp to compare input with string

scanf() for strings will stop at the first whitespace character, so if you're typing "Patrick M" it actually only reads in "Patrick", then it prints the 2 Patrick matches, then on the next loop it reads in the leftover "M" and prints the Maxum match for that. Check out fgets() instead for input.

Originally Posted by itsme86

scanf() for strings will stop at the first whitespace character, so if you're typing "Patrick M" it actually only reads in "Patrick", then it prints the 2 Patrick matches, then on the next loop it reads in the leftover "M" and prints the Maxum match for that. Check out fgets() instead for input.

After a few hours I thought I figured out how this fgets() worked. But now when I push ENTER it writes all strings in my array. Why is that?

I realised that fgetc put \n in the end, so i found a way to remove it.

And is this how fgetc should be used? Or am I doing it wrong?

Code:

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

int main ()
{
    char stop[]={"STOP"};
    int i;
    char array[][80]={"Kalle","Peter","Maxum","Einsten",
        "Patrick Zen","Patrick Mark","Patricia Yrsa","Yrsan Dabom"};
    
    printf("Type a name:\n");
    char buffer[30];
    for(;;)
    {
        fgets(buffer,30, stdin);
        for ( i = 0; i < 30; i++ )
        {
            if ( buffer[i] == '\n' )
            {
                buffer[i] = '\0';
                break;
            }
        }
        if(strcmp(stop,buffer)==0)
        {
            break;
        }
        for(i=0;i<8;i++)
        {
            if(strncmp(array[i],buffer,strlen(buffer))==0)            
            {
                printf("%s\n",array[i]);
            }
        }


    
    
    }
}

Originally Posted by lovelace

Code:

if(strncmp(array[i],buffer,strlen(buffer))==0 && strlen(buffer) > 0)

If you did want to do it that way, you would be better off reversing those two checks.

Code:

if( strlen( buffer ) > 0 && strncmp( ... ) )

That way you would only strncmp if you had something to compare. It doesn't actually matter in a simple program like this, but it's good to get in the habit of thinking about the order that you check things, because you can short-circuit your comparisons and save your program time.


Quzah.

Originally Posted by itsme86

scanf() for strings will stop at the first whitespace character

More specifically, %s will stop at the first whitespace after it has read something that was not whitespace. Assuming you have not specified a width specifier as well.


Quzah.

Edit: itsme86 is also correct; so do his suggestion first.

This is wrong!

Code:

scanf("%s",&input);

This is right in my opinion

Code:

scanf("%s",input);

You need to turn on Compiler warnings and not ignore the warnings.

Code:

main.c|14|warning: format '%s' expects type 'char *', but argument 2 has type 'char (*)[80]'|
main.c|29|warning: control reaches end of non-void function|

Tim S.

And even better, you can just check to see if the first character in buffer is a \0 instead of counting each character in buffer and seeing if that count is greater than 0:

Code:

if(buffer[0] != '\0' && strncmp( ... ))