C language about input ouput with prinf function i exactly type yes but why can't i see output?

Question

#include<stdio.h>

int main(void)
{

    char name[40];      
    scanf("%s",name);

   if(name == "yes")    
   {
       printf("%s",name);
   }

   return 0
}

thank you so much can i ask why if(name=="yes") is not avalible? — RIPCpp, Nov 01 '18 at 14:57

score 1 · Accepted Answer · answered Nov 01 '18 at 14:44

1

You need to use strcmp for string comparison.

Replace

if(name == "yes")

With

if(strcmp(name,"yes") == 0)

strcmp returns

0 if both strings are identical (equal)
Negative value if the ASCII value of first unmatched character is less than second.
Positive value if the ASCII value of first unmatched character is greater than second.

answered Nov 01 '18 at 14:44

kiran Biradar

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thank you so much can i ask why if(name=="yes") is not avalible? – RIPCpp Nov 01 '18 at 14:57
1

@richbak: It has to do with how C treats array expressions - under most circumstances, an expression of array type "decays" to a pointer, so what you wind up comparing are the *addresses* of the strings, not their contents. There is a reason for this behavior, but it's more than will fit into a comment. – John Bode Nov 01 '18 at 14:58

score 0 · Answer 2 · answered Nov 01 '18 at 14:50

== isn't defined for string (or any other array) comparisons - you need to use the standard library function strcmp to compare strings:

if ( strcmp( name, "yes" ) == 0 )

or

if ( !strcmp( name, "yes") )

strcmp is a little non-intuitive in that it returns 0 if the string contents are equal, so the sense of the test will feel wrong. It will return a negative value if the first string is lexicographically less than the second, and a positive value if the first string is lexicographically greater than the second.

You'll need to #include <string.h> in order to use strcmp.

For comparing arrays that aren't strings, use memcmp.

C language about input ouput with prinf function i exactly type yes but why can't i see output?

2 Answers2