CODEWITHSUNDEEP
c++comparechars
Isawpalmetto
Isawpalmetto

Reputation: 795

Comparing chars in a character array with strcmp

I have read an xml file into a char [] and am trying to compare each element in that array with certain chars, such as "<" and ">". The char array "test" is just an array of one element and contains the character to be compared (i had to do it like this or the strcmp method would give me an error about converting char to cons char*). However, something is wrong and I can not figure it out. Here is what I am getting:
< is being compared to: < strcmp value: 44

Any idea what is happening?

char test[1];   
for (int i=0; i<amountRead; ++i)
{
    test[0] = str[i];
    if( strcmp(test, "<") == 0)
        cout<<"They are equal"<<endl;
    else
    {
        cout<<test[0]<< " is being compare to: "<<str[i]<<" strcmp value= "<<strcmp(test, "<") <<endl;
    }

}

Upvotes: 5

Views: 42632

Answers (3)

John Knoeller
John Knoeller

Reputation: 34148

you need to 0 terminate your test string. 

char test[2];   
for (int i=0; i<amountRead; ++i)
{
    test[0] = str[i];
    test[1] = '\0'; //you could do this before the loop instead.
    ...

But if you always intend to compare one character at a time, then the temp buffer isn't necessary at all. You could do this instead

for (int i=0; i<amountRead; ++i)
{
    if (str[i] == "<")
       cout<<"They are equal"<<endl;
    else
    {
        cout << str[i] << " is being compare to: <" << endl;
    }
}

Upvotes: 2

R Samuel Klatchko
R Samuel Klatchko

Reputation: 76541

strcmp wants both strings to be 0 terminated.

When you have non-0 terminated strings, use strncmp:

if( strncmp(test, "<", 1) == 0 )

It is up to you to make sure that both strings are at least N characters long (where N is the value of the 3rd parameter). strncmp is a good functions to have in your mental toolkit.

Upvotes: 1

Michael Burr
Michael Burr

Reputation: 340218

strcmp() expects both of its parameters to be null terminated strings, not simple characters. If you want to compare characters for equality, you don't need to call a function, just compare the characters:

if (test[0] == '<') ...

Upvotes: 4

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