Simple check for character in char array in C

Question

I am new to C. This code runs on a Flyport module and compiles on their own IDE but I should think my error should be easy to spot for anyone familiar with C.

I can't get this code to compile despite changing almost everything, what am I doing wrong?

char string_serial[50]="starting Value";    

if (string_serial[0] = "*")
        {   

            UARTWrite(2,"First Char OK");
            UARTWrite(2,"\r\n");

            else 

            UARTWrite(2,"First Char NOT OK");
            UARTWrite(2,"\r\n");

        }

If it's not obvious I am trying to check if character 0 in the array is *.

Thanks

Line 2: "*" isn't a character, but a string (const char [2] to be exact). Use single quotes for characters => '*'. Line 3: you have a braces problem, the correct syntax is => if (/* condition /*) { /* code if true */ } else { /* code if false /* } — Jean-Marie Comets
– Jean-Marie Comets, Commented Dec 1, 2012 at 13:27
You have to use == and * should be in single quotes like if (string_serial[0] == '*') and also the braces are to be kept in proper positions. if{/*if block*/} else {/*else block*/} — Praveen Vinny
– Praveen Vinny, Commented Dec 3, 2012 at 17:00

Desert Ice · Accepted Answer · 2012-12-01 13:42:16Z

6

The syntax for if/else conditions is wrong

The syntax should be

 if(condition)
  {
  }

  else
  {
  }

For your specific code it should be

if (string_serial[0] == '*')
        {   

            UARTWrite(2,"First Char OK");
            UARTWrite(2,"\r\n");
         }

else 
        {
            UARTWrite(2,"First Char NOT OK");
            UARTWrite(2,"\r\n");

        }

The = operator is assignment, it assigns the value (returning true when successful). What you need is == (for comparing).

Also use single quotes for characters as shown in the code above.

edited Dec 1, 2012 at 13:42

answered Dec 1, 2012 at 13:25

Desert Ice

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2 Comments

Simon_A Over a year ago

I think that is all good but I still get an error "syntax error at end of input" but maybe this is specific to the Flyport. It is great here I get an answer in 2 minutes, on the Flyport forum I can wait a week! Many thanks

Desert Ice Over a year ago

@Simon_A: syntax error at end of input is mostly because of unmatched flower brackets, check in your program whether each opened { has a matching }

Sergey Kalinichenko · Accepted Answer · 2012-12-01 13:24:46Z

2

You should replace double quotes with single quotes around "*", and use ==:

if (string_serial[0] == '*')

A single character enclosed in single quotes means "a character"; a single character enclosed in double quotes means "a one-character C string".

A single = means "assignment"; a double == means "compare".

answered Dec 1, 2012 at 13:24

Sergey Kalinichenko

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1 Comment

Victor Sorokin Over a year ago

Perhaps, changing = to == as well.

Ankur · Accepted Answer · 2012-12-02 08:43:24Z

1

You if structure is not correct

try this:

char string_serial[50]="starting Value";    

if (string_serial[0] == '*')
{   

   UARTWrite(2,"First Char OK");
}

else {

  UARTWrite(2,"First Char NOT OK");
  UARTWrite(2,"\r\n");

}

You need to change = to == and also get else block out of the if block

edited Dec 2, 2012 at 8:43

answered Dec 1, 2012 at 13:25

Ankur

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Comments

frogatto · Accepted Answer · 2016-08-15 10:56:08Z

1

'' is for a single char, but "" is for strings. The following line should work.

if (string_serial[0] == '*')

edited Aug 15, 2016 at 10:56

answered Dec 1, 2012 at 13:25

frogatto

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