Pico W Read Serial Input

I'm trying to read the input sent through the serial monitor but scanf does nothing and i can't figure out how to get getchar to do the same thing.

Here's a piece of code that I've tried to use that does not work on the pico. It does work on my pc.

char *readInput() {
    int i = 0;
    char ch;
    char *str = malloc(sizeof(char) * 1024);

    while((ch = getchar()) != '\n' && ch != EOF) {
	    if (i < 1024) {
		    str[i++] = ch;
		    printf("%c\n", ch); // For debugging. Returns the correct character.
	    }
    }
    printf("%s\n", str); // For debugging. Returns nothing.
    str[i] = '
char *readInput() {
int i = 0;
char ch;
char *str = malloc(sizeof(char) * 1024);
while((ch = getchar()) != '\n' && ch != EOF) {
if (i < 1024) {
str[i++] = ch;
printf("%c\n", ch); // For debugging. Returns the correct character.
}
}
printf("%s\n", str); // For debugging. Returns nothing.
str[i] = '\0';
return str;
}
';

    return str;
}

It looks like it just tries to read until it gets to the 1024th character.

Also I've read somewhere that scanf doesn't work on the Pico but some people say it works so i don't even know anymore.

malloc()'s result is discarded:

char *str = malloc(sizeof(char) * 1024);

malloc() returns a NULL pointer to indicate failure, which it can and does. Its return value should always be checked. If it returns NULL, subsequent operations would be dereferencing and writing to a NULL pointer.

Aside: sizeof (char) is defined to be 1, so you can leave that out.

char *str = malloc(1024);
/* Add */
if (!str) {
   /* malloc() failed to allocate memory.
    * Handle error here.
    */
}

Off-by-one error:

if (i < 1024)

doesn't leave room for the null-byte.

getchar() returns an int:

char ch;

while((ch = getchar()) != '\n' && ch != EOF)

> If the integer value returned by getchar() is stored into a
> variable of type char and then compared against the integer
> constant EOF, the comparison may never succeed, because sign-
> extension of a variable of type char on widening to integer is
> implementation-defined.

Undefined behaviour:

printf("%s\n", str); // For debugging. Returns nothing.

The %s format specifier expects a string. str is not a string. The call to printf() would invoke undefined behaviour.

Move

str[i] = '
str[i] = '\0';
';

before the call to printf().

Writing to out of bounds memory:

    str[i] = '
    str[i] = '\0';
';

The value of i is 1024 when the while loop exits. You only allocated memory for 1023 characters.

Minor:

char *readInput()

indicates that readInput takes an unspecified number and type of arguments.

char *readInput (void)

doesn't.

The serial monitor I was using was just broken and it didn't display/send things correctly. Changing it to arduino's one fixed the problem and I can use scanf now.