How to sprintf an unsigned char?
This开发者_高级运维 doesn't work:
unsigned char foo;
foo = 0x123;
sprintf("the unsigned value is:%c",foo);
I get this error:
cannot convert parameter 2 from 'unsigned char' to 'char'
Before you go off looking at unsigned chars causing the problem, take a closer look at this line:
sprintf("the unsigned value is:%c",foo);
The first argument of sprintf is always the string to which the value will be printed. That line should look something like:
sprintf(str, "the unsigned value is:%c",foo);
Unless you meant printf instead of sprintf.
After fixing that, you can use %u in your format string to print out the value of an unsigned type.
Use printf()
formta string's %u
:
printf("%u", 'c');
EDIT
snprintf
is a little more safer. It's up to the developer to ensure the right buffer size is used.
Try this :
char p[255]; // example
unsigned char *foo;
...
foo[0] = 0x123;
...
snprintf(p, sizeof(p), " 0x%X ", (unsigned char)foo[0]);
I think your confused with the way sprintf
works. The first parameter is a string buffer, the second is a formatting string, and then the variables you want to output.
You should not use sprintf as it can easily cause a buffer overflow.
You should prefer snprintf (or _snprintf when programming with the Microsoft standard C library). If you have allocated the buffer on the stack in the local function, you can do:
char buffer[SIZE];
snprintf(buffer, sizeof(buffer), "...fmt string...", parameters);
The data may get truncated but that is definitely preferable to overflowing the buffer.
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