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Is there a way to only print part of a string?
For example, if I have
char *str = "hello there";
Is there a way to just print "hello", keeping in mind that the substring I want to print is variable length, not always 5 chars?
I know that I could use a for loop and putchar or that I could copy the array and then add a null-terminator but I'm wondering if there's a more elegant way?
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You can use strncpy to duplicate the part of your string you want to print, but you'd have to take care to add a null terminator, as strncpy won't do that if it doesn't encounter one in the source string.
%c deals with a char (that is, a single character), whereas %s deals with a char * (that is, a pointer to an array of characters, hopefully null-terminated).
%s tells printf that the corresponding argument is to be treated as a string (in C terms, a 0-terminated sequence of char ); the type of the corresponding argument must be char * . %d tells printf that the corresponding argument is to be treated as an integer value; the type of the corresponding argument must be int .
So it turns out that, in C, it's actually impossible to write a proper "utility" substring function, that doesn't do any dynamic memory allocation, and that doesn't modify the original string. All of this is a consequence of the fact that C does not have a first-class string type.
Try this:
int length = 5;
printf("%*.*s", length, length, "hello there");
This will work too:
fwrite(str, 1, len, stdout);
It will not have the overhead of parsing the format specifier. Obviously, to adjust the beginning of the substring, you can simply add the index to the pointer.
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