Is there a way to have a variable sized padding in printf?
I have an integer which says how large the padding is:
void foo(int paddingSize) {
printf("%...MyText", paddingSize);
}
This should print out ### MyText where the paddingSize should decide the number of '#' symbols.
Yes, if you use * in your format string, it gets a number from the arguments:
printf ("%0*d\n", 3, 5);
will print "005".
Keep in mind you can only pad with spaces or zeros. If you want to pad with something else, you can use something like:
#include <stdio.h>
#include <string.h>
int main (void) {
char *s = "MyText";
unsigned int sz = 9;
char *pad = "########################################";
printf ("%.*s%s\n", (sz < strlen(s)) ? 0 : sz - strlen(s), pad, s);
}
This outputs ###MyText when sz is 9, or MyText when sz is 2 (no padding but no truncation). You may want to add a check for pad being too short.
You could write like this :
void foo(int paddingSize) {
printf ("%*s",paddingSize,"MyText");
}
printf( "%.*s", paddingSize, string );
For example:
const char *string = "12345678901234567890";
printf( "5:%.*s\n", 5, string );
printf( "8:%.*s\n", 8, string );
printf( "25:%.*s\n", 25, string );
displays:
5:12345
8:12345678
25:12345678901234567890
Be careful though - some compilers at least (and this may be a general C thing) will not always do what you want:
char *s = "four";
printf("%*.s\n", 5, s); // Note the "."
This prints 5 spaces;
char *s = "four";
printf("%*s\n", 3, s); // Note no "."
This prints all four characters "four"
. is precision and is supposed to be followed by either * or an optional decimal integer, which you're not doing. It is not clear to me what you're trying to do with the example because it is incorrect code. I suggest you read the man page or if you can find a copy of the standard it's also there. Yes printf(3) and scanf(3) families are complicated.better use std::cout
#include<iomanip>
#include<iostream>
using namespace std;
cout << setw(9) //set output width
<< setfill('#') // set fill character
<< setiosflags(ios_base::right) //put padding to the left
<< "MyText";
should produce:
###MyText
using namespace std; is frowned upon as it causes a lot of problems. But that's just an irrelevant aside.