Printing with column padding when string features variables

Question

I've managed to print left-aligned padded columns when the output is static like this:

int col = 40;
printf("%-*s", col, "padded column");
printf("after the column\n");

I'm trying to do the same when the string is not static but formatted with a variable, ie:

int col = 40;
int var1 = 200;
printf("???", col, var1, " padded column");
printf("after the column\n");

Where the expected output would be, for example:

200 padded column                  after padded column

@user694733 Well my problem is that this printf("%-*s", col, "%d padded column", var1); is of course not valid, and this printf("%d%-*s", var1, col, " padded column"); doesn't generate a total width of col. — Juicy
– Juicy, Commented Sep 24, 2015 at 9:18

user694733 · Accepted Answer · 2015-09-24 09:27:42Z

1

You need to generate text in 2 parts:

char paddedColText[100];
snprintf(paddedColText, sizeof paddedColText, "%d padded column", var1);
printf("%-*s", col, paddedColText);

or, alternative:

col -= printf("%d", var1); // Returns string length
printf("%-*s", col, " padded column");

But keep in mind that printf can return negative error code, so checking the return value before using is a good idea.

answered Sep 24, 2015 at 9:21

user694733

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