What does the %*s format specifier mean?

Aamir picture Aamir · Jun 16, 2009 · Viewed 50.7k times · Source

In some code that I have to maintain, I have seen a format specifier %*s . Can anybody tell me what this is and why it is used?

An example of its usage is like:

fprintf(outFile, "\n%*s", indent, "");

Answer

akappa picture akappa · Jun 16, 2009

It's used to specify, in a dynamic way, what the width of the field is:

  • The width is not specified in the format string, but as an additional integer value argument preceding the argument that has to be formatted.

so "indent" specifies how much space to allocate for the string that follows it in the parameter list.

So,

printf("%*s", 5, "");

is the same as

printf("%5s", "");

It's a nice way to put some spaces in your file, avoiding a loop.