format

format is a built-in function in `C source code'.

(format STRING &rest OBJECTS)

Format a string out of a format-string and arguments.
The first argument is a format control string.
The other arguments are substituted into it to make the result, a string.

The format control string may contain %-sequences meaning to substitute
the next available argument:

%s means print a string argument. Actually, prints any object, with `princ'.
%d means print as number in decimal (%o octal, %x hex).
%X is like %x, but uses upper case.
%e means print a number in exponential notation.
%f means print a number in decimal-point notation.
%g means print a number in exponential notation
or decimal-point notation, whichever uses fewer characters.
%c means print a number as a single character.
%S means print any object as an s-expression (using `prin1').

The argument used for %d, %o, %x, %e, %f, %g or %c must be a number.
Use %% to put a single % into the output.

A %-sequence may contain optional flag, width, and precision
specifiers, as follows:

%<flags><width><precision>character

where flags is [+ #-0]+, width is [0-9]+, and precision is .[0-9]+

The + flag character inserts a + before any positive number, while a
space inserts a space before any positive number; these flags only
affect %d, %e, %f, and %g sequences, and the + flag takes precedence.
The - and 0 flags affect the width specifier, as described below.

The # flag means to use an alternate display form for %o, %x, %X, %e,
%f, and %g sequences: for %o, it ensures that the result begins with
"0"; for %x and %X, it prefixes the result with "0x" or "0X";
for %e, %f, and %g, it causes a decimal point to be included even if
the precision is zero.

The width specifier supplies a lower limit for the length of the
printed representation. The padding, if any, normally goes on the
left, but it goes on the right if the - flag is present. The padding
character is normally a space, but it is 0 if the 0 flag is present.
The 0 flag is ignored if the - flag is present, or the format sequence
is something other than %d, %e, %f, and %g.

For %e, %f, and %g sequences, the number after the "." in the
precision specifier says how many decimal places to show; if zero, the
decimal point itself is omitted. For %s and %S, the precision
specifier truncates the string to the given width.