Function: format
format is a function defined in editfns.c.
Signature
(format STRING &rest OBJECTS)
Documentation
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, or the argument explicitly specified:
%s means produce a string argument. Actually, produces any object with princ.
%d or %i means produce a signed number in decimal.
%b means produce a number in binary.
%B is like %b, but %#B uses upper case.
%o means produce a number in octal.
%x means produce a number in hex.
%X is like %x, but uses upper case.
%e means produce a number in exponential notation.
%f means produce a number in decimal-point notation.
%g means produce a number in exponential notation if the exponent would be
less than -4 or greater than or equal to the precision (default: 6);
otherwise it produces in decimal-point notation.
%c means produce a number as a single character.
%S means produce any object as an s-expression (using prin1).
The argument used for %d, %i, %o, %x, %e, %f, %g or %c must be a number. Use %% to put a single % into the output.
A %-sequence other than %% may contain optional field number, flag, width, and precision specifiers, as follows:
%<field><flags><width><precision>character
where field is [0-9]+ followed by a literal dollar "$", flags is
[+ #0-]+, width is [0-9]+, and precision is a literal period "."
followed by [0-9]+.
If a %-sequence is numbered with a field with positive value N, the Nth argument is substituted instead of the next one. A format can contain either numbered or unnumbered %-sequences but not both, except that %% can be mixed with numbered %-sequences.
The + flag character inserts a + before any nonnegative number, while a space inserts a space before any nonnegative number; these flags affect only numeric %-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 %b, %B, %o, %x,
%X, %e, %f, and %g sequences: for %b and %B, it prefixes nonzero results
with "0b" or "0B"; for %o, it ensures that the result begins with
"0"; for %x and %X, it prefixes nonzero results with "0x" or "0X";
for %e and %f, it causes a decimal point to be included even if the
precision is zero; for %g, it causes a decimal point to be
included even if the precision is zero, and also forces trailing
zeros after the decimal point to be left in place.
The width specifier supplies a lower limit for the length of the produced 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, %b, %o, %x, %e, %f, and %g.
For %e and %f 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 %g, the precision specifies how many significant digits to produce; zero or omitted are treated as 1. For %s and %S, the precision specifier truncates the string to the given width.
Text properties, if any, are copied from the format-string to the produced text.
Other relevant functions are documented in the string group.
Probably introduced at or before Emacs version 1.10.
Shortdoc
;; string
(format "This number is %d" 4)
=> "This number is 4"Source Code
// Defined in /usr/src/emacs/src/editfns.c
{
return styled_format (nargs, args, false);
}