A format specifier starts with the character ‘%’ and ends with
a format-control letter—it tells the
how to output one item. The format-control letter specifies what kind
of value to print. The rest of the format specifier is made up of
optional modifiers that control how to print the value, such as
the field width. Here is a list of the format-control letters:
NOTE: The POSIX standard says the first character of a string is printed. In locales with multibyte characters, gawk attempts to convert the leading bytes of the string into a valid wide character and then to print the multibyte encoding of that character. Similarly, when printing a numeric value, gawk allows the value to be within the numeric range of values that can be held in a wide character.
Other awk versions generally restrict themselves to printing the first byte of a string or to numeric values within the range of a single byte (0–255).
printf "%4.3e\n", 1950
prints ‘1.950e+03’, with a total of four significant figures, three of
which follow the decimal point.
(The ‘4.3’ represents two modifiers,
discussed in the next subsection.)
‘%E’ uses ‘E’ instead of ‘e’ in the output.
printf "%4.3f", 1950
prints ‘1950.000’, with a total of four significant figures, three of which follow the decimal point. (The ‘4.3’ represents two modifiers, discussed in the next subsection.)
On systems supporting IEEE 754 floating point format, values
infinity are formatted as
‘-inf’ or ‘-infinity’,
and positive infinity as
‘inf’ and ‘infinity’.
The special “not a number” value formats as ‘-nan’ or ‘nan’.
The ‘%F’ format is a POSIX extension to ISO C; not all systems
support it. On those that don't, gawk uses ‘%f’ instead.
NOTE: When using the integer format-control letters for values that are outside the range of the widest C integer type, gawk switches to the ‘%g’ format specifier. If --lint is provided on the command line (see Options), gawk warns about this. Other versions of awk may print invalid values or do something else entirely. (d.c.)