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printf

printf prints text built from a format string. The format string is printed literally, except that escape sequences become characters and substitution fields are replaced by the arguments that follow.

printf format [argument...]

$ printf 'the letter %X comes before %X\n' 10 11
the letter A comes before B

Where echo prints arguments as-is, printf gives you control: padding, column widths, number bases, fixed decimal places. It is the command for output that has to line up or be exact.

printf writes only what the format string says — there is no automatic trailing newline. Include \n yourself where you want one.

Escape sequences

The format string interprets these backslash sequences:

Sequence Character
\\ Backslash.
\n \t \r Newline, tab, carriage return.
\b \f \v \a Backspace, form feed, vertical tab, alert.
\e Escape.
\NNN The byte with octal value NNN.
\xHH The byte with hexadecimal value HH.
\uHHHH, \UHHHHHHHH A Unicode character by hexadecimal code point.
%% A literal %.

Substitution fields

A field begins with % and is replaced by the next argument, formatted accordingly.

Field Formats the argument as…
%s a string.
%b a string, with backslash escapes in it interpreted.
%q a string, quoted so it is safe to reuse as shell input.
%c a single character.
%d, %i a signed integer.
%u an unsigned integer.
%x, %X an unsigned integer in hexadecimal (lower- or upper-case).
%o an unsigned integer in octal.
%f, %F a decimal floating-point number.
%e, %E a number in scientific notation.
%g, %G whichever of decimal or scientific notation is shorter.

Width and precision

Between the % and the field letter you may put two numbers — %[width][.precision]field:

  • width — the minimum number of columns. Output narrower than this is padded with leading spaces; a negative width pads on the right instead.
  • precision — after a .; its meaning depends on the field. For a string it is a maximum length; for an integer, a minimum digit count (zero-padded); for a float, the number of decimal places.
$ printf '%-10s %5.2f\n' apples 3.1
apples         3.10

Reusing the format string

If more arguments are supplied than the format string has fields, printf repeats the format string until the arguments run out. If there are too few, the leftover fields default to an empty string (or 0 for a number).

$ printf '%s: %d\n' alpha 1 beta 2 gamma 3
alpha: 1
beta: 2
gamma: 3

Exit status

Code Meaning
0 Success.
1 A missing operand, a bad format string, or a write failure.

See also