printf(1) printf(1)
NAME [Toc] [Back]
printf - format and print arguments
SYNOPSIS [Toc] [Back]
printf format [arg ...]
DESCRIPTION [Toc] [Back]
printf writes formatted arguments to the standard output. The arg
arguments are formatted under control of the format operand.
format is a character string patterned after the formatting
conventions of printf(3S), and contains the following types of
objects:
characters Characters that are not escape sequences or
conversion specifications (as described
below) are copied to standard output.
escape sequences These are interpreted as non-graphic
characters:
\a alert
\b backspace
\f form-feed
\n new-line
\r carriage return
\t tab
\v vertical tab
\' single quote character
\\ backslash
\n the 8-bit character whose ASCII
code is the 1-, 2-, 3-, or 4-digit
octal number n, whose first
character must be a zero.
conversion specification
Specifies the output format of each argument
( see below).
Arguments following format are interpreted as strings if the
corresponding format is either c or s; otherwise they are treated
as constants.
Conversion Specifications [Toc] [Back]
Each conversion specification is introduced by the percent character
%. After the % character, the following can appear in the sequence
indicated:
flags Zero or more flags, in any order, which modify the
meaning of the conversion specification. The flag
characters and their meanings are:
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- The result of the conversion is leftjustified
within the field.
+ The result of a signed conversion
always begins with a sign, + or -.
<space> If the first character of a signed
conversion is not a sign, a space
character is prefixed to the result.
This means that if the space flag and
+ flag both appear, the space flag is
ignored.
# The value is to be converted to an
``alternate form''. For c, d, i, u,
and s conversions, this flag has no
effect. For o conversion, it
increases the precision to force the
first digit of the result to be a
zero. For x or X conversion, a nonzero
result has 0x or 0X prefixed to
it. For e, E, f, g, and G
conversions, the result always
contains a radix character, even if no
digits follow the radix character.
For g and G conversions, trailing
zeros are not removed from the result,
contrary to usual behavior.
field width An optional string of decimal digits to specify a
minimum field width. For an output field, if the
converted value has fewer characters than the field
width, it is padded on the left (or right, if the
left-adjustment flag, - has been given) to the field
width.
precision The precision specifies the minimum number of digits
to appear for the d, o, i, u, x, or X conversions
(the field is padded with leading zeros), the number
of digits to appear after the radix character for the
e and f conversions, the maximum number of
significant digits for the g conversion, or the
maximum number of characters to be printed from a
string in s conversion. The precision takes the form
of a period . followed by a decimal digit string. A
null digit string is treated as a zero.
conversion characters
A conversion character indicates the type of
conversion to be applied:
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d,i, The integer argument is printed a signed
o,u, decimal (d or i), unsigned octal (o),
x,X unsigned decimal (u), or unsigned
hexadecimal notation (x and X). The x
conversion uses the numbers and letters
0123456789abcdef, and the X conversion
uses the numbers and letters
0123456789ABCDEF. The precision
component of the argument specifies the
minimum number of digits to appear. If
the value being converted can be
represented in fewer digits than the
specified minimum, it is expanded with
leading zeroes. The default precision
is 1. The result of converting a zero
value with a precision of 0 is no
characters.
f The floating-point number argument is
printed in decimal notation in the style
[-]dddrddd, where the number of digits
after the radix character, r, is equal
to the precision specification. If the
precision is omitted from the argument,
six digits are output; if the precision
is explicitly 0, no radix appears.
e,E The floating-point-number argument is
printed in the style [-]drddde+_dd, where
there is one digit before the radix
character, and the number of digits
after it is equal to the precision.
When the precision is missing, six
digits are produced; if the precision is
0, no radix character appears. The E
conversion character produces a number
with E introducing the exponent instead
of e. The exponent always contains at
least two digits. However, if the value
to be printed requires an exponent
greater than two digits, additional
exponent digits are printed as
necessary.
g,G The floating-point-number argument is
printed in style f or e (or int style E
in the case of a G conversion
character), with the precision
specifying the number of significant
digits. The style used depends on the
value converted; style e is used only if
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printf(1) printf(1)
the exponent resulting from the
conversion is less than -h or greater
than or equal to the precision.
Trailing zeros are remove from the
result. A radix character appears only
if it is followed by a digit.
c The first character of the argument is
printed.
s The argument is taken to be a string,
and characters from the string are
printed until the end of the string or
the number of characters indicated by
the precision specification of the
argument is reached. If the precision
is omitted from the argument, it is
interpreted as infinite and all
characters up to the end of the string
are printed.
% Print a % character; no argument is
converted.
b Similar to the s conversion specifier,
except that the string can contain
backslash-escape sequences which are
then converted to the characters they
represent. \c will cause printf to
ignore any remaining characters in the
string operand containing it, any
remaining string operands and any
additional characters in the format
operand.
In no case does a nonexistent or insufficient field
width cause truncation of a field; if the result of a
conversion is wider than the field width, the field
is simply expanded to contain the conversion result.
EXTERNAL INFLUENCES [Toc] [Back]
Environment Variables
LC_CTYPE determines the interpretation of arg as single and/or multibyte
characters.
LC_MESSAGES determines the language in which messages are displayed.
If LC_CTYPE or LC_MESSAGES is not specified in the environment or is
set to the empty string, the value of LANG is used as a default for
each unspecified or empty variable. If LANG is not specified or is
set to the empty string, a default of "C" (see lang(5)) is used
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printf(1) printf(1)
instead of LANG.
If any internationalization variable contains an invalid setting,
printf behaves as if all internationalization variables are set to
"C". See environ(5).
International Code Set Support [Toc] [Back]
Single- and multi-byte character code sets are supported.
RETURN VALUE [Toc] [Back]
printf exits with one of the following values:
0 Successful completion;
>0 Errors occurred. The exit value is increased by one for
each error that occurred up to a maximum of 255.
DIAGNOSTICS [Toc] [Back]
If an argument cannot be converted into a form suitable for the
corresponding conversion specification, or for any other reason cannot
be correctly printed, a diagnostic message is printed to standard
error, the argument is output as a string form as it was given on the
command line, and the exit value is incremented.
EXAMPLES [Toc] [Back]
The following command prints the number 123 in octal, hexadecimal and
floating point formats in their alternate form
printf "%#o, %#x, %#X, %#f, %#g, %#e\n" 123 123 123 123 123 123
resulting in the following output
0173, 0x7b, 0X7B, 123.000000, 123.000, 1.230000e+02
Print the outputs with their corresponding field widths and precision:
printf "%.6d, %10.6d, %.6f, %.6e, %.6s\n" 123 123 1.23 123.4 MoreThanSix
resulting in the following output
000123, 000123, 1.230000, 1.234000e+02, MoreTh
SEE ALSO [Toc] [Back]
echo(1), printf(3S).
STANDARDS CONFORMANCE [Toc] [Back]
printf: XPG4, POSIX.2
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