PRINTF(1) BSD General Commands Manual PRINTF(1)
printf -- formatted output
printf format [arguments ...]
The printf utility formats and prints its arguments, after the first, under control of the
format. The format is a character string which contains three types of objects: plain char-
acters, which are simply copied to standard output, character escape sequences which are
converted and copied to the standard output, and format specifications, each of which causes
printing of the next successive argument.
The arguments after the first are treated as strings if the corresponding format is either
c, b or s; otherwise it is evaluated as a C constant, with the following extensions:
o A leading plus or minus sign is allowed.
o If the leading character is a single or double quote, the value is the character
code of the next character.
The format string is reused as often as necessary to satisfy the arguments. Any extra for-
mat specifications are evaluated with zero or the null string.
Character escape sequences are in backslash notation as defined in the ANSI X3.159-1989
(``ANSI C89''), with extensions. The characters and their meanings are as follows:
\a Write a <bell> character.
\b Write a <backspace> character.
\c Ignore remaining characters in this string.
\f Write a <form-feed> character.
\n Write a <new-line> character.
\r Write a <carriage return> character.
\t Write a <tab> character.
\v Write a <vertical tab> character.
\' Write a <single quote> character.
\\ Write a backslash character.
\num Write a byte whose value is the 1-, 2-, or 3-digit octal number num. Multi-
byte characters can be constructed using multiple \num sequences.
Each format specification is introduced by the percent character (``%''). The remainder of
the format specification includes, in the following order:
Zero or more of the following flags:
# A `#' character specifying that the value should be printed in an ``alter-
nate form''. For b, c, d, s and u formats, this option has no effect. For
the o formats the precision of the number is increased to force the first
character of the output string to a zero. For the x (X) format, a non-zero
result has the string 0x (0X) prepended to it. For a, A, e, E, f, F, g and
G formats, the result will always contain a decimal point, even if no digits
follow the point (normally, a decimal point only appears in the results of
those formats if a digit follows the decimal point). For g and G formats,
trailing zeros are not removed from the result as they would otherwise be;
- A minus sign `-' which specifies left adjustment of the output in the indi-
+ A `+' character specifying that there should always be a sign placed before
the number when using signed formats.
' ' A space specifying that a blank should be left before a positive number for
a signed format. A `+' overrides a space if both are used;
0 A zero `0' character indicating that zero-padding should be used rather than
blank-padding. A `-' overrides a `0' if both are used;
An optional digit string specifying a field width; if the output string has fewer
bytes than the field width it will be blank-padded on the left (or right, if the
left-adjustment indicator has been given) to make up the field width (note that a
leading zero is a flag, but an embedded zero is part of a field width);
An optional period, '.', followed by an optional digit string giving a precision
which specifies the number of digits to appear after the decimal point, for e and f
formats, or the maximum number of bytes to be printed from a string; if the digit
string is missing, the precision is treated as zero;
A character which indicates the type of format to use (one of diouxXfFeEgGaAcsb).
The uppercase formats differ from their lowercase counterparts only in that the out-
put of the former is entirely in uppercase. The floating-point format specifiers
(fFeEgGaA) may be prefixed by an L to request that additional precision be used, if
A field width or precision may be '*' instead of a digit string. In this case an argument
supplies the field width or precision.
The format characters and their meanings are:
diouXx The argument is printed as a signed decimal (d or i), unsigned octal, unsigned
decimal, or unsigned hexadecimal (X or x), respectively.
fF The argument is printed in the style `[-]ddd.ddd' where the number of d's after
the decimal point is equal to the precision specification for the argument. If
the precision is missing, 6 digits are given; if the precision is explicitly 0,
no digits and no decimal point are printed. The values infinity and NaN are
printed as 'inf' and 'nan', respectively.
eE The argument is printed in the style e '[-d.ddd+-dd]' where there is one digit
before the decimal point and the number after is equal to the precision specifi-
cation for the argument; when the precision is missing, 6 digits are produced.
The values infinity and NaN are printed as 'inf' and 'nan', respectively.
gG The argument is printed in style f (F) or in style e (E) whichever gives full
precision in minimum space.
aA The argument is printed in style '[-h.hhh+-pd]' where there is one digit before
the hexadecimal point and the number after is equal to the precision specifica-
tion for the argument; when the precision is missing, enough digits are produced
to convey the argument's exact double-precision floating-point representation.
The values infinity and NaN are printed as 'inf' and 'nan', respectively.
c The first byte of argument is printed.
s Bytes from the string argument are printed until the end is reached or until the
number of bytes indicated by the precision specification is reached; however if
the precision is 0 or missing, the string is printed entirely.
b As for s, but interpret character escapes in backslash notation in the string
argument. The permitted escape sequences are slightly different in that octal
escapes are \0num instead of \num.
n$ Allows reordering of the output according to argument.
% Print a `%'; no argument is used.
The decimal point character is defined in the program's locale (category LC_NUMERIC).
In no case does a non-existent or small field width cause truncation of a field; padding
takes place only if the specified field width exceeds the actual width.
Some shells may provide a builtin printf command which is similar or identical to this util-
ity. Consult the builtin(1) manual page.
The printf utility exits 0 on success, and >0 if an error occurs.
The traditional BSD behavior of converting arguments of numeric formats not beginning with a
digit to the ASCII code of the first character is not supported.
builtin(1) , echo(1) , sh(1) , printf(3)
The printf command is expected to be compatible with the IEEE Std 1003.2 (``POSIX.2'') spec-
The printf command appeared in 4.3BSD-Reno. It is modeled after the standard library func-
tion, printf(3) .
ANSI hexadecimal character constants were deliberately not provided.
Trying to print a dash ("-") as the first character causes printf to interpret the dash as a
program argument. -- must be used before format.
If the locale contains multibyte characters (such as UTF-8), the c format and b and s for-
mats with a precision may not operate as expected.
Since the floating point numbers are translated from ASCII to floating-point and then back
again, floating-point precision may be lost. (By default, the number is translated to an
IEEE-754 double-precision value before being printed. The L modifier may produce additional
precision, depending on the hardware platform.)
The escape sequence \000 is the string terminator. When present in the argument for the b
format, the argument will be truncated at the \000 character.
Multibyte characters are not recognized in format strings (this is only a problem if '%' can
appear inside a multibyte character).
BSD April 21, 2014 BSD