PRINTF(1) BSD General Commands Manual PRINTF(1)
printf -- formatted output
printf format [arguments ...]
printf 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 characters, 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
b, B, c, 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 ASCII 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 ANSI X3.159-1989
(``ANSI C89''). The characters and their meanings are as follows:
\e Write an <escape> character.
\a Write a <bell> character.
\b Write a <backspace> character.
\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 <double quote> character.
\\ Write a backslash character.
\num Write an 8-bit character whose ASCII value is the 1-, 2-, or 3-digit octal
\xxx Write an 8-bit character whose ASCII value is the 1- or 2-digit hexadecimal
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
``alternative form''. For b, c, d, and s formats, this option has no
effect. For the o format 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 e, E, 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
characters 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 characters to be printed from a string (b, B, and
s formats); if the digit string is missing, the precision is treated as zero;
A character which indicates the type of format to use (one of diouxXfwEgGbBcs).
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.
f 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.
eE The argument is printed in the style [-]d.ddde+-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.
An upper-case E is used for an 'E' format.
gG The argument is printed in style f or in style e (E) whichever gives full preci-
sion in minimum space.
b Characters from the string argument are printed with backslash-escape sequences
The following additional backslash-escape sequences are supported:
\c Causes printf to ignore any remaining characters in the string operand
containing it, any remaining string operands, and any additional charac-
ters in the format operand.
\0num Write an 8-bit character whose ASCII value is the 1-, 2-, or 3-digit
octal number num.
\^c Write the control character c. Generates characters `\000' through
`\037`, and `\177' (from `\^?').
\M-c Write the character c with the 8th bit set. Generates characters `\241'
\M^c Write the control character c with the 8th bit set. Generates charac-
ters `\200' through `\237`, and `\377' (from `\M^?').
B Characters from the string argument are printed with unprintable characters
backslash-escaped using the `\c',`\^c',`\M-c'or `\M^c', formats described above.
c The first character of argument is printed.
s Characters from the string argument are printed until the end is reached or
until the number of characters indicated by the precision specification is
reached; if the precision is omitted, all characters in the string are printed.
% Print a `%'; no argument is used.
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.
printf exits 0 on success, 1 on failure.
echo(1), printf(3), vis(3), printf(9)
The printf utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').
Support for the floating point formats and `*' as a field width and precision are optional
The behaviour of the %B format and the \', \", \xxx, \e and \[M][-|^]c escape sequences are
undefined in POSIX.
Since the floating point numbers are translated from ASCII to floating-point and then back
again, floating-point precision may be lost.
Hexadecimal character constants are restricted to, and should be specified as, two character
constants. This is contrary to the ISO C standard but does guarantee detection of the end
of the constant.
All formats which treat the argument as a number first convert the argument from its exter-
nal representation as a character string to an internal numeric representation, and then
apply the format to the internal numeric representation, producing another external charac-
ter string representation. One might expect the %c format to do likewise, but in fact it
To convert a string representation of a decimal, octal, or hexadecimal number into the cor-
responding character, two nested printf invocations may be used, in which the inner invoca-
tion converts the input to an octal string, and the outer invocation uses the octal string
as part of a format. For example, the following command outputs the character whose code is
0x0A, which is a newline in ASCII:
printf "$(printf "\\%o" "0x0A")"
BSD May 6, 2008 BSD