PRINTF(1) BSD General Commands Manual PRINTF(1)
NAME
printf -- formatted output
SYNOPSIS
printf format [arguments ...]
DESCRIPTION
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 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, c or s;
otherwise it is evaluated as a C constant, with the following extensions:
oo A leading plus or minus sign is allowed.
oo 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 format specifi-cations specifications
cations 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 backslash character.
\num Write an 8-bit character whose ASCII value is the 1-, 2-, or 3-digit octal number num.
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 c, d, and s, 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 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 indicated field;
+ 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-pad-ding. blank-padding.
ding. A `-' overrides a `0' if both are used;
Field Width:
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);
Precision:
An optional period, `.', followed by an optional digit string giving a precision which speci-fies specifies
fies the number of digits to appear after the decimal point, for e and f formats, or the maxi-mum maximum
mum number of characters to be printed from a string; if the digit string is missing, the pre-cision precision
cision is treated as zero;
Format:
A character which indicates the type of format to use (one of diouxXfwEgGbcs).
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 miss-ing, missing,
ing, 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 dec-imal decimal
imal point and the number after is equal to the precision specification 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 precision in min-imum minimum
imum space.
b Characters from the string argument are printed with backslash-escape sequences expanded.
c The first character of argument is printed.
s Characters from the string argument are printed until the end is reached or until the num-ber number
ber of characters indicated by the precision specification is reached; however if the pre-cision precision
cision is 0 or missing, 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.
RETURN VALUES
printf exits 0 on success, 1 on failure.
SEE ALSO
echo(1), printf(3)
STANDARDS
The printf utility mostly conforms to IEEE Std 1003.2-1992 (``POSIX.2'').
BUGS
Since the floating point numbers are translated from ASCII to floating-point and then back again,
floating-point precision may be lost.
Parsing of - arguments is also somewhat different from printf(3), where unknown arguments are simply
printed instead of being flagged as errors.
BSD November 5, 1993 BSD
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