 @@ -1,411 +1,418 @@
-.\"	$NetBSD: printf.1,v 1.25 2014/04/13 01:45:34 snj Exp $
+.\"	$NetBSD: printf.1,v 1.26 2018/03/12 00:42:05 dholland Exp $
 .\"
 .\" Copyright (c) 1989, 1990, 1993
 .\"	The Regents of the University of California.  All rights reserved.
 .\"
 .\" This code is derived from software contributed to Berkeley by
 .\" the Institute of Electrical and Electronics Engineers, Inc.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\" 3. Neither the name of the University nor the names of its contributors
 .\"    may be used to endorse or promote products derived from this software
 .\"    without specific prior written permission.
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 .\" ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
 .\"	from: @(#)printf.1	8.1 (Berkeley) 6/6/93
 .\"
-.Dd May 6, 2008
+.Dd March 11, 2018
 .Dt PRINTF 1
 .Os
 .Sh NAME
 .Nm printf
 .Nd formatted output
 .Sh SYNOPSIS
 .Nm
 .Ar format
 .Op Ar arguments  ...
 .Sh DESCRIPTION
 .Nm
 formats and prints its arguments, after the first, under control
 of the
 .Ar format  .
 The
 .Ar 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
 .Ar argument  .
 .Pp
 The
 .Ar arguments
 after the first are treated as strings if the corresponding format is
 either
 .Cm b ,
 .Cm B ,
 .Cm c ,
 or
 .Cm s ;
 otherwise it is evaluated as a C constant, with the following extensions:
 .Pp
 .Bl -bullet -offset indent -compact
 .It
 A leading plus or minus sign is allowed.
 .It
 If the leading character is a single or double quote, the value is the
 .Tn ASCII
 code of the next character.
 .El
 .Pp
 The format string is reused as often as necessary to satisfy the
 .Ar arguments  .
 Any extra format specifications are evaluated with zero or the null
 string.
 .Pp
 Character escape sequences are in backslash notation as defined in
 .St -ansiC .
 The characters and their meanings are as follows:
 .Bl -tag -width Ds -offset indent
 .It Cm \ee
 Write an
 .Aq escape
 character.
 .It Cm \ea
 Write a
 .Aq bell
 character.
 .It Cm \eb
 Write a
 .Aq backspace
 character.
 .It Cm \ef
 Write a
 .Aq form-feed
 character.
 .It Cm \en
 Write a
 .Aq new-line
 character.
 .It Cm \er
 Write a
 .Aq carriage return
 character.
 .It Cm \et
 Write a
 .Aq tab
 character.
 .It Cm \ev
 Write a
 .Aq vertical tab
 character.
 .It Cm \e\'
 Write a
 .Aq single quote
 character.
 .It Cm \e"
 Write a
 .Aq double quote
 character.
 .It Cm \e\e
 Write a backslash character.
 .It Cm \e Ns Ar num
 Write an 8\-bit character whose
 .Tn ASCII
 value is the 1\-, 2\-, or 3\-digit octal number
 .Ar num .
 .It Cm \ex Ns Ar xx
 Write an 8\-bit character whose
 .Tn ASCII
 value is the 1\- or 2\-digit hexadecimal number
 .Ar xx .
 .El
 .Pp
 Each format specification is introduced by the percent character
 .Pq Dq \&% .
 The remainder of the format specification includes,
 in the following order:
 .Bl -tag -width Ds
 .It Zero or more of the following flags :
 .Bl -tag -width Ds
 .It Cm #
+A
 .Sq #
 character specifying that the value should be printed in an
 .Dq alternative form .
 For
 .Cm b ,
 .Cm c ,
 .Cm d ,
 and
 .Cm s
 formats, this option has no effect.
 For the
 .Cm o
 format the precision of the number is increased to force the first
 character of the output string to a zero.
 For the
 .Cm x
 .Pq Cm X
 format, a non-zero result has the string
 .Li 0x
 .Pq Li 0X
 prepended to it.
 For
 .Cm e ,
 .Cm E ,
 .Cm f ,
 .Cm g ,
 and
 .Cm 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
 .Cm g
 and
 .Cm G
 formats, trailing zeros are not removed from the result as they
 would otherwise be.
 .\" I turned this off - decided it isn't a valid use of '#'
 .\" For the
 .\" .Cm B
 .\" format, backslash-escape sequences are expanded first;
 .It Cm \&\-
 A minus sign
 .Sq \-
 which specifies
 .Em left adjustment
 of the output in the indicated field;
 .It Cm \&+
+A
 .Sq \&+
 character specifying that there should always be
 a sign placed before the number when using signed formats.
 .It Sq \&\ \&
 A space specifying that a blank should be left before a positive number
 for a signed format.
+A
 .Sq \&+
 overrides a space if both are used;
 .It Cm \&0
 A zero `0' character indicating that zero-padding should be used
 rather than blank-padding.
+A
 .Sq \-
 overrides a
 .Sq \&0
 if both are used;
 .El
 .It Field Width :
 An optional digit string specifying a
 .Em 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);
 .It Precision :
 An optional period,
 .Sq Cm \&. ,
 followed by an optional digit string giving a
 .Em precision
 which specifies the number of digits to appear after the decimal point,
 for
 .Cm e
 and
 .Cm f
 formats, or the maximum number of characters to be printed
 from a string
 .Sm off
 .Pf ( Cm b ,
 .Sm on
 .Cm B ,
 and
 .Cm s
 formats); if the digit string is missing, the precision is treated
 as zero;
 .It Format :
 A character which indicates the type of format to use (one of
 .Cm diouxXfwEgGbBcs ) .
 .El
 .Pp
 A field width or precision may be
 .Sq Cm \&*
 instead of a digit string.
 In this case an
 .Ar argument
 supplies the field width or precision.
 .Pp
 The format characters and their meanings are:
 .Bl -tag -width Fl
 .It Cm diouXx
 The
 .Ar argument
 is printed as a signed decimal (d or i), unsigned octal, unsigned decimal,
 or unsigned hexadecimal (X or x), respectively.
 .It Cm f
 The
 .Ar argument
 is printed in the style
 .Sm off
 .Pf [\-]ddd Cm \&. No ddd
 .Sm on
 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.
 .It Cm eE
 The
 .Ar argument
 is printed in the style
 .Sm off
 .Pf [\-]d Cm \&. No ddd Cm e No \*(Pmdd
 .Sm on
 where there
 is one digit before the decimal 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
 .Sq E
 format.
 .It Cm gG
 The
 .Ar argument
 is printed in style
 .Cm f
 or in style
 .Cm e
 .Pq Cm E
 whichever gives full precision in minimum space.
 .It Cm b
 Characters from the string
 .Ar argument
 are printed with backslash-escape sequences expanded.
 .Pp
 The following additional backslash-escape sequences are supported:
 .Bl -tag -width Ds
 .It Cm \ec
 Causes
 .Nm
 to ignore any remaining characters in the string operand containing it,
 any remaining string operands, and any additional characters in
 the format operand.
 .It Cm \e0 Ns Ar num
 Write an 8\-bit character whose
 .Tn ASCII
 value is the 1\-, 2\-, or 3\-digit
 octal number
 .Ar num .
 .It Cm \e^ Ns Ar c
 Write the control character
 .Ar c .
 Generates characters `\e000' through `\e037`, and `\e177' (from `\e^?').
 .It Cm \eM\- Ns Ar c
 Write the character
 .Ar c
 with the 8th bit set.
 Generates characters `\e241' through `\e376`.
 .It Cm \eM^ Ns Ar c
 Write the control character
 .Ar c
 with the 8th bit set.
 Generates characters `\e200' through `\e237`, and `\e377' (from `\eM^?').
 .El
 .It Cm B
 Characters from the string
 .Ar argument
 are printed with unprintable characters backslash-escaped using the
 .Sm off
 .Pf ` Cm \e Ar c No ',
 .Pf ` Cm \e^ Ar c No ',
 .Pf ` Cm \eM\- Ar c No '
 or
 .Pf ` Cm \eM^ Ar c No ',
 .Sm on
 formats described above.
 .It Cm c
 The first character of
 .Ar argument
 is printed.
 .It Cm s
 Characters from the string
 .Ar 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.
 .It Cm \&%
 Print a `%'; no argument is used.
 .El
 .Pp
 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.
 .Pp
 If the first character of
 .Ar format
 is a dash,
 .Ar format
 must be preceded by a word consisting of two dashes (--) to prevent it
 from being interpreted as an option string.
 .Sh EXIT STATUS
 .Ex -std
 .Sh SEE ALSO
 .Xr echo 1 ,
 .Xr printf 3 ,
 .Xr vis 3 ,
 .Xr printf 9
 .Sh STANDARDS
 The
 .Nm
 utility conforms to
 .St -p1003.1-2001 .
 .Pp
 Support for the floating point formats and `*' as a field width and precision
 are optional in POSIX.
 .Pp
 The behaviour of the %B format and the \e', \e", \exxx, \ee and
 \e[M][\-|^]c escape sequences are undefined in POSIX.
 .Sh BUGS
 Since the floating point numbers are translated from
 .Tn ASCII
 to floating-point and
 then back again, floating-point precision may be lost.
 .Pp
 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.
 .Sh NOTES
 All formats which treat the
 .Ar argument
 as a number first convert the
 .Ar argument
 from its external representation as a character string
 to an internal numeric representation, and then apply the
 format to the internal numeric representation, producing
 another external character string representation.
 One might expect the
 .Cm \&%c
 format to do likewise, but in fact it does not.
 .Pp
 To convert a string representation of a decimal, octal, or hexadecimal
 number into the corresponding character, two nested
 .Nm
 invocations may be used, in which the inner invocation
 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:
 .Pp
 .Dl printf \&"$(printf \&"\e\e%o" \&"0x0A")"