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.\"
.TH PRINTF 3C "Aug 19, 2020"
.SH NAME
printf, fprintf, sprintf, snprintf, asprintf \- print formatted output
.SH SYNOPSIS
.nf
#include <stdio.h>

\fBint\fR \fBprintf\fR(\fBconst char *restrict\fR \fIformat\fR,
     \fB/*\fR \fIargs\fR*/ ...);
.fi

.LP
.nf
\fBint\fR \fBfprintf\fR(\fBFILE *restrict\fR \fIstream\fR, \fBconst char *restrict\fR \fIformat\fR,
     \fB/*\fR \fIargs\fR*/ ...);
.fi

.LP
.nf
\fBint\fR \fBsprintf\fR(\fBchar *restrict\fR \fIs\fR, \fBconst char *restrict\fR \fIformat\fR,
     \fB/*\fR \fIargs\fR*/ ...);
.fi

.LP
.nf
\fBint\fR \fBsnprintf\fR(\fBchar *restrict\fR \fIs\fR, \fBsize_t\fR \fIn\fR,
     \fBconst char *restrict\fR \fIformat\fR, \fB/*\fR \fIargs\fR*/ ...);
.fi

.LP
.nf
\fBint\fR \fBasprintf\fR(\fBchar **\fR \fIret\fR, \fBconst char *restrict\fR \fIformat\fR,
     \fB/*\fR \fIargs\fR*/ ...);
.fi

.SH DESCRIPTION
The \fBprintf()\fR function places output on the standard output stream
\fBstdout\fR.
.sp
.LP
The \fBfprintf()\fR function places output on on the named output stream
\fIstream\fR.
.sp
.LP
The \fBsprintf()\fR function places output, followed by the null byte
(\fB\e0\fR), in consecutive bytes starting at \fIs\fR; it is the user's
responsibility to ensure that enough storage is available.
.sp
.LP
The \fBsnprintf()\fR function is identical to \fBsprintf()\fR with the addition
of the argument \fIn\fR, which specifies the size of the buffer referred to by
\fIs\fR. If \fIn\fR is 0, nothing is written and \fIs\fR can be a null pointer.
Otherwise, output bytes beyond the \fIn\fR-1st are discarded instead of being
written to the array and a null byte is written at the end of the bytes
actually written into the array.
.sp
.LP
The \fBasprintf()\fR function is the same as the \fBsprintf()\fR function
except that it returns, in the \fIret\fR argument, a pointer to a buffer
sufficiently large to hold the output string. This pointer should be passed to
\fBfree\fR(3C) to release the allocated storage when it is no longer needed. If
sufficient space cannot be allocated, the \fBasprintf()\fR function returns -1
and sets \fIret\fR to be a \fINULL\fR pointer.
.sp
.LP
Each of these functions converts, formats, and prints its arguments under
control of the \fIformat\fR. The \fIformat\fR is a character string, beginning
and ending in its initial shift state, if any. The \fIformat\fR is composed of
zero or more directives: \fBordinary characters\fR, which are simply copied to
the output stream and \fBconversion specifications\fR, each of which results in
the fetching of zero or more arguments. The results are undefined if there are
insufficient arguments for the \fIformat\fR. If the \fIformat\fR is exhausted
while arguments remain, the excess arguments are evaluated but are otherwise
ignored.
.sp
.LP
Conversions can be applied to the \fIn\fRth argument after the \fIformat\fR in
the argument list, rather than to the next unused argument. In this case, the
conversion specifier \fB%\fR (see below) is replaced by the sequence
\fB%\fR\fIn\fR\fB$\fR, where \fIn\fR is a decimal integer in the range [1,
\fBNL_ARGMAX\fR], giving the position of the argument in the argument list.
This feature provides for the definition of format strings that select
arguments in an order appropriate to specific languages (see the \fBEXAMPLES\fR
section).
.sp
.LP
In format strings containing the \fB%\fR\fIn\fR\fB$\fR form of conversion
specifications, numbered arguments in the argument list can be referenced from
the format string as many times as required.
.sp
.LP
In format strings containing the \fB%\fR form of conversion specifications,
each argument in the argument list is used exactly once.
.sp
.LP
All forms of the \fBprintf()\fR functions allow for the insertion of a
language-dependent radix character in the output string. The radix character is
defined by the program's locale (category \fBLC_NUMERIC\fR). In the POSIX
locale, or in a locale where the radix character is not defined, the radix
character defaults to a period (\fB\&.\fR).
.SS "Conversion Specifications"
Each conversion specification is introduced by the \fB%\fR character or by the
character sequence \fB%\fR\fIn\fR\fB$\fR, after which the following appear in
sequence:
.RS +4
.TP
.ie t \(bu
.el o
An optional field, consisting of a decimal digit string followed by a \fB$\fR,
specifying the next argument to be converted. If this field is not provided,
the \fIargs\fR following the last argument converted will be used.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Zero or more \fIflags\fR (in any order), which modify the meaning of the
conversion specification.
.RE
.RS +4
.TP
.ie t \(bu
.el o
An optional minimum \fIfield width\fR. If the converted value has fewer bytes
than the field width, it will be padded with spaces by default on the left; it
will be padded on the right, if the left-adjustment flag (\fB\(hy\fR),
described below, is given to the field width. The field width takes the form of
an asterisk (*), described below, or a decimal integer.
.sp
If the conversion specifier is \fBs\fR, a standard-conforming application (see
\fBstandards\fR(7)) interprets the field width as the minimum number of bytes
to be printed; an application that is not standard-conforming interprets the
field width as the minimum number of columns of screen display. For an
application that is not standard-conforming, \fB%10s\fR means if the converted
value has a screen width of 7 columns, 3 spaces would be padded on the right.
.sp
If the format is \fB%ws\fR, then the field width should be interpreted as the
minimum number of columns of screen display.
.RE
.RS +4
.TP
.ie t \(bu
.el o
An optional \fIprecision\fR that gives the minimum number of digits to appear
for the \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, and \fBX\fR conversions
(the field is padded with leading zeros); the number of digits to appear after
the radix character for the \fBa\fR, \fBA\fR, \fBe\fR, \fBE\fR, \fBf\fR, and
\fBF\fR conversions, the maximum number of significant digits for the \fBg\fR
and \fBG\fR conversions; or the maximum number of bytes to be printed from a
string in \fBs\fR and \fBS\fR conversions. The precision takes the form of a
period (.) followed either by an asterisk (*), described below, or an optional
decimal digit string, where a null digit string is treated as 0. If a precision
appears with any other conversion specifier, the behavior is undefined.
.sp
If the conversion specifier is \fBs\fR or \fBS\fR, a standard-conforming
application (see \fBstandards\fR(7)) interprets the precision as the maximum
number of bytes to be written; an application that is not standard-conforming
interprets the precision as the maximum number of columns of screen display.
For an application that is not standard-conforming, \fB%.5s\fR would print only
the portion of the string that would display in 5 screen columns. Only complete
characters are written.
.sp
For \fB%ws\fR, the precision should be interpreted as the maximum number of
columns of screen display. The precision takes the form of a period (\fB\&.\fR)
followed by a decimal digit string; a null digit string is treated as zero.
Padding specified by the precision overrides the padding specified by the field
width.
.RE
.RS +4
.TP
.ie t \(bu
.el o
An optional \fIlength modifier\fR that specified the size of the argument.
.RE
.RS +4
.TP
.ie t \(bu
.el o
A \fIconversion specifier\fR that indicates the type of conversion to be
applied.
.RE
.sp
.LP
A field width, or precision, or both can be indicated by an asterisk
(\fB*\fR) . In this case, an argument of type \fBint\fR supplies the field width or
precision. Arguments specifying field width, or precision, or both must appear
in that order before the argument, if any, to be converted. A negative field
width is taken as a \(mi flag followed by a positive field width. A negative
precision is taken as if the precision were omitted. In format strings
containing the \fB%\fR\fIn\fR\fB$\fR form of a conversion specification, a
field width or precision may be indicated by the sequence
\fB*\fR\fIm\fR\fB$\fR, where \fIm\fR is a decimal integer in the range [1,
\fBNL_ARGMAX\fR] giving the position in the argument list (after the format
argument) of an integer argument containing the field width or precision, for
example:
.sp
.in +2
.nf
printf("%1$d:%2$.*3$d:%4$.*3$d\en", hour, min, precision, sec);
.fi
.in -2

.sp
.LP
The \fIformat\fR can contain either numbered argument specifications (that is,
\fB%\fR\fIn\fR\fB$\fR and \fB*\fR\fIm\fR\fB$\fR), or unnumbered argument
specifications (that is, \fB%\fR and \fB*\fR), but normally not both. The only
exception to this is that \fB%%\fR can be mixed with the \fB%\fR\fIn\fR\fB$\fR
form. The results of mixing numbered and unnumbered argument specifications in
a \fIformat\fR string are undefined. When numbered argument specifications are
used, specifying the \fIN\fRth argument requires that all the leading
arguments, from the first to the (\fIN-1\fR)th, are specified in the format
string.
.SS "Flag Characters"
The flag characters and their meanings are:
.sp
.ne 2
.na
\fB\fB\&'\fR\fR
.ad
.RS 9n
The integer portion of the result of a decimal conversion (\fB%i\fR, \fB%d\fR,
\fB%u\fR, \fB%f\fR, \fB%F\fR, \fB%g\fR, or \fB%G\fR) will be formatted with
thousands' grouping characters. For other conversions the behavior is
undefined. The non-monetary grouping character is used.
.RE

.sp
.ne 2
.na
\fB\fB\(mi\fR\fR
.ad
.RS 9n
The result of the conversion will be left-justified within the field. The
conversion will be right-justified if this flag is not specified.
.RE

.sp
.ne 2
.na
\fB\fB+\fR\fR
.ad
.RS 9n
The result of a signed conversion will always begin with a sign (+ or -). The
conversion will begin with a sign only when a negative value is converted if
this flag is not specified.
.RE

.sp
.ne 2
.na
\fB\fBspace\fR\fR
.ad
.RS 9n
If the first character of a signed conversion is not a sign or if a signed
conversion results in no characters, a space will be placed before the result.
This means that if the \fBspace\fR and \fB+\fR flags both appear, the space
flag will be ignored.
.RE

.sp
.ne 2
.na
\fB\fB#\fR\fR
.ad
.RS 9n
The value is to be converted to an alternate form. For \fBc\fR, \fBd\fR,
\fBi\fR, \fBs\fR, and \fBu\fR conversions, the flag has no effect. For an
\fBo\fR conversion, it increases the precision (if necessary) to force the
first digit of the result to be a zero. For \fBx\fR or \fBX\fR conversion, a
non-zero result will have \fB0x\fR (or \fB0X\fR) prepended to it. For \fBa\fR,
\fBA\fR, \fBe\fR, \fBE\fR, \fBf\fR, \fBF\fR, \fBg\fR, and \fBG\fR conversions,
the result will always contain a radix character, even if no digits follow the
radix character. Without this flag, the radix character appears in the result
of these conversions only if a digit follows it. For \fBg\fR and \fBG\fR
conversions, trailing zeros will not be removed from the result as they
normally are.
.RE

.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 9n
For \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, \fBX\fR, \fBa\fR, \fBA\fR,
\fBe\fR, \fBE\fR, \fBf\fR, \fBF\fR, \fBg\fR, and \fBG\fR conversions, leading
zeros (following any indication of sign or base) are used to pad to the field
width; no space padding is performed. If the \fB0\fR and \fB\(mi\fR flags both
appear, the \fB0\fR flag will be ignored. For \fBd\fR, \fBi\fR, \fBo\fR,
\fBu\fR, \fBx\fR, and \fBX\fR conversions, if a precision is specified, the
\fB0\fR flag will be ignored. If the \fB0\fR and \fB\&'\fR flags both appear,
the grouping characters are inserted before zero padding. For other
conversions, the behavior is undefined.
.RE

.SS "Length Modifiers"
The length modifiers and their meanings are:
.sp
.ne 2
.na
\fB\fBhh\fR\fR
.ad
.RS 16n
Specifies that a following \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, or
\fBX\fR conversion specifier applies to a \fBsigned char\fR or \fBunsigned
char\fR argument (the argument will have been promoted according to the integer
promotions, but its value will be converted to \fBsigned char\fR or \fBunsigned
char\fR before printing); or that a following \fBn\fR conversion specifier
applies to a pointer to a \fBsigned char\fR argument.
.RE

.sp
.ne 2
.na
\fB\fBh\fR\fR
.ad
.RS 16n
Specifies that a following \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, or
\fBX\fR conversion specifier applies to a \fBshort\fR or \fBunsigned short\fR
argument (the argument will have been promoted according to the integer
promotions, but its value will be converted to \fBshort\fR or \fBunsigned
short\fR before printing); or that a following \fBn\fR conversion specifier
applies to a pointer to a \fBshort\fR argument.
.RE

.sp
.ne 2
.na
\fB\fBl (ell)\fR\fR
.ad
.RS 16n
Specifies that a following \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, or
\fBX\fR conversion specifier applies to a \fBlong\fR or \fBunsigned long\fR
argument; that a following \fBn\fR conversion specifier applies to a pointer to
a \fBlong\fR argument; that a following \fBc\fR conversion specifier applies to
a \fBwint_t\fR argument; that a following \fBs\fR conversion specifier applies
to a pointer to a \fBwchar_t\fR argument; or has no effect on a following
\fBa\fR, \fBA\fR, \fBe\fR, \fBE\fR, \fBf\fR, \fBF\fR, \fBg\fR, or \fBG\fR
conversion specifier.
.RE

.sp
.ne 2
.na
\fB\fBll (ell-ell)\fR\fR
.ad
.RS 16n
Specifies that a following \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, or
\fBX\fR conversion specifier applies to a \fBlong long\fR or \fBunsigned long
long\fR argument; or that a following \fBn\fR conversion specifier applies to a
pointer to a \fBlong long\fR argument.
.RE

.sp
.ne 2
.na
\fB\fBj\fR\fR
.ad
.RS 16n
Specifies that a following \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, or
\fBX\fR conversion specifier applies to an \fBintmax_t\fR or \fBuintmax_t\fR
argument; or that a following \fBn\fR conversion specifier applies to a pointer
to an \fBintmax_t\fR argument. See NOTES.
.RE

.sp
.ne 2
.na
\fB\fBz\fR\fR
.ad
.RS 16n
Specifies that a following \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, or
\fBX\fR conversion specifier applies to a \fBsize_t\fR or the corresponding
signed integer type argument; or that a following \fBn\fR conversion specifier
applies to a pointer to a signed integer type corresponding to \fBsize_t\fR
argument.
.RE

.sp
.ne 2
.na
\fB\fBt\fR\fR
.ad
.RS 16n
Specifies that a following \fBd\fR, \fBi\fR, \fBo\fR, \fBu\fR, \fBx\fR, or
\fBX\fR conversion specifier applies to a \fBptrdiff_t\fR or the corresponding
unsigned type argument; or that a following n conversion specifier applies to a
pointer to a \fBptrdiff_t\fR argument.
.RE

.sp
.ne 2
.na
\fB\fBL\fR\fR
.ad
.RS 16n
Specifies that a following \fBa\fR, \fBA\fR, \fBe\fR, \fBE\fR, \fBf\fR,
\fBF\fR, \fBg\fR, or \fBG\fR conversion specifier applies to a \fBlong
double\fR argument.
.RE

.sp
.LP
If a length modifier appears with any conversion specifier other than as
specified above, the behavior is undefined.
.SS "Conversion Specifiers"
Each conversion specifier results in fetching zero or more arguments. The
results are undefined if there are insufficient arguments for the format. If
the format is exhausted while arguments remain, the excess arguments are
ignored.
.sp
.LP
The conversion specifiers and their meanings are:
.sp
.ne 2
.na
\fB\fBd\fR, \fBi\fR\fR
.ad
.RS 8n
The \fBint\fR argument is converted to a signed decimal in the style
\fB[\fR\(mi\fB]\fR\fIdddd\fR. The precision specifies the minimum number of
digits to appear; if the value being converted can be represented in fewer
digits, it will be expanded with leading zeros. The default precision is 1. The
result of converting 0 with an explicit precision of 0 is no characters.
.RE

.sp
.ne 2
.na
\fB\fBo\fR\fR
.ad
.RS 8n
The \fBunsigned int\fR argument is converted to unsigned octal format in the
style \fIdddd\fR. The precision specifies the minimum number of digits to
appear; if the value being converted can be represented in fewer digits, it
will be expanded with leading zeros. The default precision is 1. The result of
converting 0 with an explicit precision of 0 is no characters.
.RE

.sp
.ne 2
.na
\fB\fBu\fR\fR
.ad
.RS 8n
The \fBunsigned int\fR argument is converted to unsigned decimal format in the
style \fIdddd\fR. The precision specifies the minimum number of digits to
appear; if the value being converted can be represented in fewer digits, it
will be expanded with leading zeros. The default precision is 1. The result of
converting 0 with an explicit precision of 0 is no characters.
.RE

.sp
.ne 2
.na
\fB\fBx\fR\fR
.ad
.RS 8n
The \fBunsigned int\fR argument is converted to unsigned hexadecimal format in
the style \fIdddd\fR; the letters \fBabcdef\fR are used. The precision
specifies the minimum number of digits to appear; if the value being converted
can be represented in fewer digits, it will be expanded with leading zeros. The
default precision is 1. The result of converting 0 with an explicit precision
of 0 is no characters.
.RE

.sp
.ne 2
.na
\fB\fBX\fR\fR
.ad
.RS 8n
Behaves the same as the \fBx\fR conversion specifier except that letters
\fBABCDEF\fR are used instead of \fBabcdef\fR.
.RE

.sp
.ne 2
.na
\fB\fBf\fR, \fBF\fR\fR
.ad
.RS 8n
The \fBdouble\fR argument is converted to decimal notation in the style
[\fB\(mi\fR]\fIddd\fR\fB\&.\fR\fIddd\fR, where the number of digits after the
radix character (see \fBsetlocale\fR(3C)) is equal to the precision
specification. If the precision is missing it is taken as 6; if the precision
is explicitly 0 and the \fB#\fR flag is not specified, no radix character
appears. If a radix character appears, at least 1 digit appears before it. The
converted value is rounded to fit the specified output format according to the
prevailing floating point rounding direction mode. If the conversion is not
exact, an inexact exception is raised.
.sp
For the \fBf\fR specifier, a double argument representing an infinity or NaN is
converted in the style of the \fBe\fR conversion specifier, except that for an
infinite argument, "infinity" or "Infinity" is printed when the precision is at
least 8 and "inf" or "Inf" is printed otherwise.
.sp
For the F specifier, a double argument representing an infinity or NaN is
converted in the SUSv3 style of the E conversion specifier, except that for an
infinite argument, "INFINITY" is printed when the precision is at least 8 and
or "INF" is printed otherwise.
.RE

.sp
.ne 2
.na
\fB\fBe\fR, \fBE\fR\fR
.ad
.RS 8n
The \fBdouble\fR argument is converted to the style
[\fB\(mi\fR]\fId\fR\fB\&.\fR\fIddd\fR\fBe\fR\fI\(+-dd\fR, where there is one
digit before the radix character (which is non-zero if the argument is
non-zero) and the number of digits after it is equal to the precision. When the
precision is missing it is taken as 6; if the precision is 0 and the \fB#\fR
flag is not specified, no radix character appears. The \fBE\fR conversion
specifier will produce a number with \fBE\fR instead of \fBe\fR introducing the
exponent. The exponent always contains at least two digits. The converted value
is rounded to fit the specified output format according to the prevailing
floating point rounding direction mode. If the conversion is not exact, an
inexact exception is raised.
.sp
Infinity and NaN values are handled in one of the following ways:
.sp
.ne 2
.na
\fBSUSv3\fR
.ad
.RS 11n
For the \fBe\fR specifier, a \fBdouble\fR argument representing an infinity is
printed as "[\(mi]\fBinfinity\fR", when the precision for the conversion is at
least 7 and as "[\(mi]\fBinf\fR" otherwise. A \fBdouble\fR argument
representing a NaN is printed as "[\(mi]\fBnan\fR". For the \fBE\fR specifier,
"\fBINF\fR", "\fBINFINITY\fR", and "\fBNAN\fR" are printed instead of
"\fBinf\fR", "\fBinfinity\fR", and "\fBnan\fR", respectively. Printing of the
sign follows the rules described above.
.RE

.sp
.ne 2
.na
\fBDefault\fR
.ad
.RS 11n
A \fBdouble\fR argument representing an infinity is printed as
"[\(mi]\fBInfinity\fR", when the precision for the conversion is at least 7 and
as "[\(mi]\fBInf\fR" otherwise. A double argument representing a NaN is printed
as "[\(mi]\fBNaN\fR". Printing of the sign follows the rules described above.
.RE

.RE

.sp
.ne 2
.na
\fB\fBg\fR, \fBG\fR\fR
.ad
.RS 8n
The \fBdouble\fR argument is printed in style \fBf\fR or \fBe\fR (or in style
\fBE\fR in the case of a \fBG\fR conversion specifier), with the precision
specifying the number of significant digits. If an explicit precision is 0, it
is taken as 1. The style used depends on the value converted: style \fBe\fR (or
\fBE\fR) will be used only if the exponent resulting from the conversion is
less than -4 or greater than or equal to the precision. Trailing zeros are
removed from the fractional part of the result. A radix character appears only
if it is followed by a digit.
.sp
A \fBdouble\fR argument representing an infinity or NaN is converted in the
style of the \fBe\fR or \fBE\fR conversion specifier, except that for an
infinite argument, "infinity", "INFINITY", or "Infinity" is printed when the
precision is at least 8 and "inf", "INF", or "Inf" is printed otherwise.
.RE

.sp
.ne 2
.na
\fB\fBa\fR, \fBA\fR\fR
.ad
.RS 8n
A \fBdouble\fR argument representing a floating-point number is converted in
the style "[-]0\fIxh\fR.\fIhhhhp\fR\(+-\fId\fR", where the single hexadecimal
digit preceding the radix point is 0 if the value converted is zero and 1
otherwise and the number of hexadecimal digits after it is equal to the
precision; if the precision is missing, the number of digits printed after the
radix point is 13 for the conversion of a double value, 16 for the conversion
of a long double value on x86, and 28 for the conversion of a long double value
on SPARC; if the precision is zero and the '#' flag is not specified, no
decimal-point character will appear. The letters "\fBabcdef\fR" are used for
\fBa\fR conversion and the letters "\fBABCDEF\fR" for \fBA\fR conversion. The
\fBA\fR conversion specifier produces a number with '\fBX\fR' and '\fBP\fR'
instead of '\fBx\fR' and '\fBp\fR'. The exponent will always contain at least
one digit, and only as many more digits as necessary to represent the decimal
exponent of 2. If the value is zero, the exponent is zero.
.sp
The converted value is rounded to fit the specified output format according to
the prevailing floating point rounding direction mode. If the conversion is not
exact, an inexact exception is raised.
.sp
A \fBdouble\fR argument representing an infinity or NaN is converted in the
SUSv3 style of an \fBe\fR or \fBE\fR conversion specifier.
.RE

.sp
.ne 2
.na
\fB\fBc\fR\fR
.ad
.RS 8n
The \fBint\fR argument is converted to an \fBunsigned char\fR, and the
resulting byte is printed.
.sp
If an \fBl\fR (ell) qualifier is present, the \fBwint_t\fR argument is
converted as if by an \fBls\fR conversion specification with no precision and
an argument that points to a two-element array of type \fBwchar_t\fR, the first
element of which contains the \fBwint_t\fR argument to the \fBls\fR conversion
specification and the second element contains a null wide-character.
.RE

.sp
.ne 2
.na
\fB\fBC\fR\fR
.ad
.RS 8n
Same as \fBlc\fR.
.RE

.sp
.ne 2
.na
\fB\fBwc\fR\fR
.ad
.RS 8n
The \fBint\fR argument is converted to a wide character (\fBwchar_t\fR), and
the resulting wide character is printed.
.RE

.sp
.ne 2
.na
\fB\fBs\fR\fR
.ad
.RS 8n
The argument must be a pointer to an array of \fBchar\fR. Bytes from the array
are written up to (but not including) any terminating null byte. If a precision
is specified, a standard-conforming application (see \fBstandards\fR(7)) will
write only the number of bytes specified by precision; an application that is
not standard-conforming will write only the portion of the string that will
display in the number of columns of screen display specified by precision. If
the precision is not specified, it is taken to be infinite, so all bytes up to
the first null byte are printed. An argument with a null value will print
.BR (null) .
Note, while this behavior is common across many operating systems, POSIX does
not guarantee this behavior and portable applications should avoid passing
NULL.
.sp
If an \fBl\fR (ell) qualifier is present, the argument must be a pointer to an
array of type \fBwchar_t\fR. Wide-characters from the array are converted to
characters (each as if by a call to the \fBwcrtomb\fR(3C) function, with the
conversion state described by an \fBmbstate_t\fR object initialized to zero
before the first wide-character is converted) up to and including a terminating
null wide-character. The resulting characters are written up to (but not
including) the terminating null character (byte). If no precision is specified,
the array must contain a null wide-character. If a precision is specified, no
more than that many characters (bytes) are written (including shift sequences,
if any), and the array must contain a null wide-character if, to equal the
character sequence length given by the precision, the function would need to
access a wide-character one past the end of the array. In no case is a partial
character written.
.RE

.sp
.ne 2
.na
\fB\fBS\fR\fR
.ad
.RS 8n
Same as \fBls\fR.
.RE

.sp
.ne 2
.na
\fB\fBws\fR\fR
.ad
.RS 8n
The argument must be a pointer to an array of \fBwchar_t\fR. Bytes from the
array are written up to (but not including) any terminating null character. If
the precision is specified, only that portion of the wide-character array that
will display in the number of columns of screen display specified by precision
will be written. If the precision is not specified, it is taken to be infinite,
so all wide characters up to the first null character are printed. An argument
with a null value will print
.BR (null) .
.RE

.sp
.ne 2
.na
\fB\fBp\fR\fR
.ad
.RS 8n
The argument must be a pointer to \fBvoid\fR. The value of the pointer is
converted to a set of sequences of printable characters, which should be the
same as the set of sequences that are matched by the \fB%p\fR conversion of the
\fBscanf\fR(3C) function.
.RE

.sp
.ne 2
.na
\fB\fBn\fR\fR
.ad
.RS 8n
The argument must be a pointer to an integer into which is written the number
of bytes written to the output standard I/O stream so far by this call to one
of the \fBprintf()\fR functions. No argument is converted.
.RE

.sp
.ne 2
.na
\fB\fB%\fR\fR
.ad
.RS 8n
Print a \fB%\fR; no argument is converted. The entire conversion specification
must be %%.
.RE

.sp
.LP
If a conversion specification does not match one of the above forms, the
behavior is undefined.
.sp
.LP
In no case does a non-existent or small 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. Characters generated by
\fBprintf()\fR and \fBfprintf()\fR are printed as if the \fBputc\fR(3C)
function had been called.
.sp
.LP
The \fBst_ctime\fR and \fBst_mtime\fR fields of the file will be marked for
update between the call to a successful execution of \fBprintf()\fR or
\fBfprintf()\fR and the next successful completion of a call to
\fBfflush\fR(3C) or \fBfclose\fR(3C) on the same stream or a call to
\fBexit\fR(3C) or \fBabort\fR(3C).
.SH RETURN VALUES
The \fBprintf()\fR, \fBfprintf()\fR, \fBsprintf()\fR, and \fBasprintf()\fR
functions return the number of bytes transmitted (excluding the terminating
null byte in the case of \fBsprintf()\fR and \fBasprintf()\fR).
.sp
.LP
The \fBsnprintf()\fR function returns the number of bytes that would have been
written to \fIs\fR if \fIn\fR had been sufficiently large (excluding the
terminating null byte.) If the value of \fIn\fR is 0 on a call to
\fBsnprintf()\fR, \fIs\fR can be a null pointer and the number of bytes that
would have been written if \fIn\fR had been sufficiently large (excluding the
terminating null byte) is returned.
.sp
.LP
Each function returns a negative value if an output error was encountered.
.SH ERRORS
For the conditions under which \fBprintf()\fR and \fBfprintf()\fR will fail and
may fail, refer to \fBfputc\fR(3C) or \fBfputwc\fR(3C).
.sp
.LP
The \fBsnprintf()\fR function will fail if:
.sp
.ne 2
.na
\fB\fBEOVERFLOW\fR\fR
.ad
.RS 13n
The value of \fIn\fR is greater than \fBINT_MAX\fR or the number of bytes
needed to hold the output excluding the terminating null is greater than
\fBINT_MAX\fR.
.RE

.sp
.LP
The \fBprintf()\fR, \fBfprintf()\fR, \fBsprintf()\fR, and \fBsnprintf()\fR
functions may fail if:
.sp
.ne 2
.na
\fB\fBEILSEQ\fR\fR
.ad
.RS 10n
A wide-character code that does not correspond to a valid character has been
detected.
.RE

.sp
.ne 2
.na
\fB\fBEINVAL\fR\fR
.ad
.RS 10n
There are insufficient arguments.
.RE

.sp
.LP
The \fBprintf()\fR, \fBfprintf()\fR, and \fBasprintf()\fR functions may fail
due to an underlying \fBmalloc\fR(3C) failure if:
.sp
.ne 2
.na
\fB\fBEAGAIN\fR\fR
.ad
.RS 10n
Storage space is temporarily unavailable.
.RE

.sp
.ne 2
.na
\fB\fBENOMEM\fR\fR
.ad
.RS 10n
Insufficient storage space is available.
.RE

.SH USAGE
If the application calling the \fBprintf()\fR functions has any objects of type
\fBwint_t\fR or \fBwchar_t\fR, it must also include the header \fB<wchar.h>\fR
to have these objects defined.
.SS "Escape Character Sequences"
It is common to use the following escape sequences built into the C language
when entering format strings for the \fBprintf()\fR functions, but these
sequences are processed by the C compiler, not by the \fBprintf()\fR function.
.sp
.ne 2
.na
\fB\fB\ea\fR\fR
.ad
.RS 7n
Alert. Ring the bell.
.RE

.sp
.ne 2
.na
\fB\fB\eb\fR\fR
.ad
.RS 7n
Backspace. Move the printing position to one character before the current
position, unless the current position is the start of a line.
.RE

.sp
.ne 2
.na
\fB\fB\ef\fR\fR
.ad
.RS 7n
Form feed. Move the printing position to the initial printing position of the
next logical page.
.RE

.sp
.ne 2
.na
\fB\fB\en\fR\fR
.ad
.RS 7n
Newline. Move the printing position to the start of the next line.
.RE

.sp
.ne 2
.na
\fB\fB\er\fR\fR
.ad
.RS 7n
Carriage return. Move the printing position to the start of the current line.
.RE

.sp
.ne 2
.na
\fB\fB\et\fR\fR
.ad
.RS 7n
Horizontal tab. Move the printing position to the next implementation-defined
horizontal tab position on the current line.
.RE

.sp
.ne 2
.na
\fB\fB\ev\fR\fR
.ad
.RS 7n
Vertical tab. Move the printing position to the start of the next
implementation-defined vertical tab position.
.RE

.sp
.LP
In addition, the C language supports character sequences of the form
.sp
.LP
\eoctal-number
.sp
.LP
and
.sp
.LP
\ehex-number
.sp
.LP
which translates into the character represented by the octal or hexadecimal
number. For example, if ASCII representations are being used, the letter 'a'
may be written as '\e141' and 'Z' as '\e132'. This syntax is most frequently
used to represent the null character as '\e0'. This is exactly equivalent to
the numeric constant zero (0). Note that the octal number does not include the
zero prefix as it would for a normal octal constant. To specify a hexadecimal
number, omit the zero so that the prefix is an 'x' (uppercase 'X' is not
allowed in this context). Support for hexadecimal sequences is an ANSI
extension. See \fBstandards\fR(7).
.SH EXAMPLES
\fBExample 1 \fRTo print the language-independent date and time format, the
following statement could be used:
.sp
.in +2
.nf
\fBprintf (format, weekday, month, day, hour, min);\fR
.fi
.in -2

.sp
.LP
For American usage, \fIformat\fR could be a pointer to the string:

.sp
.in +2
.nf
\fB"%s, %s %d, %d:%.2d\en"\fR
.fi
.in -2

.sp
.LP
producing the message:

.sp
.in +2
.nf
\fBSunday, July 3, 10:02\fR
.fi
.in -2

.sp
.LP
whereas for German usage, \fIformat\fR could be a pointer to the string:

.sp
.in +2
.nf
"%1$s, %3$d. %2$s, %4$d:%5$.2d\en"
.fi
.in -2

.sp
.LP
producing the message:

.sp
.in +2
.nf
Sonntag, 3. Juli, 10:02
.fi
.in -2

.LP
\fBExample 2 \fRTo print a date and time in the form \fBSunday, July 3,
10:02\fR, where \fBweekday\fR and \fBmonth\fR are pointers to null-terminated
strings:
.sp
.in +2
.nf
printf("%s, %s %i, %d:%.2d", weekday, month, day, hour, min);
.fi
.in -2

.LP
\fBExample 3 \fRTo print pi to 5 decimal places:
.sp
.in +2
.nf
printf("pi = %.5f", 4 * atan(1.0));
.fi
.in -2

.SS "Default"
\fBExample 4 \fRThe following example applies only to applications that are not
standard-conforming. To print a list of names in columns which are 20
characters wide:
.sp
.in +2
.nf
\fBprintf("%20s%20s%20s", lastname, firstname, middlename);\fR
.fi
.in -2

.SH ATTRIBUTES
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
l | l
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	Enabled
_
Interface Stability	Committed
_
MT-Level	See below.
_
Standard	See below.
.TE

.sp
.LP
All of these functions can be used safely in multithreaded applications, as
long as \fBsetlocale\fR(3C) is not being called to change the locale. The
\fBsprintf()\fR and \fBsnprintf()\fR functions are Async-Signal-Safe.
.sp
.LP
See \fBstandards\fR(7) for the standards conformance of \fBprintf()\fR,
\fBfprintf()\fR, \fBsprintf()\fR, and \fBsnprintf()\fR. The \fBasprintf()\fR
function is modeled on the one that appears in the FreeBSD, NetBSD, and GNU C
libraries.
.SH SEE ALSO
.BR exit (2),
.BR lseek (2),
.BR write (2),
.BR abort (3C),
.BR ecvt (3C),
.BR exit (3C),
.BR fclose (3C),
.BR fflush (3C),
.BR fputwc (3C),
.BR free (3C),
.BR malloc (3C),
.BR putc (3C),
.BR scanf (3C),
.BR setlocale (3C),
.BR stdio (3C),
.BR vprintf (3C),
.BR wcstombs (3C),
.BR wctomb (3C),
.BR attributes (7),
.BR environ (7),
.BR standards (7)
.SH NOTES
If the \fBj\fR length modifier is used, 32-bit applications that were compiled
using \fBc89\fR on releases prior to Solaris 10 will experience undefined
behavior.
.sp
.LP
The \fBsnprintf()\fR return value when \fIn\fR = 0 was changed in the Solaris
10 release. The change was based on the SUSv3 specification. The previous
behavior was based on the initial SUSv2 specification, where \fBsnprintf()\fR
when \fIn\fR = 0 returns an unspecified value less than 1.