path: root/usr/src/man/man1/printf.1

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.TH PRINTF 1 "May 11, 2014"
.SH NAME
printf \- write formatted output
.SH SYNOPSIS
.SS "/usr/bin/printf"
.LP
.nf
\fBprintf\fR \fIformat\fR [\fIargument\fR]...
.fi

.SS "ksh93"
.LP
.nf
\fBprintf\fR \fIformat\fR [\fIstring\fR...]
.fi

.SH DESCRIPTION
.SS "/usr/bin/printf"
.sp
.LP
The \fBprintf\fR utility writes each string operand to standard output using
\fIformat\fR to control the output format.
.SH OPERANDS
.SS "/usr/bin/printf"
.sp
.LP
The following operands are supported by \fB/usr/bin/printf\fR:
.sp
.ne 2
.na
\fB\fIformat\fR\fR
.ad
.RS 12n
A string describing the format to use to write the remaining operands. The
\fIformat\fR operand is used as the \fIformat\fR string described on the
\fBformats\fR(5) manual page, with the following exceptions:
.RS +4
.TP
.ie t \(bu
.el o
A \fBSPACE\fR character in the format string, in any context other than a flag
of a conversion specification, is treated as an ordinary character that is
copied to the output.
.RE
.RS +4
.TP
.ie t \(bu
.el o
A character in the format string is treated as a character, not as a
\fBSPACE\fR character.
.RE
.RS +4
.TP
.ie t \(bu
.el o
In addition to the escape sequences described on the \fBformats\fR(5) manual
page (\fB\e\e\fR, \fB\ea\fR, \fB\eb\fR, \fB\ef\fR, \fB\en\fR, \fB\er\fR,
\fB\et\fR, \fB\ev\fR), \fB\e\fR\fIddd\fR, where \fIddd\fR is a one-, two- or
three-digit octal number, is written as a byte with the numeric value specified
by the octal number.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The program does not precede or follow output from the \fBd\fR or \fBu\fR
conversion specifications with blank characters not specified by the
\fIformat\fR operand.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The program does not precede output from the \fBo\fR conversion specification
with zeros not specified by the \fIformat\fR operand.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The argument used for the conversion character (or width or precision
parameters, see below) may be taken from the \fIn\fRnth argument instead
of the next unused argument, by specifying \fIn\fR\fB$\fR immediately following
the \fB%\fR character, or the \fB*\fR character (for width or precision
arguments).
If \fIn\fR\fB$\fR appears in any conversions in the format string,
then it must be used for all conversions, including any variable width or
precision specifiers.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The special character \fB*\fR may be used instead of a string of decimal digits
to indicate a minimum field width or a precision.  In this case the next
available argument is used (or the \fIn\fRth if the form \fIn\fR\fB$\fR is
used), treating its value as a decimal string.
.RE
.RS +4
.TP
.ie t \(bu
.el o
An additional conversion character, \fBb\fR, is supported as follows. The
argument is taken to be a string that can contain backslash-escape sequences.
The following backslash-escape sequences are supported:
.RS +4
.TP
.ie t \(bu
.el o
the escape sequences listed on the \fBformats\fR(5) manual page (\fB\e\e\fR,
\fB\ea\fR, \fB\eb\fR, \fB\ef\fR, \fB\en\fR, \fB\er\fR, \fB\et\fR, \fB\ev\fR),
which are converted to the characters they represent
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fB\e0\fR\fIddd\fR, where \fIddd\fR is a zero-, one-, two- or three-digit octal
number that is converted to a byte with the numeric value specified by the
octal number
.RE
.RS +4
.TP
.ie t \(bu
.el o
\fB\ec\fR, which is written and causes \fBprintf\fR to ignore any remaining
characters in the string operand containing it, any remaining string operands
and any additional characters in the \fIformat\fR operand.
.RE
.RE
The interpretation of a backslash followed by any other sequence of characters
is unspecified.
.sp
Bytes from the converted string are written until the end of the string or the
number of bytes indicated by the precision specification is reached. If the
precision is omitted, it is taken to be infinite, so all bytes up to the end of
the converted string are written. For each specification that consumes an
argument, the next argument operand is evaluated and converted to the
appropriate type for the conversion as specified below. The \fIformat\fR
operand is reused as often as necessary to satisfy the argument operands. Any
extra \fBc\fR or \fBs\fR conversion specifications are evaluated as if a null
string argument were supplied; other extra conversion specifications are
evaluated as if a zero argument were supplied.
.sp
When there are more argument operands than format specifiers, and the
format includes \fIn\fR\fB$\fR position indicators, then the format is
reprocessed from the beginning as above, but with the argument list starting
from the next argument after the highest \fIn\fRth argument previously
encountered.
.sp
If the \fIformat\fR operand
contains no conversion specifications and \fIargument\fR operands are present,
the results are unspecified. If a character sequence in the \fIformat\fR
operand begins with a \fB%\fR character, but does not form a valid conversion
specification, the behavior is unspecified.
.RE

.sp
.ne 2
.na
\fB\fIargument\fR\fR
.ad
.RS 12n
The strings to be written to standard output, under the control of
\fBformat\fR. The \fIargument\fR operands are treated as strings if the
corresponding conversion character is \fBb\fR, \fBc\fR or \fBs\fR. Otherwise,
it is evaluated as a C constant, as described by the ISO C standard, with the
following extensions:
.RS +4
.TP
.ie t \(bu
.el o
A leading plus or minus sign is allowed.
.RE
.RS +4
.TP
.ie t \(bu
.el o
If the leading character is a single- or double-quote, the value is the numeric
value in the underlying codeset of the character following the single- or
double-quote.
.RE
If an argument operand cannot be completely converted into an internal value
appropriate to the corresponding conversion specification, a diagnostic message
is written to standard error and the utility does not exit with a zero exit
status, but continues processing any remaining operands and writes the value
accumulated at the time the error was detected to standard output.
.RE

.SS "ksh93"
.sp
.LP
The \fIformat\fR operands support the full range of ANSI C/C99/XPG6 formatting
specifiers as well as additional specifiers:
.sp
.ne 2
.na
\fB\fB%b\fR\fR
.ad
.RS 6n
Each character in the string operand is processed specially, as follows:
.sp
.ne 2
.na
\fB\fB\ea\fR\fR
.ad
.RS 8n
Alert character.
.RE

.sp
.ne 2
.na
\fB\fB\eb\fR\fR
.ad
.RS 8n
Backspace character.
.RE

.sp
.ne 2
.na
\fB\fB\ec\fR\fR
.ad
.RS 8n
Terminate output without appending NEWLINE. The remaining string operands are
ignored.
.RE

.sp
.ne 2
.na
\fB\fB\eE\fR\fR
.ad
.RS 8n
Escape character (\fBASCII\fR octal \fB033\fR).
.RE

.sp
.ne 2
.na
\fB\fB\ef\fR\fR
.ad
.RS 8n
FORM FEED character.
.RE

.sp
.ne 2
.na
\fB\fB\en\fR\fR
.ad
.RS 8n
NEWLINE character.
.RE

.sp
.ne 2
.na
\fB\fB\et\fR\fR
.ad
.RS 8n
TAB character.
.RE

.sp
.ne 2
.na
\fB\fB\ev\fR\fR
.ad
.RS 8n
Vertical tab character.
.RE

.sp
.ne 2
.na
\fB\fB\e\e\fR\fR
.ad
.RS 8n
Backslash character.
.RE

.sp
.ne 2
.na
\fB\fB\e0\fR\fIx\fR\fR
.ad
.RS 8n
The 8-bit character whose \fBASCII\fR code is the \fB1\fR-, \fB2\fR-, or
\fB3\fR-digit octal number \fIx\fR.
.RE

.RE

.sp
.ne 2
.na
\fB\fB%B\fR\fR
.ad
.RS 6n
Treat the argument as a variable name and output the value without converting
it to a string. This is most useful for variables of type \fB-b\fR.
.RE

.sp
.ne 2
.na
\fB\fB%H\fR\fR
.ad
.RS 6n
Output string with characters \fB<\fR, \fB&\fR, \fB>\fR, \fB"\fR, and
non-printable characters, properly escaped for use in HTML and XML documents.
.RE

.sp
.ne 2
.na
\fB\fB%P\fR\fR
.ad
.RS 6n
Treat \fIstring\fR as an extended regular expression and convert it to a shell
pattern.
.RE

.sp
.ne 2
.na
\fB\fB%q\fR\fR
.ad
.RS 6n
Output \fIstring\fR quoted in a manner that it can be read in by the shell to
get back the same string. However, empty strings resulting from missing string
operands are not quoted.
.RE

.sp
.ne 2
.na
\fB\fB%R\fR\fR
.ad
.RS 6n
Treat \fIstring\fR as an shell pattern expression and convert it to an extended
regular expression.
.RE

.sp
.ne 2
.na
\fB\fB%T\fR\fR
.ad
.RS 6n
Treat \fIstring\fR as a date/time string and format it. The \fBT\fR can be
preceded by (\fIdformat\fR), where \fIdformat\fR is a date format as defined by
the \fBdate\fR(1) command.
.RE

.sp
.ne 2
.na
\fB\fB%Z\fR\fR
.ad
.RS 6n
Output a byte whose value is \fB0\fR.
.RE

.sp
.LP
When performing conversions of \fIstring\fR to satisfy a numeric format
specifier, if the first character of \fIstring\fR is \fB"or'\fR, the value is
the numeric value in the underlying code set of the character following the
\fB"or'\fR. Otherwise, \fIstring\fR is treated like a shell arithmetic
expression and evaluated.
.sp
.LP
If a \fIstring\fR operand cannot be completely converted into a value
appropriate for that format specifier, an error occurs, but remaining
\fIstring\fR operands continue to be processed.
.sp
.LP
In addition to the format specifier extensions, the following extensions of
ANSI C/C99/XPG6 are permitted in format specifiers:
.RS +4
.TP
.ie t \(bu
.el o
The escape sequences \fB\eE\fR and \fB\ee\fR expand to the escape character
which is octal 033 in ASCII.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The escape sequence \fB\ecx\fR expands to CTRL-x.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The escape sequence \fB\eC[.\fR\fIname\fR\fB\&.]\fR expands to the collating
element \fIname\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The escape sequence \fB\ex{hex}\fR expands to the character corresponding to
the hexadecimal value \fBhex\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The format modifier flag = can be used to center a field to a specified width.
When the output is a terminal, the character width is used rather than the
number of bytes.
.RE
.RS +4
.TP
.ie t \(bu
.el o
Each of the integral format specifiers can have a third modifier after width
and precision that specifies the base of the conversion from 2 to 64. In this
case, the \fB#\fR modifier causes \fIbase\fR\fB#\fR to be prepended to the
value.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The \fB#\fR modifier can be used with the \fBd\fR specifier when no base is
specified to cause the output to be written in units of 1000 with a suffix of
one of \fBk M G T P E\fR.
.RE
.RS +4
.TP
.ie t \(bu
.el o
The \fB#\fR modifier can be used with the \fBi\fR specifier to cause the output
to be written in units of \fB1024\fR with a suffix of one of \fBKi Mi Gi Ti Pi
Ei\fR.
.RE
.sp
.LP
If there are more \fIstring\fR operands than format specifiers, the format
string is reprocessed from the beginning. If there are fewer \fIstring\fR
operands than format specifiers, then \fIstring\fR specifiers are treated as if
empty strings were supplied, numeric conversions are treated as if \fB0\fR was
supplied, and time conversions are treated as if \fBnow\fR was supplied.
.sp
.LP
When there are more argument operands than format specifiers, and the
format includes \fIn\fR\fB$\fR position indicators, then the format is
reprocessed from the beginning as above, but with the argument list starting
from the next argument after the highest \fIn\fRth argument previously
encountered.
.sp
.LP
\fB/usr/bin/printf\fR is equivalent to \fBksh93\fR's \fBprintf\fR built-in and
\fBprint -f\fR, which allows additional options to be specified.
.SH USAGE
.SS "/usr/bin/printf"
.sp
.LP
The \fBprintf\fR utility, like the \fBprintf\fR(3C) function on which it is
based, makes no special provision for dealing with multi-byte characters when
using the \fB%c\fR conversion specification. Applications should be extremely
cautious using either of these features when there are multi-byte characters in
the character set.
.sp
.LP
The \fB%b\fR conversion specification is not part of the ISO C standard; it has
been added here as a portable way to process backslash escapes expanded in
string operands as provided by the \fBecho\fR utility. See also the USAGE
section of the \fBecho\fR(1) manual page for ways to use \fBprintf\fR as a
replacement for all of the traditional versions of the \fBecho\fR utility.
.sp
.LP
If an argument cannot be parsed correctly for the corresponding conversion
specification, the \fBprintf\fR utility reports an error. Thus, overflow and
extraneous characters at the end of an argument being used for a numeric
conversion are to be reported as errors.
.sp
.LP
It is not considered an error if an argument operand is not completely used for
a \fBc\fR or \fBs\fR conversion or if a string operand's first or second
character is used to get the numeric value of a character.
.SH EXAMPLES
.SS "/usr/bin/printf"
.LP
\fBExample 1 \fRPrinting a Series of Prompts
.sp
.LP
The following example alerts the user, then prints and reads a series of
prompts:

.sp
.in +2
.nf
example% \fBprintf "\eaPlease fill in the following: \enName: "
read name
printf "Phone number: "
read phone\fR
.fi
.in -2
.sp

.LP
\fBExample 2 \fRPrinting a Table of Calculations
.sp
.LP
The following example prints a table of calculations. It reads out a list of
right and wrong answers from a file, calculates the percentage correctly, and
prints them out. The numbers are right-justified and separated by a single tab
character. The percentage is written to one decimal place of accuracy:

.sp
.in +2
.nf
example% \fBwhile read right wrong ; do
   percent=$(echo "scale=1;($right*100)/($right+$wrong)" | bc)
   printf "%2d right\et%2d wrong\et(%s%%)\en" \e
	   $right $wrong $percent
done < database_file\fR
.fi
.in -2
.sp

.LP
\fBExample 3 \fRPrinting number strings
.sp
.LP
The command:

.sp
.in +2
.nf
example% \fBprintf "%5d%4d\en" 1 21 321 4321 54321\fR
.fi
.in -2
.sp

.sp
.LP
produces:

.sp
.in +2
.nf
    1  21
  3214321
54321   0
.fi
.in -2
.sp

.sp
.LP
The \fIformat\fR operand is used three times to print all of the given strings
and that a \fB0\fR was supplied by \fBprintf\fR to satisfy the last \fB%4d\fR
conversion specification.

.LP
\fBExample 4 \fRTabulating Conversion Errors
.sp
.LP
The following example tabulates conversion errors.

.sp
.LP
The \fBprintf\fR utility tells the user when conversion errors are detected
while producing numeric output. These results would be expected on an
implementation with 32-bit twos-complement integers when \fB%d\fR is specified
as the \fIformat\fR operand:

.sp

.sp
.TS
box;
c c c
l l l .
Arguments	Standard	Diagnostic
5a	5	printf: 5a not completely converted
9999999999	2147483647	printf: 9999999999: Results too large
-9999999999	-2147483648	printf: -9999999999: Results too large
ABC	0	printf: ABC expected numeric value
.TE

.sp
.LP
The value shown on standard output is what would be expected as the return
value from the function \fBstrtol\fR(3C). A similar correspondence exists
between \fB%u\fR and \fBstrtoul\fR(3C), and \fB%e\fR, \fB%f\fR and \fB%g\fR and
\fBstrtod\fR(3C).

.LP
\fBExample 5 \fRPrinting Output for a Specific Locale
.sp
.LP
The following example prints output for a specific locale. In a locale using
the ISO/IEC 646:1991 standard as the underlying codeset, the command:

.sp
.in +2
.nf
example% \fBprintf "%d\en" 3 +3 -3 \e'3 \e"+3 "'-3"\fR
.fi
.in -2
.sp

.sp
.LP
produces:

.sp

.sp
.TS
box;
l l
l l .
\fB3\fR	Numeric value of constant 3
\fB3\fR	Numeric value of constant 3
\fB\(mi3\fR	Numeric value of constant \(mi3
\fB51\fR	T{
Numeric value of the character `3' in the ISO/IEC 646:1991 standard codeset
T}
\fB43\fR	T{
Numeric value of the character `+' in the ISO/IEC 646:1991 standard codeset
T}
\fB45\fR	T{
Numeric value of the character `\(mi' in the SO/IEC 646:1991 standard codeset
T}
.TE

.sp
.LP
In a locale with multi-byte characters, the value of a character is intended to
be the value of the equivalent of the \fBwchar_t\fR representation of the
character.

.sp
.LP
If an argument operand cannot be completely converted into an internal value
appropriate to the corresponding conversion specification, a diagnostic message
is written to standard error and the utility does exit with a zero exit status,
but continues processing any remaining operands and writes the value
accumulated at the time the error was detected to standard output.

.LP
\fBExample 6 \fRAlternative floating point representation 1
.sp
.LP
The \fBprintf\fR utility supports an alternative floating point representation
(see \fBprintf\fR(3C) entry for the "\fB%a\fR"/"\fB%A\fR"), which allows the
output of floating-point values in a format that avoids the usual base16 to
base10 rounding errors.

.sp
.in +2
.nf
example% printf "%a\en" 2 3.1 NaN
.fi
.in -2
.sp

.sp
.LP
produces:

.sp
.in +2
.nf
0x1.0000000000000000000000000000p+01
0x1.8ccccccccccccccccccccccccccdp+01
nan
.fi
.in -2
.sp

.LP
\fBExample 7 \fRAlternative floating point representation 2
.sp
.LP
The following example shows two different representations of the same
floating-point value.

.sp
.in +2
.nf
example% x=2 ; printf "%f == %a\en" x x
.fi
.in -2
.sp

.sp
.LP
produces:

.sp
.in +2
.nf
2.000000 == 0x1.0000000000000000000000000000p+01
.fi
.in -2
.sp

.LP
\fBExample 8 \fROutput of unicode values
.sp
.LP
The following command will print the EURO unicode symbol (code-point 0x20ac).

.sp
.in +2
.nf
example% LC_ALL=en_US.UTF-8 printf "\u[20ac]\en"
.fi
.in -2
.sp

.sp
.LP
produces:

.sp
.in +2
.nf
<euro>
.fi
.in -2
.sp

.sp
.LP
where "<euro>" represents the EURO currency symbol character.

.LP
\fBExample 9 \fRConvert unicode character to unicode code-point value
.sp
.LP
The following command will print the hexadecimal value of a given character.

.sp
.in +2
.nf
example% export LC_ALL=en_US.UTF-8
example% printf "%x\en" "'<euro>"
.fi
.in -2
.sp

.sp
.LP
where "<euro>" represents the EURO currency symbol character (code-point
0x20ac).

.sp
.LP
produces:

.sp
.in +2
.nf
20ac
.fi
.in -2
.sp

.LP
\fBExample 10 \fRPrint the numeric value of an ASCII character
.sp
.in +2
.nf
example% printf "%d\en" "'A"
.fi
.in -2
.sp

.sp
.LP
produces:

.sp
.in +2
.nf
65
.fi
.in -2
.sp

.LP
\fBExample 11 \fRPrint the language-independent date and time format
.sp
.LP
To print the language-independent date and time format, the following statement
could be used:

.sp
.in +2
.nf
example% printf "format" weekday month day hour min
.fi
.in -2
.sp

.sp
.LP
For example,

.sp
.in +2
.nf
$ printf format "Sunday" "July" 3 10 2
.fi
.in -2
.sp

.sp
.LP
For American usage, format could be the string:

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

.sp
.LP
producing the message:

.sp
.in +2
.nf
Sunday, July 3, 10:02
.fi
.in -2
.sp

.sp
.LP
Whereas for EU usage, format could be the string:

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

.sp
.LP
Note that the '$' characters must be properly escaped, such as

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

.sp
.LP
producing the message:

.sp
.in +2
.nf
Sunday, 3. July, 10:02
.fi
.in -2
.sp

.SH ENVIRONMENT VARIABLES
.sp
.LP
See \fBenviron\fR(5) for descriptions of the following environment variables
that affect the execution of \fBprintf\fR: \fBLANG\fR, \fBLC_ALL\fR,
\fBLC_CTYPE\fR, \fBLC_MESSAGES\fR, \fBLC_NUMERIC\fR, and \fBNLSPATH\fR.
.SH EXIT STATUS
.sp
.LP
The following exit values are returned:
.sp
.ne 2
.na
\fB\fB0\fR\fR
.ad
.RS 6n
Successful completion.
.RE

.sp
.ne 2
.na
\fB\fB>0\fR\fR
.ad
.RS 6n
An error occurred.
.RE

.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(5) for descriptions of the following attributes:
.SS "/usr/bin/printf"
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
CSI	Enabled
_
Interface Stability	Committed
_
Standard	See \fBstandards\fR(5).
.TE

.SS "ksh93"
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Uncommitted
.TE

.SH SEE ALSO
.sp
.LP
\fBawk\fR(1), \fBbc\fR(1), \fBdate\fR(1), \fBecho\fR(1), \fBksh93\fR(1),
\fBprintf\fR(3C), \fBstrtod\fR(3C), \fBstrtol\fR(3C), \fBstrtoul\fR(3C),
\fBattributes\fR(5), \fBenviron\fR(5), \fBformats\fR(5), \fBstandards\fR(5)
.SH NOTES
.sp
.LP
Using format specifiers (characters following '%') which are not listed in the
\fBprintf\fR(3C) or this manual page will result in undefined behavior.
.sp
.LP
Using escape sequences (the character following a backslash ('\e')) which are
not listed in the \fBprintf\fR(3C) or this manual page will result in undefined
behavior.
.sp
.LP
Floating-point values follow C99, XPG6 and IEEE 754 standard behavior and can
handle values the same way as the platform's |\fBlong double\fR| datatype.
.sp
.LP
Floating-point values handle the sign separately which allows signs for values
like NaN (for example, -nan), Infinite (for example, -inf) and zero (for
example, -0.0).