PRINTF(1)PRINTF(1)NAMEprintf - write formatted output
SYNOPSIS
/usr/bin/printf
printf format [argument]...
ksh93
printf format [string...]
DESCRIPTION
/usr/bin/printf
The printf utility writes each string operand to standard output using
format to control the output format.
OPERANDS
/usr/bin/printf
The following operands are supported by /usr/bin/printf:
format
A string describing the format to use to write the remain‐
ing operands. The format operand is used as the format
string described on the formats(5) manual page, with the
following exceptions:
o A SPACE character in the format string, in any
context other than a flag of a conversion speci‐
fication, is treated as an ordinary character
that is copied to the output.
o A character in the format string is treated as a
character, not as a SPACE character.
o In addition to the escape sequences described on
the formats(5) manual page (\\, \a, \b, \f, \n,
\r, \t, \v), \ddd, where ddd is a one-, two- or
three-digit octal number, is written as a byte
with the numeric value specified by the octal
number.
o The program does not precede or follow output
from the d or u conversion specifications with
blank characters not specified by the format op‐
erand.
o The program does not precede output from the o
conversion specification with zeros not speci‐
fied by the format operand.
o The argument used for the conversion character
(or width or precision parameters, see below)
may be taken from the nnth argument instead of
the next unused argument, by specifying n$ imme‐
diately following the % character, or the *
character (for width or precision arguments).
If n$ appears in any conversions in the format
string, then it must be used for all conver‐
sions, including any variable width or precision
specifiers.
o The special character * 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 nth if
the form n$ is used), treating its value as a
decimal string.
o An additional conversion character, b, is sup‐
ported as follows. The argument is taken to be a
string that can contain backslash-escape
sequences. The following backslash-escape
sequences are supported:
o the escape sequences listed on the for‐
mats(5) manual page (\\, \a, \b, \f, \n, \r,
\t, \v), which are converted to the charac‐
ters they represent
o \0ddd, where ddd 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
o \c, which is written and 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.
The interpretation of a backslash followed by any other
sequence of characters is unspecified.
Bytes from the converted string are written until the end
of the string or the number of bytes indicated by the pre‐
cision specification is reached. If the precision is omit‐
ted, 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 format operand is reused
as often as necessary to satisfy the argument operands. Any
extra c or s conversion specifications are evaluated as if
a null string argument were supplied; other extra conver‐
sion specifications are evaluated as if a zero argument
were supplied.
When there are more argument operands than format speci‐
fiers, and the format includes n$ 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 nth argument previously encountered.
If the format operand contains no conversion specifications
and argument operands are present, the results are unspeci‐
fied. If a character sequence in the format operand begins
with a % character, but does not form a valid conversion
specification, the behavior is unspecified.
argument
The strings to be written to standard output, under the
control of format. The argument operands are treated as
strings if the corresponding conversion character is b, c
or s. Otherwise, it is evaluated as a C constant, as
described by the ISO C standard, with the following exten‐
sions:
o A leading plus or minus sign is allowed.
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.
If an argument operand cannot be completely converted into
an internal value appropriate to the corresponding conver‐
sion 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 oper‐
ands and writes the value accumulated at the time the error
was detected to standard output.
ksh93
The format operands support the full range of ANSI C/C99/XPG6 format‐
ting specifiers as well as additional specifiers:
%b
Each character in the string operand is processed specially, as
follows:
\a
Alert character.
\b
Backspace character.
\c
Terminate output without appending NEWLINE. The remaining
string operands are ignored.
\E
Escape character (ASCII octal 033).
\f
FORM FEED character.
\n
NEWLINE character.
\t
TAB character.
\v
Vertical tab character.
\\
Backslash character.
\0x
The 8-bit character whose ASCII code is the 1-, 2-, or
3-digit octal number x.
%B
Treat the argument as a variable name and output the value with‐
out converting it to a string. This is most useful for variables
of type -b.
%H
Output string with characters <, &, >, ", and non-printable char‐
acters, properly escaped for use in HTML and XML documents.
%P
Treat string as an extended regular expression and convert it to
a shell pattern.
%q
Output string quoted in a manner that it can be read in by the
shell to get back the same string. However, empty strings result‐
ing from missing string operands are not quoted.
%R
Treat string as an shell pattern expression and convert it to an
extended regular expression.
%T
Treat string as a date/time string and format it. The T can be
preceded by (dformat), where dformat is a date format as defined
by the date(1) command.
%Z
Output a byte whose value is 0.
When performing conversions of string to satisfy a numeric format spec‐
ifier, if the first character of string is "or', the value is the
numeric value in the underlying code set of the character following the
"or'. Otherwise, string is treated like a shell arithmetic expression
and evaluated.
If a string operand cannot be completely converted into a value appro‐
priate for that format specifier, an error occurs, but remaining string
operands continue to be processed.
In addition to the format specifier extensions, the following exten‐
sions of ANSI C/C99/XPG6 are permitted in format specifiers:
o The escape sequences \E and \e expand to the escape charac‐
ter which is octal 033 in ASCII.
o The escape sequence \cx expands to CTRL-x.
o The escape sequence \C[.name.] expands to the collating ele‐
ment name.
o The escape sequence \x{hex} expands to the character corre‐
sponding to the hexadecimal value hex.
o The format modifier flag = can be used to center a field to
a specified width. When the output is a terminal, the char‐
acter width is used rather than the number of bytes.
o Each of the integral format specifiers can have a third mod‐
ifier after width and precision that specifies the base of
the conversion from 2 to 64. In this case, the # modifier
causes base# to be prepended to the value.
o The # modifier can be used with the d specifier when no base
is specified to cause the output to be written in units of
1000 with a suffix of one of k M G T P E.
o The # modifier can be used with the i specifier to cause the
output to be written in units of 1024 with a suffix of one
of Ki Mi Gi Ti Pi Ei.
If there are more string operands than format specifiers, the format
string is reprocessed from the beginning. If there are fewer string op‐
erands than format specifiers, then string specifiers are treated as if
empty strings were supplied, numeric conversions are treated as if 0
was supplied, and time conversions are treated as if now was supplied.
When there are more argument operands than format specifiers, and the
format includes n$ 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 nth argument previously encoun‐
tered.
/usr/bin/printf is equivalent to ksh93's printf built-in and print -f,
which allows additional options to be specified.
USAGE
/usr/bin/printf
The printf utility, like the printf(3C) function on which it is based,
makes no special provision for dealing with multi-byte characters when
using the %c conversion specification. Applications should be extremely
cautious using either of these features when there are multi-byte char‐
acters in the character set.
The %b 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 echo utility. See also
the USAGE section of the echo(1) manual page for ways to use printf as
a replacement for all of the traditional versions of the echo utility.
If an argument cannot be parsed correctly for the corresponding conver‐
sion specification, the printf 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.
It is not considered an error if an argument operand is not completely
used for a c or s conversion or if a string operand's first or second
character is used to get the numeric value of a character.
EXAMPLES
/usr/bin/printf
Example 1 Printing a Series of Prompts
The following example alerts the user, then prints and reads a series
of prompts:
example% printf "\aPlease fill in the following: \nName: "
read name
printf "Phone number: "
read phone
Example 2 Printing a Table of Calculations
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:
example% while read right wrong ; do
percent=$(echo "scale=1;($right*100)/($right+$wrong)" | bc)
printf "%2d right\t%2d wrong\t(%s%%)\n" \
$right $wrong $percent
done < database_file
Example 3 Printing number strings
The command:
example% printf "%5d%4d\n" 1 21 321 4321 54321
produces:
1 21
3214321
54321 0
The format operand is used three times to print all of the given
strings and that a 0 was supplied by printf to satisfy the last %4d
conversion specification.
Example 4 Tabulating Conversion Errors
The following example tabulates conversion errors.
The printf 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 %d is speci‐
fied as the format operand:
┌───────────────────────────────────────────────────────────────────┐
│ 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 │
└───────────────────────────────────────────────────────────────────┘
The value shown on standard output is what would be expected as the
return value from the function strtol(3C). A similar correspondence
exists between %u and strtoul(3C), and %e, %f and %g and strtod(3C).
Example 5 Printing Output for a Specific Locale
The following example prints output for a specific locale. In a locale
using the ISO/IEC 646:1991 standard as the underlying codeset, the com‐
mand:
example% printf "%d\n" 3 +3 -3 \'3 \"+3 "'-3"
produces:
┌──────────────────────────────────┐
│3 Numeric value of constant 3 │
│3 Numeric value of constant 3 │
│−3 Numeric value of constant −3 │
│51 Numeric value of the charac‐ │
│ ter `3' in the ISO/IEC │
│ 646:1991 standard codeset │
│43 Numeric value of the charac‐ │
│ ter `+' in the ISO/IEC │
│ 646:1991 standard codeset │
│45 Numeric value of the charac‐ │
│ ter `−' in the SO/IEC │
│ 646:1991 standard codeset │
└──────────────────────────────────┘
In a locale with multi-byte characters, the value of a character is
intended to be the value of the equivalent of the wchar_t representa‐
tion of the character.
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.
Example 6 Alternative floating point representation 1
The printf utility supports an alternative floating point representa‐
tion (see printf(3C) entry for the "%a"/"%A"), which allows the output
of floating-point values in a format that avoids the usual base16 to
base10 rounding errors.
example% printf "%a\n" 2 3.1 NaN
produces:
0x1.0000000000000000000000000000p+01
0x1.8ccccccccccccccccccccccccccdp+01
nan
Example 7 Alternative floating point representation 2
The following example shows two different representations of the same
floating-point value.
example% x=2 ; printf "%f == %a\n" x x
produces:
2.000000 == 0x1.0000000000000000000000000000p+01
Example 8 Output of unicode values
The following command will print the EURO unicode symbol (code-point
0x20ac).
example% LC_ALL=en_US.UTF-8 printf "[20ac]\n"
produces:
<euro>
where "<euro>" represents the EURO currency symbol character.
Example 9 Convert unicode character to unicode code-point value
The following command will print the hexadecimal value of a given char‐
acter.
example% export LC_ALL=en_US.UTF-8
example% printf "%x\n" "'<euro>"
where "<euro>" represents the EURO currency symbol character (code-
point 0x20ac).
produces:
20ac
Example 10 Print the numeric value of an ASCII character
example% printf "%d\n" "'A"
produces:
65
Example 11 Print the language-independent date and time format
To print the language-independent date and time format, the following
statement could be used:
example% printf "format" weekday month day hour min
For example,
$ printf format "Sunday" "July" 3 10 2
For American usage, format could be the string:
"%s, %s %d, %d:%.2d\n"
producing the message:
Sunday, July 3, 10:02
Whereas for EU usage, format could be the string:
"%1$s, %3$d. %2$s, %4$d:%5$.2d\n"
Note that the '$' characters must be properly escaped, such as
"%1\$s, %3\$d. %2\$s, %4\$d:%5\$.2d\n" in this case
producing the message:
Sunday, 3. July, 10:02
ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables
that affect the execution of printf: LANG, LC_ALL, LC_CTYPE, LC_MES‐
SAGES, LC_NUMERIC, and NLSPATH.
EXIT STATUS
The following exit values are returned:
0
Successful completion.
>0
An error occurred.
ATTRIBUTES
See attributes(5) for descriptions of the following attributes:
/usr/bin/printf
┌────────────────────┬───────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼───────────────────┤
│CSI │ Enabled │
├────────────────────┼───────────────────┤
│Interface Stability │ Committed │
├────────────────────┼───────────────────┤
│Standard │ See standards(5). │
└────────────────────┴───────────────────┘
ksh93
┌────────────────────┬─────────────────┐
│ ATTRIBUTE TYPE │ ATTRIBUTE VALUE │
├────────────────────┼─────────────────┤
│Interface Stability │ Uncommitted │
└────────────────────┴─────────────────┘
SEE ALSOawk(1), bc(1), date(1), echo(1), ksh93(1), printf(3C), strtod(3C), str‐
tol(3C), strtoul(3C), attributes(5), environ(5), formats(5), stan‐
dards(5)NOTES
Using format specifiers (characters following '%') which are not listed
in the printf(3C) or this manual page will result in undefined behav‐
ior.
Using escape sequences (the character following a backslash ('\'))
which are not listed in the printf(3C) or this manual page will result
in undefined behavior.
Floating-point values follow C99, XPG6 and IEEE 754 standard behavior
and can handle values the same way as the platform's |long double|
datatype.
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).
May 11, 2014 PRINTF(1)
