printf - Writes formatted output
printf format [argument...]
Interfaces documented on this reference page conform to
industry standards as follows:
printf: XCU5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
None
A string describing the manner of writing the output. This
string is explained in the DESCRIPTION section. The
strings to be written under the control of the format.
These strings are explained in the DESCRIPTION section.
The printf command converts, formats, and writes its arguments
to the standard output. The values specified by the
argument variable are formatted under control of the format
variable.
Syntax of the argument Variable [Toc] [Back]
The argument variable is a list of one or more strings to
be written to the standard output under the control of the
format variable. These are treated as strings if the corresponding
conversion character is b, c, or s; otherwise,
it is evaluated as a C constant, with the following extensions:
A leading + (plus sign) or - (minus sign) is allowed.
If the leading character is a ' (single quote) or " (double
quote), the value is the numeric value in the underlying
code set of the character following the single quote
or double quote.
Syntax of the format Variable [Toc] [Back]
The format variable is a character string that contains
three types of objects: Plain characters that are copied
to the output stream. The following escape sequences are
both copied to the output stream and cause the associated
action to occur on display devices that are capable of the
action. Backslash Alert Backspace Formfeed Newline Carriage
Return Tab Vertical Tab Where ddd is a one-, two-,
or three-digit octal number. These escape sequences are
displayed as a byte with the numeric value specified by
the octal number. A delta character in the format string
is treated as a delta character, rather than as a space
character.
The format variable is reused as often as necessary to
satisfy the arguments. Any extra c or s 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.
Each conversion specification in the format variable has
the following syntax: A % (percent sign). Zero or more
options, which modify the meaning of the conversion specification.
The option characters and their meanings are as
follows: The result of the conversion is left aligned
within the field. The result of a signed conversion
always begins with a + (plus) or - (minus). If the first
character of a signed conversion is not a sign, a blank is
prefixed to the result. If both the blank and + options
appear, then the blank option is ignored. The value is
converted to an alternative form. For c, d, i, u, and s
conversions, the option has no effect. For o conversion,
it increases the precision to force the first digit of the
result to be a 0 (zero). For x and X conversions, a
nonzero result has 0x, or 0X prefixed to it, respectively.
For e, E, f, g, and G conversions, the result always contains
a radix character, even if no digits follow the
radix character. For g and G conversions, trailing zeros
are not removed from the result as they usually are. For
d, i, o, u, x, X, e, E, f, g, and G 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 0 (zero) and - options appear, the 0 (zero) option
is ignored. For d, i, o, u, x, and X conversions, if a
precision is specified, the 0 (zero) option is ignored.
An optional decimal digit string that specifies the minimum
field width. If the converted value has fewer characters
than the field width, the field is padded on the left
to the length specified by the field width. If the leftadjustment
option flag (-) is specified, the field is
padded on the right. An optional precision. The precision
is a (dot) followed by an asterisk (*), or a decimal digit
string. If no precision is given, it is treated as 0
(zero). The precision specifies: The minimum number of
digits to appear for the d, o, i, u, x, or X conversions.
The number of digits to appear after the radix character
for the e and f conversions. The maximum number of significant
digits for the g conversion. The maximum number
of bytes to be printed from a string in the s conversion.
A character that indicates the type of conversion to be
applied, as follows: Performs no conversion. Prints a %
(percent sign). Accepts a value as a string that may contain
backslash-escape sequences. Bytes from the converted
string are printed until the end of the string or number
of bytes indicated by the precision specification is
reached. If the precision is omitted, all bytes until the
first null character are printed.
The following backslash-escape sequences are supported:
The \Oddd sequence, where ddd is a one-,
two-, or three-digit octal number that is converted
to a byte with the numeric value specified by the
octal number. The escape sequences previously
listed under the description of the format variable.
These are converted to the individual characters
they represented. The \c sequence, which is
not displayed and causes the printf command to
ignore any remaining characters in the string
parameter containing it, any remaining string
parameters, and any additional characters in the
format variable. Prints the first character of the
argument. Accepts an integer value and converts it
to a signed decimal notation in the style [-]dddd.
The precision specifies the minimum number of digits
to appear. If the value being converted can be
represented in fewer digits, it is expanded with
leading zeros. The default precision is 1. The
result of converting a 0 (zero) value with a precision
of 0 (zero) is a null string. Specifying a
field width with a 0 (zero) as a leading character
causes the field to be padded with leading zeros.
Accepts a float or double value and converts it to
the exponential form [-] d.dde +|- dd. There is one
digit before the radix character (shown here as the
decimal point), and the number of digits after the
radix character is equal to the precision specification.
The LC_NUMERIC locale category determines
the radix character to use in this format. If no
precision is specified, then six digits are output.
If the precision is 0 (zero), then no radix character
appears. The E conversion character produces a
number with E instead of e before the exponent. The
exponent always contains at least two digits. However,
if the value to be printed requires an exponent
greater than two digits, additional exponent
digits are printed as necessary. Accepts a float
or double value and converts it to decimal notation
in the format [-] ddd.ddd. The number of digits
after the radix character (shown here as the decimal
point) is equal to the precision specification.
The LC_NUMERIC locale category determines the radix
character to use in this format. If no precision is
specified, then six digits are output. If the precision
is 0 (zero), then no radix character
appears. Accepts a float or double value and converts
it in the style of the f or e conversion
characters (or E in the case of the G conversion),
with the precision specifying the number of significant
digits. Trailing zeros are removed from the
result. A radix character appears only if it is
followed by a digit. The style used depends on the
value converted. Style g results only if the exponent
resulting from the conversion is less than -4,
or if it is greater than or equal to the precision.
Accepts an integer value and converts it to
unsigned octal notation. The precision specifies
the minimum number of digits to appear. If the
value being converted can be represented in fewer
digits, it is expanded with leading zeros. The
default precision is 1. The result of converting a
0 (zero) value with a precision of 0 (zero) is a
null string. Specifying a field width with a 0
(zero) as a leading character causes the field
width value to be padded with leading zeros. An
octal value for field width is not implied.
Accepts a value as a string, and bytes from the
string are printed until the end of the string is
encountered or the number of bytes indicated by the
precision is reached. If no precision is specified,
all characters up to the first null character are
printed. Accepts an integer value and converts it
to unsigned decimal notation. The precision specifies
the minimum number of digits to appear. If
the value being converted can be represented in
fewer digits, it is expanded with leading zeros.
The default precision is 1. The result of converting
a 0 (zero) value with a precision of 0 (zero)
is a null string. Specifying a field width with a 0
(zero) as a leading character causes the field
width value to be padded with leading zeros.
Accepts an integer value and converts it to
unsigned hexadecimal notation. The letters abcdef
are used for the x conversion and the letters
ABCDEF are used for the X conversion. The precision
specifies the minimum number of digits to appear.
If the value being converted can be represented in
fewer digits, it is expanded with leading zeros.
The default precision is 1. The result of converting
a 0 (zero) value with a precision of 0 (zero)
is a null string. Specifying a field width with a 0
(zero) as a leading character causes the field
width value to be padded with leading zeros.
If the result of a conversion is wider than the field
width, the field is expanded to contain the converted
result. No truncation occurs. However, a small precision
may cause truncation on the right.
The following printf command formats a series of numbers:
printf "%5d%4d\n" 1 21 321 4321 54321
This command produces the following output:
1 21
3214321 54321 0
The format variable is used three times to print
all of the given strings. The 0 (zero) is supplied
by the printf command to satisfy the last %4d conversion
specification. The following script
includes printf commands to alert the user (sound a
beep) and to display prompts for entering a name
and phone number. The script then appends the user
entries to a file.
printf "\aPlease fill in the following: \nName: "
read name printf "Phone number: " read phone echo
$name " " $phone >> phone_list echo >> phone_list
ENVIRONMENT VARIABLES [Toc] [Back] The following environment variables affect the execution
of printf: Provides a default value for the internationalization
variables that are unset or null. If LANG is unset
or null, the corresponding value from the default locale
is used. If any of the internationalization variables
contain an invalid setting, the utility behaves as if none
of the variables had been defined. If set to a non-empty
string value, overrides the values of all the other internationalization
variables. Determines the locale for the
interpretation of sequences of bytes of text data as characters
(for example, single-byte as opposed to multibyte
characters in arguments). Determines the locale for the
format and contents of diagnostic messages written to
standard error. Determines the location of message catalogues
for the processing of LC_MESSAGES. Determines the
locale for numbers written using the e, E, f, g, or G conversion
characters.
Commands: awk(1), bc(1), echo(1), read(1)
Functions: printf(3)
Standards: standards(5)
printf(1)
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