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NetBSD 6.1.5 - man page for printf (netbsd section 1)

PRINTF(1)			   BSD General Commands Manual				PRINTF(1)

NAME
     printf -- formatted output

SYNOPSIS
     printf format [arguments ...]

DESCRIPTION
     printf formats and prints its arguments, after the first, under control of the format.  The
     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 argument.

     The arguments after the first are treated as strings if the corresponding format is either
     b, B, c, or s; otherwise it is evaluated as a C constant, with the following extensions:

	   o   A leading plus or minus sign is allowed.
	   o   If the leading character is a single or double quote, the value is the ASCII code
	       of the next character.

     The format string is reused as often as necessary to satisfy the arguments.  Any extra for-
     mat specifications are evaluated with zero or the null string.

     Character escape sequences are in backslash notation as defined in ANSI X3.159-1989
     (``ANSI C89'').  The characters and their meanings are as follows:

	   \e	   Write an <escape> character.

	   \a	   Write a <bell> character.

	   \b	   Write a <backspace> character.

	   \f	   Write a <form-feed> character.

	   \n	   Write a <new-line> character.

	   \r	   Write a <carriage return> character.

	   \t	   Write a <tab> character.

	   \v	   Write a <vertical tab> character.

	   \'	   Write a <single quote> character.

	   \"	   Write a <double quote> character.

	   \\	   Write a backslash character.

	   \num    Write an 8-bit character whose ASCII value is the 1-, 2-, or 3-digit octal
		   number num.

	   \xxx    Write an 8-bit character whose ASCII value is the 1- or 2-digit hexadecimal
		   number xx.

     Each format specification is introduced by the percent character (``%'').	The remainder of
     the format specification includes, in the following order:

     Zero or more of the following flags:

	     #	     A '#' character specifying that the value should be printed in an
		     ``alternative form''.  For b, c, d, and s formats, this option has no
		     effect.  For the o format the precision of the number is increased to force
		     the first character of the output string to a zero.  For the x (X) format, a
		     non-zero result has the string 0x (0X) prepended to it.  For e, E, f, g, and
		     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 g and G formats,
		     trailing zeros are not removed from the result as they would otherwise be.

	     -	     A minus sign '-' which specifies left adjustment of the output in the indi-
		     cated field;

	     +	     A '+' character specifying that there should always be a sign placed before
		     the number when using signed formats.

	     ' '     A space specifying that a blank should be left before a positive number for
		     a signed format.  A '+' overrides a space if both are used;

	     0	     A zero `0' character indicating that zero-padding should be used rather than
		     blank-padding.  A '-' overrides a '0' if both are used;

     Field Width:
	     An optional digit string specifying a 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);

     Precision:
	     An optional period, '.', followed by an optional digit string giving a precision
	     which specifies the number of digits to appear after the decimal point, for e and f
	     formats, or the maximum number of characters to be printed from a string (b, B, and
	     s formats); if the digit string is missing, the precision is treated as zero;

     Format:
	     A character which indicates the type of format to use (one of diouxXfwEgGbBcs).

     A field width or precision may be '*' instead of a digit string.  In this case an argument
     supplies the field width or precision.

     The format characters and their meanings are:

     diouXx	 The argument is printed as a signed decimal (d or i), unsigned octal, unsigned
		 decimal, or unsigned hexadecimal (X or x), respectively.

     f		 The argument is printed in the style [-]ddd.ddd 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.

     eE 	 The argument is printed in the style [-]d.ddde+-dd where there is one digit
		 before the decimal point and the number after is equal to the precision specifi-
		 cation for the argument; when the precision is missing, 6 digits are produced.
		 An upper-case E is used for an 'E' format.

     gG 	 The argument is printed in style f or in style e (E) whichever gives full preci-
		 sion in minimum space.

     b		 Characters from the string argument are printed with backslash-escape sequences
		 expanded.

		 The following additional backslash-escape sequences are supported:

		 \c	 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.

		 \0num	 Write an 8-bit character whose ASCII value is the 1-, 2-, or 3-digit
			 octal number num.

		 \^c	 Write the control character c.  Generates characters `\000' through
			 `\037`, and `\177' (from `\^?').

		 \M-c	 Write the character c with the 8th bit set.  Generates characters `\241'
			 through `\376`.

		 \M^c	 Write the control character c with the 8th bit set.  Generates charac-
			 ters `\200' through `\237`, and `\377' (from `\M^?').

     B		 Characters from the string argument are printed with unprintable characters
		 backslash-escaped using the `\c',`\^c',`\M-c'or `\M^c', formats described above.

     c		 The first character of argument is printed.

     s		 Characters from the string 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.

     %		 Print a `%'; no argument is used.

     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.

EXIT STATUS
     printf exits 0 on success, 1 on failure.

SEE ALSO
     echo(1), printf(3), vis(3), printf(9)

STANDARDS
     The printf utility conforms to IEEE Std 1003.1-2001 (``POSIX.1'').

     Support for the floating point formats and `*' as a field width and precision are optional
     in POSIX.

     The behaviour of the %B format and the \', \", \xxx, \e and \[M][-|^]c escape sequences are
     undefined in POSIX.

BUGS
     Since the floating point numbers are translated from ASCII to floating-point and then back
     again, floating-point precision may be lost.

     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.

NOTES
     All formats which treat the argument as a number first convert the argument from its exter-
     nal representation as a character string to an internal numeric representation, and then
     apply the format to the internal numeric representation, producing another external charac-
     ter string representation.  One might expect the %c format to do likewise, but in fact it
     does not.

     To convert a string representation of a decimal, octal, or hexadecimal number into the cor-
     responding character, two nested printf invocations may be used, in which the inner invoca-
     tion 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:

	   printf "$(printf "\\%o" "0x0A")"

BSD					   May 6, 2008					      BSD


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