Updated: 2021/Apr/14


PRINTF(1)                   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:

              A leading plus or minus sign is allowed.

              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 format 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, 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 indicated field;

            +           A plus sign which specifies that there should always
                        be a sign placed before the number when using signed
                        formats.

            ` '         A <space> character which specifies that a space
                        should be left before a positive number for a signed
                        format.  A `+' overrides a <space> if both are used;

            0           A digit zero character which specifies that zero-
                        padding should be used rather than space-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 space-
            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
            diouxXfFeEgGaAbBcs).

     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, which must represent an integer constant, with
                 an optional leading plus or minus sign, is printed as a
                 signed decimal (d or i), unsigned octal (o), unsigned decimal
                 (u), or unsigned hexadecimal (X or x).

     fF          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.  If
                 the number is Infinity, or Not-a-Number, then `inf' or `nan'
                 is printed for f format, and `INF' or `NAN' for F format.

     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 specification for the
                 argument; when the precision is missing, 6 digits are
                 produced.  An upper-case `E' is used for an E format, and
                 upper-case for Infinity and NaN as for F format.

     gG          The argument is printed in style f (F) or in style e (E)
                 whichever gives full precision in minimum space.

     aA          The argument is treated as a floating point number, for which
                 the underlying hexadecimal representation is printed.  See
                 printf(3) for the details.

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

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

     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 literal percent character (`%'); 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.

     If the first character of format is a dash, format must be preceded by a
     word consisting of two dashes (`--') to prevent it from being interpreted
     as an option string.

EXIT STATUS
     The printf utility exits 0 on success, and >0 if an error occurs.

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 \', \", \e, \num, 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 external representation as a character string to an
     internal numeric representation, and then apply the format to the
     internal numeric representation, producing another external character
     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 corresponding character, two nested printf invocations
     may be used, in which the inner invocation 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)"

NetBSD 9.99                     August 31, 2018                    NetBSD 9.99