Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
PRINTF(1)               FreeBSD General Commands Manual              PRINTF(1)

     printf -- formatted output

     printf format [arguments ...]

     The printf utility formats and prints its arguments, after the first,
     under control of the format.  The format is a character string which con-
     tains 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 c, b 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 format specifications are evaluated with zero or
     the null string.

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

           \a      Write a <bell> character.
           \b      Write a <backspace> character.
           \c      Ignore remaining characters in this string.
           \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 backslash character.
           \0num   Write an 8-bit character whose ASCII value is the 1-, 2-,
                   or 3-digit octal number num.

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

     Zero or more of the following flags:

             #       A `#' character specifying that the value should be
                     printed in an ``alternate form''.  For c, d, and s, for-
                     mats, this option has no effect.  For the o formats 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 fol-
                     lows the decimal point).  For g and G formats, trailing
                     zeros are not removed from the result as they would oth-
                     erwise be;

             -       A minus sign `-' which specifies left adjustment of the
                     output in the indicated 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 indi-
             cator 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

             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 num-
             ber of characters to be printed from a string; if the digit
             string is missing, the precision is treated as zero;

             A character which indicates the type of format to use (one of
             diouxXfFeEgGaAcsb).  The uppercase formats differ from their low-
             ercase counterparts only in that the output of the former is
             entirely in uppercase.  The floating-point format specifiers
             (fFeEgGaA) may be prefixed by an L to request that additional
             precision be used, if available.

     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.

     fF          The argument is printed in the style `[-]ddd.ddd' where the
                 number of d's after the decimal point is equal to the preci-
                 sion 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.  The values
                 infinity and NaN are printed as `inf' and `nan', respec-

     eE          The argument is printed in the style e `[-d.ddd+-dd]' where
                 there is one digit before the decimal point and the number
                 after is equal to the precision specification for the argu-
                 ment; when the precision is missing, 6 digits are produced.
                 The values infinity and NaN are printed as `inf' and `nan',

     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 printed in style `[-h.hhh+-pd]' where there
                 is one digit before the hexadecimal point and the number
                 after is equal to the precision specification for the argu-
                 ment; when the precision is missing, enough digits are pro-
                 duced to convey the argument's exact double-precision float-
                 ing-point representation.  The values infinity and NaN are
                 printed as `inf' and `nan', respectively.

     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; however if the precision
                 is 0 or missing, all characters in the string are printed.

     b           As for s, but interpret character escapes in backslash nota-
                 tion in the string argument.

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

     The decimal point character is defined in the program's locale (category

     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.

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

     The traditional BSD behavior of converting arguments of numeric formats
     not beginning with a digit to the ASCII code of the first character is
     not supported.

     echo(1), printf(3)

     The printf command is expected to be compatible with the IEEE Std 1003.2
     (``POSIX.2'') specification.

     The printf command appeared in 4.3BSD-Reno.  It is modeled after the
     standard library function, printf(3).

     Since the floating point numbers are translated from ASCII to floating-
     point and then back again, floating-point precision may be lost.  (By
     default, the number is translated to an IEEE-754 double-precision value
     before being printed.  The L modifier may produce additional precision,
     depending on the hardware platform.)

     ANSI hexadecimal character constants were deliberately not provided.

     The escape sequence \000 is the string terminator.  When present in the
     argument for the b format, the argument will be truncated at the \000

     Multibyte characters are not recognized in format strings (this is only a
     problem if `%' can appear inside a multibyte character).

FreeBSD 6.2                     April 14, 2005                     FreeBSD 6.2


Want to link to this manual page? Use this URL:

home | help