(octave.info)Output Conversion Syntax

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14.2.6 Output Conversion Syntax
-------------------------------

This section provides details about the precise syntax of conversion
specifications that can appear in a ‘printf’ template string.

   Characters in the template string that are not part of a conversion
specification are printed as-is to the output stream.

   The conversion specifications in a ‘printf’ template string have the
general form:

     % FLAGS WIDTH [ . PRECISION ] TYPE CONVERSION

   For example, in the conversion specifier ‘%-10.8ld’, the ‘-’ is a
flag, ‘10’ specifies the field width, the precision is ‘8’, the letter
‘l’ is a type modifier, and ‘d’ specifies the conversion style.  (This
particular type specifier says to print a numeric argument in decimal
notation, with a minimum of 8 digits left-justified in a field at least
10 characters wide.)

   In more detail, output conversion specifications consist of an
initial ‘%’ character followed in sequence by:

   • Zero or more “flag characters” that modify the normal behavior of
     the conversion specification.

   • An optional decimal integer specifying the “minimum field width”.
     If the normal conversion produces fewer characters than this, the
     field is padded with spaces to the specified width.  This is a
     _minimum_ value; if the normal conversion produces more characters
     than this, the field is _not_ truncated.  Normally, the output is
     right-justified within the field.

     You can also specify a field width of ‘*’.  This means that the
     next argument in the argument list (before the actual value to be
     printed) is used as the field width.  The value is rounded to the
     nearest integer.  If the value is negative, this means to set the
     ‘-’ flag (see below) and to use the absolute value as the field
     width.

   • An optional “precision” to specify the number of digits to be
     written for the numeric conversions.  If the precision is
     specified, it consists of a period (‘.’) followed optionally by a
     decimal integer (which defaults to zero if omitted).

     You can also specify a precision of ‘*’.  This means that the next
     argument in the argument list (before the actual value to be
     printed) is used as the precision.  The value must be an integer,
     and is ignored if it is negative.

   • An optional “type modifier character”.  This character is ignored
     by Octave’s ‘printf’ function, but is recognized to provide
     compatibility with the C language ‘printf’.

   • A character that specifies the conversion to be applied.

   The exact options that are permitted and how they are interpreted
vary between the different conversion specifiers.  See the descriptions
of the individual conversions for information about the particular
options that they use.