(octave.info)Input Conversion Syntax

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14.2.12 Input Conversion Syntax
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A ‘scanf’ template string is a string that contains ordinary multibyte
characters interspersed with conversion specifications that start with
‘%’.

   Any whitespace character in the template causes any number of
whitespace characters in the input stream to be read and discarded.  The
whitespace characters that are matched need not be exactly the same
whitespace characters that appear in the template string.  For example,
write ‘ , ’ in the template to recognize a comma with optional
whitespace before and after.

   Other characters in the template string that are not part of
conversion specifications must match characters in the input stream
exactly; if this is not the case, a matching failure occurs.

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

     % FLAGS WIDTH TYPE CONVERSION

   In more detail, an input conversion specification consists of an
initial ‘%’ character followed in sequence by:

   • An optional “flag character” ‘*’, which says to ignore the text
     read for this specification.  When ‘scanf’ finds a conversion
     specification that uses this flag, it reads input as directed by
     the rest of the conversion specification, but it discards this
     input, does not return any value, and does not increment the count
     of successful assignments.

   • An optional decimal integer that specifies the “maximum field
     width”.  Reading of characters from the input stream stops either
     when this maximum is reached or when a non-matching character is
     found, whichever happens first.  Most conversions discard initial
     whitespace characters, and these discarded characters don’t count
     towards the maximum field width.  Conversions that do not discard
     initial whitespace are explicitly documented.

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

   • 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 allow.