(libc.info.gz) Formatted Output Basics

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(libc.info.gz) Formatted Output

(libc.info.gz) Output Conversion Syntax

 
 12.12.1 Formatted Output Basics
 -------------------------------
 
 The 'printf' function can be used to print any number of arguments.  The
 template string argument you supply in a call provides information not
 only about the number of additional arguments, but also about their
 types and what style should be used for printing them.
 
    Ordinary characters in the template string are simply written to the
 output stream as-is, while "conversion specifications" introduced by a
 '%' character in the template cause subsequent arguments to be formatted
 and written to the output stream.  For example,
 
      int pct = 37;
      char filename[] = "foo.txt";
      printf ("Processing of `%s' is %d%% finished.\nPlease be patient.\n",
      	filename, pct);
 
 produces output like
 
      Processing of `foo.txt' is 37% finished.
      Please be patient.
 
    This example shows the use of the '%d' conversion to specify that an
 'int' argument should be printed in decimal notation, the '%s'
 conversion to specify printing of a string argument, and the '%%'
 conversion to print a literal '%' character.
 
    There are also conversions for printing an integer argument as an
 unsigned value in octal, decimal, or hexadecimal radix ('%o', '%u', or
 '%x', respectively); or as a character value ('%c').
 
    Floating-point numbers can be printed in normal, fixed-point notation
 using the '%f' conversion or in exponential notation using the '%e'
 conversion.  The '%g' conversion uses either '%e' or '%f' format,
 depending on what is more appropriate for the magnitude of the
 particular number.
 
    You can control formatting more precisely by writing "modifiers"
 between the '%' and the character that indicates which conversion to
 apply.  These slightly alter the ordinary behavior of the conversion.
 For example, most conversion specifications permit you to specify a
 minimum field width and a flag indicating whether you want the result
 left- or right-justified within the field.
 
    The specific flags and modifiers that are permitted and their
 interpretation vary depending on the particular conversion.  They're all
 described in more detail in the following sections.  Don't worry if this
 all seems excessively complicated at first; you can almost always get
 reasonable free-format output without using any of the modifiers at all.
 The modifiers are mostly used to make the output look "prettier" in
 tables.
 

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(libc.info.gz) Formatted Output

(libc.info.gz) Output Conversion Syntax