(gawk) Function Calls

Info Catalog

(gawk) Conditional Exp

(gawk) Expressions

(gawk) Precedence

 
 Function Calls
 ==============
 
    A "function" is a name for a particular calculation.  Because it has
 a name, you can ask for it by name at any point in the program.  For
 example, the function `sqrt' computes the square root of a number.
 
    A fixed set of functions are "built-in", which means they are
 available in every `awk' program.  The `sqrt' function is one of these.
  Built-in Functions Built-in, for a list of built-in functions
 and their descriptions.  In addition, you can define your own functions
 for use in your program.   User-defined Functions User-defined,
 for how to do this.
 
    The way to use a function is with a "function call" expression,
 which consists of the function name followed immediately by a list of
 "arguments" in parentheses.  The arguments are expressions which
 provide the raw materials for the function's calculations.  When there
 is more than one argument, they are separated by commas.  If there are
 no arguments, write just `()' after the function name.  Here are some
 examples:
 
      sqrt(x^2 + y^2)        one argument
      atan2(y, x)            two arguments
      rand()                 no arguments
 
    *Do not put any space between the function name and the
 open-parenthesis!*  A user-defined function name looks just like the
 name of a variable, and space would make the expression look like
 concatenation of a variable with an expression inside parentheses.
 Space before the parenthesis is harmless with built-in functions, but
 it is best not to get into the habit of using space to avoid mistakes
 with user-defined functions.
 
    Each function expects a particular number of arguments.  For
 example, the `sqrt' function must be called with a single argument, the
 number to take the square root of:
 
      sqrt(ARGUMENT)
 
    Some of the built-in functions allow you to omit the final argument.
 If you do so, they use a reasonable default.   Built-in Functions
 Built-in, for full details.  If arguments are omitted in calls to
 user-defined functions, then those arguments are treated as local
 variables, initialized to the empty string ( User-defined
 Functions User-defined.).
 
    Like every other expression, the function call has a value, which is
 computed by the function based on the arguments you give it.  In this
 example, the value of `sqrt(ARGUMENT)' is the square root of ARGUMENT.
 A function can also have side effects, such as assigning values to
 certain variables or doing I/O.
 
    Here is a command to read numbers, one number per line, and print the
 square root of each one:
 
      $ awk '{ print "The square root of", $1, "is", sqrt($1) }'
      1
      -| The square root of 1 is 1
      3
      -| The square root of 3 is 1.73205
      5
      -| The square root of 5 is 2.23607
      Control-d
 

Info Catalog

(gawk) Conditional Exp

(gawk) Expressions

(gawk) Precedence