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GNU Info (gawk.info)Function CallsFunction Calls ============== A "function" is a name for a particular calculation. This enables you to 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. Note: Built-in Functions, for a list of built-in functions and their descriptions. In addition, you can define functions for use in your program. Note: User-Defined Functions, for instructions on 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 that 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, just write `()' after the function name. The following examples show function calls with and without arguments: sqrt(x^2 + y^2) one argument atan2(y, x) two arguments rand() no arguments *Caution:* 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--a space would make the expression look like concatenation of a variable with an expression inside parentheses. With built-in functions, space before the parenthesis is harmless, 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 have one or more optional arguments. If those arguments are not supplied, the functions use a reasonable default value. Note: Built-in Functions, for full details. If arguments are omitted in calls to user-defined functions, then those arguments are treated as local variables and initialized to the empty string (Note: User-Defined Functions.). 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. The following program reads numbers, one number per line, and prints 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 Ctrl-d automatically generated by info2www version 1.2.2.9 |