bash Cookbook

Avoiding “command not found” When Using Functions

Problem

You are used to other languages, such as Perl, which allow you to call a function in a section of your code that comes before the actual function definition.

Solution

Shell scripts are read and executed in a top-to-bottom linear way, so you must define any functions before you use them.

Discussion

Some other languages, such as Perl, go through intermediate steps during which the entire script is parsed as a unit. That allows you to write your code so that main() is at the top, and function (or subroutines) are defined later. By contrast, a shell script is read into memory and then executed one line at a time, so you can’t use a function before you define it.

See Also

• Defining Functions

• Using Functions: Parameters and Return Values

• Appendix C