One of the way to use this feature is using the terminal.
1. Open the terminal
say hello world!
orsay "hello world!"
Apparently there is not difference between both commands. Actually, the second one is recommended, because with it, the command recognize the input as single text. One of the advantage of it is it can skip symbols as "(".
There are several interesting options
Save the voice as sound file
You can save the speak voice as sound file. The default format is aac. You can always changing it by specifying exactly the format you want
Here is a sample:
say -o hi.aac "hello world!"
Read from a txt file
The program can read the text from an txt file. For example, you might have an txt file called helloWorld.txt, which contains the follow string:
To read, you just has to type on the terminal:
say -f "helloWord"
Change the voice
This function is much more funnier if we switch the speaker. By default, it has several voices, from someone who has a REAL FROG in the throat to a PRINCESS.
To check the complete list, type:
say -v ?
Choose the speaker by typing her name. For example, for the princess, you should type
say -v Princess "hello world!"
For more information, here is the complete and official man page: