Shell Programming and Scripting

In one of the shell script (Where abinitio graph is called), the last line is wait ${!}. What does this wait ${!} mean ???

${!} an alternate syntax for $! which is the PID of the last background command (presumably here, your graph application). The script simply waits for the application to finish.

Generally, ${anything} is just another way to write $anything -- in some situations, the braces are required for disambiguation (${anything}too means something else than $anythingtoo which means ${anythingtoo}) but some people like to put them everywhere just out of habit, or for clarity.

Perform the following, you will come to know:

Code:

- a man of wait command
- and the following example: 

$ sleep 10 &
[2] 9110

$ wait ${!}

And

Code:

$! :: PID of last background process

//Jadu