CHAPTER 4Command-Line Parsing and Expansion

One of the strengths of the shell as a programming language is its parsing of command-line arguments and the various expansions it performs on words in the line. When a command is called with arguments, the shell does several things before it invokes the command.

To help visualize what happens, the short script shown in Listing 4-1, called sa, will display what the shell has passed to it after processing all the arguments. Each of its arguments is printed on a separate line, preceded by the value of $pre and followed by the value of $post.

Listing 4-1. sa; Displaying Command-Line Arguments

pre=: post=: printf "$pre%s$post\n" "$@"

The special parameter $@ expands to a list of all the command-line ...

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