Contents
What are the different types of expansion in Bash?
There are seven kinds of expansion performed: Expansion of expressions within braces. Expansion of the ~ character. How Bash expands variables to their values. Using the output of a command as an argument. How to use arithmetic in shell expansions. A way to write and read to and from a command.
How is an expansion performed in a shell?
After the command has been split into tokens (see Section 1.4.1.1 ), these tokens or words are expanded or resolved. There are eight kinds of expansion performed, which we will discuss in the next sections, in the order that they are expanded. After all expansions, quote removal is performed. 3.4.2. Brace expansion
When do you use indirect expansion in Bash?
If the first character of “PARAMETER” is an exclamation point, Bash uses the value of the variable formed from the rest of “PARAMETER” as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of “PARAMETER” itself. This is known as indirect expansion.
Is the string$ { eligible for expansion in Bash?
Bash does not apply any syntactic interpretation to the context of the expansion or the text between the braces. To avoid conflicts with parameter expansion, the string “$ {” is not considered eligible for brace expansion.
How to expand the value of a command in Bash?
Bash has a fairly consistent syntax with regards to value expansions: they all start with a $ symbol. Command Substitution essentially expands the value of a command that was executed in a subshell. As such, the syntax is a combination of the value-expansion prefix $ followed by the subshell to expand: (…).
How to perform pathname expansions in Bash shell?
Bash can perform all sorts of pathname expansions for us. To perform a pathname expansion, we simply write a syntactical glob pattern in the place where we want to expand pathnames. A glob is the name of the type of pattern supported by the bash shell.
How are expansions performed on the command line?
Expansion is performed on the command line after it has been split into token s. There are seven kinds of expansion performed: Expansion of expressions within braces. Expansion of the ~ character.