How are variables and command substitution used in Bash?
Bash variables and command substitution Using variables to refer to data, including the results of a command. An essential feature of programming is the ability to use a name or a label to refer to some other quantity: such as a value, or a command. This is commonly referred to as variables.
How are parameter expansion modifiers used in Bash?
You can use it for manipulating and expanding variables on demands without using external commands such as perl, python, sed or awk. This guide shows you how to use parameter expansion modifiers to transform Bash shell variables for your scripting needs. You can use variables to store data and configuration options.
How to change the value of a global variable in Bash?
Using process substitution instead (this is the < < (commands) syntax) keeps everything in the same process, so changes to global variables are possible. One less invocation of grep to worry about. This somewhat by-passes your question (and it’s a good question), but you can achieve the same results using simply:
How are pipes executed in a subshell in Bash?
Pipes are executed in a subshell, as noted by Blagovest in his comment. Using process substitution instead (this is the < < (commands) syntax) keeps everything in the same process, so changes to global variables are possible. One less invocation of grep to worry about.
When to use parameter substitution in a variable?
Parameter Substitution Same as $parameter, i.e., value of the variable parameter . In certain contexts, only the less ambiguous $ {parameter} form works. May be used for concatenating variables with strings. If parameter not set, use default.
How to substitute a parameter in Linux command line?
# Set $DISKS to $1 command-line-parameter, #+ or to $E_NOPARAM if that is unset. See also Example 3-4, Example 31-2, and Example A-6. Compare this method with using an and list to supply a default command-line argument. If parameter not set, set it to default.