Contents
How to use a variable in regex in Bash?
First, whenever you’re using the value of a variable, you need to write $line. Also, note that read line strips off leading and trailing whitespace, and allows the sequence backslash-newline as a line continuation. To retain whitespace, use IFS= read.
How to pick out match groups in Bash?
This works because =~ stores each match group in your regex in a different position in the BASH_REMATCH variable, so we’re able to pick out the groups with the names and values and perform an indirect assignment ( printf -v varname %s “$value” stores value in varname ).
How to test the value of a variable in Bash?
If you want to test that the line contains $key (so for example if the value of key is fu*bar then hellofu*bar and fu*barqux match, but fuubar and gu*bar don’t), then use the == operator and again make sure to put $key in double quotes.
When to write read line or variable in Bash?
Here’s your script corrected: First, whenever you’re using the value of a variable, you need to write $line. Also, note that read line strips off leading and trailing whitespace, and allows the sequence backslash-newline as a line continuation.
How are variables referenced in a bash script?
They’re referenced as $1 for the first parameter, $2 as the second, and so on, up to $9 for the ninth parameter. (Actually, there’s a $0, as well, but that’s reserved to always hold the script.) You can reference command line parameters in a script just as you would regular variables.
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.