Understanding default parameters
Many times we may pass certain parameters from the command line; sometimes, we may not pass any parameters at all. We may need to have certain default values to be initialized to certain variables.
We will understand this concept by the following script.
Create a default_argument_1.sh
script as follows:
#!/bin/bash MY_PARAM=${1:-default} echo $MY_PARAM
Execute the script and check:
$ chmod +x default_argument_1.sh One $ ./default_argument_1.sh One One $ ./default_argument_1.sh default
Create another default_argument_2.sh
script:
#!/bin/bash variable1=$1 variable2=${2:-$variable1} echo $variable1 echo $variable2
Output:
We executed the script two times:
- When we passed two arguments, then
variable1
was$1
andvariable2
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