Here is an example of how Bash scripts utilize certain special variables:
#!/bin/bash
# Display the process ID of the current script
echo "Process ID: $$"
# Display the path of the current script
echo "Current script path: $0"
# Display the number of arguments passed to the script
echo "Number of arguments: $#"
# Display the first and second arguments
echo "First argument: $1"
echo "Second argument: $2"
# Display all arguments
echo "List of all arguments: $@"
# Display all arguments as a single string
echo "All arguments as a string: $*"
# Iterate over each argument
params=$@
for param in $params; do
echo "Parameter: $param"
done
# Check if the first argument is 123
# Exit with status 0 if true, 1 otherwise
if [[ $1 = 123 ]]; then
echo "Exit status: $?"
exit 0
else
echo "Exit status: $?"
exit 1
fi
When running the script with a few arguments, you can expect the following output:
$ ./hello003.sh arg1 arg2 arg3
Process ID: 640234
Current script path: ./hello003.sh
Number of arguments: 3
First argument: arg1
Second argument: arg2
List of all arguments: arg1 arg2 arg3
All arguments as a string: arg1 arg2 arg3
Parameter: arg1
Parameter: arg2
Parameter: arg3
Exit status: 1
This script demonstrates the use of special variables in Bash, such as $$, $0, $#, $1, $2, $@, and $?. These variables contain useful information about the script itself and the arguments that are passed to it.