2. is_valid_pkg.sh

The unqualified name of a Java package should obey the following rules:

• the first character of the name must be a lowercase English letter
• all other characters of the name must be a lowercase English letter, a digit, or an underscore _ character

(The fully qualified name of a package is made up of unqualified package names separated by ., but this question does not deal with fully qualified package names)

Write a script named is_valid_pkg.sh requiring exactly one command line argument that is taken to be a possible package name. The script sets its exit status to 0 if the command line argument is a valid unqualified package name, otherwise it sets its exit status to 1.

Error checking:If the number of command line arguments is not equal to one, then the script prints an error message to standard error and exits with a status of 2.

Examples (comments indicate the expected output and are not part of the command):

is_valid_pkg.sh util; echo $? # 0

is_valid_pkg.sh big_hero6; echo $? # 0

is_valid_pkg.sh "cisc_124"; echo $? # 0

is_valid_pkg.sh Util; echo $? # 1

is_valid_pkg.sh 7up; echo $? # 1

is_valid_pkg.sh "cisc 124"; echo $? # 1

answer bash please