Namerefs

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Lab

This is the original contents of the lab file (../labs/02-namerefs/02-namerefs.lab.sh).

Follow the instructions in the file to solve the lab.

sobash_assert_nameref_variable_is_not_empty() {

  # The "-n" option of the "local" builtin acts similar a "pointer" in C
  # Rather than expecting a string and storing a string,
  # it expects the name of another variable,
  # and it "points to" the value of that variable without restoring it.
  # In Bash, this is called a "name reference" to another variable.
  local -n variable_value
  local variable_name

  # Based on your understanding of name references,
  # what goes in place of "$_" below to make the "if" statement return 0?
  variable_value="$_"
  variable_name="$1"

  if [[ "$variable_value" == "" ]]; then
    echo -e "\n[FAIL] Variable ($variable_name) is empty." 1>&2
    return 2
  else
    echo -e "\n[INFO] Variable ($variable_name) is not empty."
    return 0
  fi

}

# What line is missing from this function to make it work as intended?
# Hint: this function does the opposite of the one above it, but works similarly.
sobash_assert_nameref_variable_is_empty() {

  local -n variable_value
  local variable_name

  variable_name="$1"

  if [[ "$variable_value" != "" ]]; then
    echo -e "\n[INFO] Variable ($variable_name) is not empty." 1>&2
    return 2
  else
    echo -e "\n[INFO] Variable ($variable_name) is empty."
    return 0
  fi

}

Test

This is the original contents of the test file (../labs/02-namerefs/02-namerefs.test.sh).

Review the test cases and your lab file.

Will the lab file (../labs/02-namerefs/02-namerefs.lab.sh) pass all test cases?

#!/usr/bin/env bash

test_assert_nameref_variable_is_not_empty() {

   declare MY_NOT_EMPTY_VARIABLE
   MY_NOT_EMPTY_VARIABLE="this variable has a value"
   export MY_NOT_EMPTY_VARIABLE
   ../build/sobash assert-nameref-variable-is-not-empty MY_NOT_EMPTY_VARIABLE
   assertEquals 0 $?

}


test_assert_nameref_variable_is_empty() {

   declare MY_EMPTY_VARIABLE
   MY_EMPTY_VARIABLE=""
   export MY_EMPTY_VARIABLE
   ../build/sobash assert-nameref-variable-is-empty MY_EMPTY_VARIABLE
   assertEquals 0 $?

}

source ./shunit2

When ready, run the following to execute the tests above against the lab file:

cd "${HOME}/bash-programming/src/" \ 
  && ./test.sh lab 02-namerefs

Solution

This is the original contents of the solution file (../labs/02-namerefs/02-namerefs.solution.sh).

This file contains an example of a viable solution that passes all the test cases.

sobash_assert_nameref_variable_is_not_empty() {

  local -n variable_value
  local variable_name

  variable_value="$1"
  variable_name="$1"

  if [[ "$variable_value" == "" ]]; then
    echo -e "\n[FAIL] ${FUNCNAME[0]} | Variable ($variable_name) is empty." 1>&2
    return 2
  else
    echo -e "\n[INFO] ${FUNCNAME[0]} | Variable ($variable_name) is not empty."
    return 0
  fi

}


sobash_assert_nameref_variable_is_empty() {

  local -n variable_value
  local variable_name

  variable_value="$1"
  variable_name="$1"

  if [[ "$variable_value" != "" ]]; then
    echo -e "\n[INFO] ${FUNCNAME[0]} | Variable ($variable_name) is not empty." 1>&2
    return 2
  else
    echo -e "\n[INFO] ${FUNCNAME[0]} | Variable ($variable_name) is empty."
    return 0
  fi

}

Run the following to execute the tests above against the solution file:

cd "${HOME}/bash-programming/src/" \ 
  && ./test.sh solution 02-namerefs

Feel free to run the following to override the contents of the lab file with the solution file.

cd "${HOME}/bash-programming/labs/" \ 
  && cp ./02-namerefs/02-namerefs.{solution,lab}.sh