You want to create a bash script that prints the value of variable user followed by the string _backup only if user is not empty. Which is the best way to write the echo command?

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Bash Scripting - Variables

You want to create a bash script that prints the value of variable user followed by the string _backup only if user is not empty. Which is the best way to write the echo command?

Aecho "${user:+${user}_backup}"

Becho "${user}_backup"

Cecho "${user}_backup" && [ -n "$user" ]

Decho "$user_backup"

Step-by-Step Solution

Solution:

Step 1: Understand conditional variable expansion
The expression ${user:+${user}_backup} prints ${user}_backup only if user is not empty.
Step 2: Compare options
echo "${user}_backup" always prints _backup even if user is empty. echo "$user_backup" looks for variable user_backup. echo "${user}_backup" && [ -n "$user" ] has wrong syntax mixing echo and condition.
Final Answer:
echo "${user:+${user}_backup}" -> Option A
Quick Check:
Use ${var:+value} to print only if var set = B [OK]

Quick Trick: Use ${var:+value} to print only if var is set [OK]

Common Mistakes:

MISTAKES

Using $user_backup instead of ${user}_backup
Printing _backup even if user empty
Mixing echo with condition incorrectly

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More Bash Scripting Quizzes

You want to create a bash script that prints the value of variable user followed by the string _backup only if user is not empty. Which is the best way to write the echo command?

Step 1: Understand conditional variable expansion

Step 2: Compare options

Final Answer:

Quick Check:

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