3.3 Turning Commands into a Script (weight: 4) LINUX-ESSENTIALS Practice Questions (Page 6)

Questions 26–30

1. 26expert · hard

   A script is written with a shebang '#!/bin/bash' and saved with execute permissions. When run directly, it works. However, when run with 'sh script.sh', it fails with a syntax error. What is the most likely reason?

   • AThe shebang line is incorrect.
   • BThe script uses bash-specific features not available in sh.
   • CThe script is missing execute permissions for the sh command.
   • DThe script has a Windows line ending.
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2. 27expert · medium

   A script must check if a number is greater than 10 and less than 20. The admin writes: 'if [ $num -gt 10 -a $num -lt 20 ]; then ...'. The script works, but the admin wants to make it more readable and portable. Which alternative is best?

   • Aif test $num -gt 10 -a $num -lt 20; then ...
   • Bif [ $num -gt 10 -o $num -lt 20 ]; then ...
   • Cif [ $num -gt 10 ] && [ $num -lt 20 ]; then ...
   • Dif [[ $num -gt 10 && $num -lt 20 ]]; then ...
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4. 28expert · hard

   A script sets a variable 'MYVAR' and then uses it in a command. The script works when run manually, but when run from cron, the variable is empty. What is the most likely cause?

   • AThe variable is not exported, so it is not available to child processes.
   • BThe script uses command substitution that fails in cron.
   • CThe script is missing a shebang, so cron runs it with a different shell.
   • DThe script relies on an environment variable that is not set in cron's minimal environment.
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5. 29application · easy

   A system administrator writes a script that needs to store the current date in a variable named 'TODAY' and then use it to create a backup directory. The script currently has the line 'TODAY=date'. When run, the variable contains the literal string 'date' instead of the actual date. Which change should the admin make?

   • AChange the line to 'TODAY=`date`'
   • BChange the line to 'TODAY=${date}'
   • CChange the line to 'TODAY=$(date)'
   • DChange the line to 'TODAY="date"'
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6. 30application · medium

   A DevOps engineer writes a script that checks if a configuration file exists before proceeding. The script uses 'if [ -f /etc/app.conf ]; then' but the file is actually a directory. The script incorrectly proceeds. What is the most likely reason?

   • AThe -f test returns true for any path that exists, including directories.
   • BThe -f test returns true for directories as well as regular files.
   • CThe -f test checks for existence, not file type.
   • DThe script lacks a shebang line, so the test is ignored.
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