3.3 Turning Commands into a Script (weight: 4) LINUX-ESSENTIALS Practice Questions (Page 5)

Questions 21–25

1. 21expert · medium

   A senior admin is debugging a script that processes user input. The script uses 'set -x' at the top. When running the script with an argument 'foo', the trace shows: '+ [ foo = bar ]' and then the script takes the else branch. The admin expected the if branch. What is the most likely issue?

   • AThe script is comparing the argument to 'bar' instead of 'foo'.
   • BThe variable being compared is not the script argument but a different variable.
   • CThe script is missing a shebang, so the trace is unreliable.
   • DThe test uses single brackets instead of double brackets.
   Reveal Solution Discussion Select an answer first
2. 22expert · hard

   A script must check if a file exists and is readable, and if so, print its contents. The admin writes: 'if [ -r file.txt ]; then cat file.txt; fi'. However, the script prints nothing even though the file exists and is readable. What is the most likely cause?

   • AThe script is missing a shebang, so the test is not executed.
   • BThe file is a directory, and cat fails on directories.
   • CThe script is running with a different user that does not have read permission.
   • DThe file is a symbolic link to a non-existent target.
   Reveal Solution Discussion Select an answer first
4. 23expert · medium

   A script needs to process a list of usernames from a file, one per line. The admin uses 'for user in $(cat users.txt); do ...'. The script fails when a username contains a space. What is the best fix?

   • AUse 'for user in $(cat users.txt | tr " " "_"); do'
   • BUse 'for user in $(cat users.txt); do' and set IFS to newline.
   • CUse 'for user in "$(cat users.txt)"; do'
   • DUse a while read loop: 'while IFS= read -r user; do ...; done < users.txt'
   Reveal Solution Discussion Select an answer first
5. 24expert · hard

   A script runs a command that may fail, and the admin wants to exit the script with a specific error code if it fails. The admin writes: 'command || exit 1'. However, the script continues even when the command fails. What is the likely reason?

   • AThe exit command is not available in the script's shell.
   • BThe command returns a non-zero exit status but the script ignores it.
   • CThe command is part of a pipeline, and the exit status of the pipeline is the last command's status.
   • DThe script is missing a shebang, so the || operator is not supported.
   Reveal Solution Discussion Select an answer first
6. 25expert · medium

   A script needs to iterate over a list of numbers from 1 to 10 and print the square of each. The admin writes: 'for i in {1..10}; do echo $((i*i)); done'. The script works, but the admin wants to make the upper limit configurable via a variable. Which approach is correct?

   • Afor i in $(seq 1 $limit); do echo $((i*i)); done
   • Bfor i in {1..$limit}; do echo $((i*i)); done
   • Dfor i in $(eval echo {1..$limit}); do echo $((i*i)); done
   Reveal Solution Discussion Select an answer first