Which of the following commands should replace the <CONDITIONAL> string?

A user is asking the systems administrator for assistance with writing a script to verify whether a file exists. Given the following:

Which of the following commands should replace the <CONDITIONAL> string?
A . if [ -f "$filename" ]; then
B . if [ -d "$filename" ]; then
C . if [ -f "$filename" ] then
D . if [ -f "$filename" ]; while

View Answer

Answer: A

Explanation:

The command if [ -f "$filename" ]; then checks if the variable $filename refers to a regular file that exists. The -f option is used to test for files. If the condition is true, the commands after then are executed. This is the correct way to replace the <CONDITIONAL> string. The other options are incorrect because they either use the wrong option (-d tests for directories), the wrong syntax (missing a semicolon after the condition), or the wrong keyword (while is used for loops, not conditions).

Reference: CompTIA Linux+ (XK0-005) Certification Study Guide, Chapter 16: Writing and Executing Bash Shell Scripts, page 493.