Shell Scripting Flashcards

In bash, which operator tests whether a string is non-empty?

Answer: [ -n "$var" ]

`-n` returns true if the string length is nonzero; `-z` tests for empty string.

What will `echo ${#myvar}` print if `myvar="hello"`?

Answer: 5

`${#varname}` expands to the length (number of characters) of the variable's value.

Which line should appear at the very top of a bash script to specify the interpreter?

Answer: #!/bin/bash

The shebang `#!/bin/bash` tells the kernel which interpreter to use when the script is executed directly.

How do you pass the value of variable `name` to a script as its first argument and access it inside?

Answer: ./script.sh "$name"; access as $1

Arguments are passed on the command line and accessed inside the script as positional parameters `$1`, `$2`, etc.

What is the effect of `trap 'rm -f /tmp/tmpfile' EXIT` in a script?

Answer: Runs the cleanup command whenever the script exits for any reason

`trap CMD EXIT` registers a command to run automatically whenever the script exits, enabling reliable cleanup.

Which bash feature allows `case "$var" in pattern) ... esac` to match multiple patterns?

Answer: Separate them with |

In a `case` statement, the `|` character separates alternative patterns for the same block.

What does `read -r line` do differently from `read line` in bash?

Answer: Prevents backslash from being treated as an escape character

The `-r` flag disables backslash interpretation, so backslashes are read literally — essential for reading file paths.