Unix - Shell Programming

These flashcards cover key concepts and commands related to Unix Shell Programming, including comments, variable handling, conditional statements, loops, and command line parameters.

What is a comment in a shell script indicated by?

A comment is indicated by the # symbol.

What does the command 'echo "hello world!"' do in a shell script?

It outputs the text 'hello world!' to the terminal.

How do you make a shell script executable and run it as a program?

You use the command 'chmod +x scriptName.sh' followed by './scriptName.sh'.

What is the purpose of return values in shell programming?

Return values indicate the success or failure of a program's execution, with 0 signifying success and 1 signifying failure.

How do you set a variable in shell scripting?

Variables are set using the = operation, for example 'var=value'.

What symbol is used to access the value of a variable in shell scripts?

The dollar sign ($) is used to access the value of a variable.

What is the difference between using $ and {} in variable substitution?

Using {} helps to clarify variable boundaries when concatenating, e.g., '${Color}Sky' versus '$ColorSky'.

How do you read user input into variables in a shell script?

You use the 'read' command followed by variable names, e.g., 'read var1 var2'.

What special variables allow access to command line parameters in shell scripts?

$0 (script name), $1-$9 (first nine arguments), $* (all arguments), and $# (total number of arguments).

How are arithmetic operations performed in shell scripting?

Using the syntax $((expression)), for example, $((1 + 6)).

What command is used for conditional statements in shell scripts?

The 'test' command is used to evaluate expressions.

What does the syntax 'if [ CONDITION ]; then' signify in a shell script?

It signifies the start of a conditional statement that executes if CONDITION evaluates to true.

What is the purpose of the 'case' statement in shell scripting?

It allows for multi-way branching based on the value of a variable.

What is a 'for' loop syntax in shell programming?

'for VAR in LIST; do STATEMENTS; done' is the syntax for a for loop.

What does the 'until' loop do in shell programming?

It repeatedly executes STATEMENTS until the CONDITION is true.