Unix - Shell Programming

These flashcards cover key concepts from the Unix Shell Programming lecture, focusing on shell syntax, commands, and control flow.

What is the first line to specify which shell to use in a shell script?

!/bin/bash or #!/usr/bin/perl.

What symbol is used to denote a comment in a shell script?

.

What does the variable $0 represent in shell scripting?

The name of the running program.

How do you perform arithmetic in shell scripting?

Using $(( )) with expressions.

What does a return value of 0 indicate in shell programming?

Success or True.

What is the significance of using single quotes in shell scripting?

Single quotes do not interpret any variables.

What command is used to read user input into variables in shell scripting?

read var1 var2 …

What keyword starts a conditional block in shell scripting?

if.

How is a for loop structured in shell scripting?

for VAR in LIST; do; STATEMENTS; done.

What does the expression [ -x filename ] check in a shell script?

It checks if the filename is executable.

What does the until loop do in shell scripting?

It executes statements until a specified condition is true.

What does the special variable $# represent?

The total number of command line arguments.

What is the function of the test command in shell scripting?

To check if certain conditions are true.

What is the structure of the 'if-else' statement in shell scripting?

if [ CONDITION ]; then; STATEMENTS-YES; else; STATEMENTS-NO; fi.

What type of quotes interpret variables in shell scripting?

Double quotes (" ").

In a for loop, what does the 'do' keyword signify?

It marks the beginning of the statements that will be executed for each item in the list.

What does the expression test ! -x tFile do?

It checks if tFile is not executable.

What should you do if you want to perform commands based on whether conditions are true in shell scripting?

Use control flow statements like 'if' and 'case'.

What are command line parameters and how are they accessed in shell scripts?

Parameters given at execution and accessed via special variables like $1, $2, etc.

What does the command expr do in shell scripting?

It evaluates expressions, often used for arithmetic operations.

What are the three types of loops discussed in shell scripts?

For loop, While loop, Until loop.