Accessing arguments - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are argc and argv in a C program's main function?

argc is the count of command-line arguments passed to the program, including the program name itself. argv is an array of strings (character pointers) holding each argument.

beginner

How do you access the first command-line argument (not the program name) in C?

You access it using argv[1]. argv[0] is the program name, so the first user argument is at index 1.

intermediate

What happens if you try to access argv elements beyond argc - 1?

Accessing beyond argc - 1 leads to undefined behavior because those elements do not exist. It can cause crashes or garbage data.

beginner

How can you convert a command-line argument string to an integer in C?

Use the atoi() function from stdlib.h. For example, int x = atoi(argv[1]); converts the first argument to an integer.

beginner

Why is it important to check argc before accessing argv elements?

Because if you access argv elements without checking argc, you might read invalid memory if the argument was not provided, causing errors.

What does argc represent in a C program?

A Array of command-line arguments

B Number of command-line arguments including program name

C Pointer to the first argument

D Length of the first argument string

argc counts how many arguments were passed, including the program name.

How do you access the program's name from the arguments?

A argv[0]

B argc

C argv[1]

D argv[argc]

The program name is stored at argv[0].

Which header file is needed to use atoi()?

A <string.h>

B <stdio.h>

C <stdlib.h>

D <ctype.h>

atoi() is declared in stdlib.h.

What is the risk of accessing argv[3] when argc is 2?

A No risk, safe to access

B Returns empty string

C Returns NULL safely

D Undefined behavior, may crash

Accessing beyond argc - 1 is unsafe and can cause crashes.

If you want to print all command-line arguments, which loop is correct?

A for (int i = 0; i < argc; i++) printf("%s\n", argv[i]);

B for (int i = 1; i <= argc; i++) printf("%s\n", argv[i]);

C for (int i = 0; i <= argc; i++) printf("%s\n", argv[i]);

D for (int i = 1; i < argc; i++) printf("%s\n", argv[i]);

Looping from 0 to argc - 1 prints all arguments including program name.

Explain how to safely access command-line arguments in a C program.

Think about how to avoid accessing invalid memory.

Describe the role of argv[0] and how it differs from other arguments.

What does the first element in argv usually hold?