Accessing arguments - Step-by-Step Execution

Concept Flow - Accessing arguments

Program starts

↓

main(int argc, char *argv[

↓

Check argc (argument count)

↓

Access argv array elements

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Use arguments in program

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Program ends

The program starts and main receives argc and argv. argc tells how many arguments, argv holds them. The program checks argc, accesses argv elements, then uses them.

Execution Sample

C

#include <stdio.h>

int main(int argc, char *argv[]) {
    for (int i = 0; i < argc; i++) {
        printf("Argument %d: %s\n", i, argv[i]);
    }
    return 0;
}

This code prints all command-line arguments passed to the program, including the program name.

Execution Table

Iteration	i	Condition (i < argc)	Action	Output
1	0	0 < argc (true)	Print argv[0]	Argument 0: ./program
2	1	1 < argc (true)	Print argv[1]	Argument 1: input.txt
3	2	2 < argc (true)	Print argv[2]	Argument 2: 123
4	3	3 < argc (false)	Exit loop

💡 i reaches 3, condition 3 < argc (3) is false, loop ends

Variable Tracker

Variable	Start	After 1	After 2	After 3	Final
i	-	0	1	2	3
argc	3	3	3	3	3
argv[i]	argv[0]	argv[0]	argv[1]	argv[2]	-

Key Moments - 3 Insights

Why does argv[0] contain the program name?

argv[0] always holds the program's name or path, so the first printed argument is the program itself, as shown in execution_table row 1.

What happens if argc is 1?

If argc is 1, it means no extra arguments were passed, so the loop runs once printing only argv[0], the program name, as the condition i < argc is true only for i=0.

Why does the loop stop when i equals argc?

The loop condition is i < argc. When i equals argc, the condition is false, so the loop exits, as shown in execution_table row 4.

Visual Quiz - 3 Questions

Look at the execution_table, what is printed when i = 1?

A Argument 1: ./program

B Argument 1: input.txt

C Argument 1: 123

D No output

💡 Hint

Check execution_table row 2 under Output column.

At which iteration does the loop condition become false?

A Iteration 2

B Iteration 3

C Iteration 4

D Iteration 1

💡 Hint

See execution_table row 4 Condition column.

If argc was 2, how many times would the loop run?

A 2 times

B 3 times

C 1 time

D 0 times

💡 Hint

Loop runs while i < argc, so for argc=2, i=0 and i=1 are valid.

Concept Snapshot

Accessing arguments in C:
- main receives int argc and char *argv[]
- argc = number of arguments including program name
- argv = array of strings with arguments
- argv[0] is program name
- Loop from i=0 to i<argc to access all arguments

Full Transcript

In C, the main function can access command-line arguments using two parameters: argc and argv. argc tells how many arguments were passed, including the program name. argv is an array of strings holding each argument. The program often loops from 0 to argc-1 to print or use each argument. argv[0] is always the program's name or path. The loop stops when the index reaches argc because the condition i < argc becomes false. This way, the program safely accesses all arguments passed to it.