Command Line Arguments in C

?Why Use Command Line Arguments?

Without command line arguments, your program must ask for input interactively. But what if you want to:

Automate Tasks

Run your program in scripts without manual input:
./process file1.txt file2.txt

⚙️ Configure Behavior

Change program behavior with flags:
./program --verbose --output=result.txt

Build CLI Tools

Create professional tools like gcc, ls, git

Batch Processing

Process multiple files in a loop without recompiling

01What are Command Line Arguments?

Command line arguments allow you to pass data to your program when you run it from the terminal. Instead of asking for input during execution, users can provide values directly when starting the program.

Example Usage

# Without command line arguments

./program

# With command line arguments

./program hello world 123

Real-World Examples

• gcc myfile.c -o myprogram — compiler takes file names as arguments
• ls -la /home — flags and paths as arguments
• cp source.txt dest.txt — copy command takes file names

02Understanding argc and argv

To receive command line arguments, your main() function must use two special parameters:

Memory Visualization: argv Array

Command: ./calc add 5 10

argc = 4→Number of arguments

argv[0]→

"./calc"

Program name

argv[1]→

"add"

First argument

argv[2]→

"5"

Second argument

argv[3]→

"10"

Third argument

argv[4]→

NULL

Terminator

argv[argc] is always NULL — marks end of array

argc (Argument Count)

An int that holds the number of arguments passed, including the program name itself.

./program hello world

argc = 3

argv (Argument Vector)

An array of char* (strings) containing each argument.

./program hello world

argv[0] = "./program"

argv[1] = "hello"

argv[2] = "world"

main_signature.c

1// Standard main() without arguments
2int main(void) {
3    return 0;
4}
5
6// main() with command line arguments
7int main(int argc, char *argv[]) {
8    // argc = argument count
9    // argv = argument vector (array of strings)
10    return 0;
11}
12
13// Alternative syntax (equivalent)
14int main(int argc, char **argv) {
15    return 0;
16}

03Your First Command Line Program

Let's create a simple program that prints all the arguments passed to it:

print_args.c

1#include <stdio.h>
2
3int main(int argc, char *argv[]) {
4    printf("Number of arguments: %d\n", argc);
5    
6    printf("\nAll arguments:\n");
7    for (int i = 0; i < argc; i++) {
8        printf("  argv[%d] = %s\n", i, argv[i]);
9    }
10    
11    return 0;
12}

Output

$ ./print_args hello world 123

Number of arguments: 4

All arguments:

argv[0] = ./print_args

argv[1] = hello

argv[2] = world

argv[3] = 123

Important Notes

• argv[0] is always the program name
• All arguments are strings, even numbers like "123"
• argv[argc] is guaranteed to be NULL

04Converting String Arguments to Numbers

Since all command line arguments are strings, you need to convert them if you want to use them as numbers.

Function	Header	Converts to	Example
atoi()	<stdlib.h>	int	atoi("123") → 123
atol()	<stdlib.h>	long	atol("123456") → 123456L
atof()	<stdlib.h>	double	atof("3.14") → 3.14
strtol()	<stdlib.h>	long	Better error handling

calculator.c

1#include <stdio.h>
2#include <stdlib.h>  // For atoi()
3
4int main(int argc, char *argv[]) {
5    // Check if correct number of arguments
6    if (argc != 4) {
7        printf("Usage: %s <num1> <operator> <num2>\n", argv[0]);
8        printf("Example: %s 10 + 5\n", argv[0]);
9        return 1;
10    }
11    
12    // Convert string arguments to numbers
13    int num1 = atoi(argv[1]);
14    char operator = argv[2][0];  // First character of operator string
15    int num2 = atoi(argv[3]);
16    
17    int result;
18    
19    switch (operator) {
20        case '+': result = num1 + num2; break;
21        case '-': result = num1 - num2; break;
22        case 'x': result = num1 * num2; break;  // Use 'x' for multiply
23        case '/': 
24            if (num2 == 0) {
25                printf("Error: Division by zero!\n");
26                return 1;
27            }
28            result = num1 / num2; 
29            break;
30        default:
31            printf("Unknown operator: %c\n", operator);
32            return 1;
33    }
34    
35    printf("%d %c %d = %d\n", num1, operator, num2, result);
36    return 0;
37}

Output

$ ./calculator 10 + 5

10 + 5 = 15

$ ./calculator 20 - 8

20 - 8 = 12

$ ./calculator 6 x 7

6 x 7 = 42

05Validating Command Line Arguments

Always validate command line arguments! Users might provide wrong inputs, missing arguments, or invalid data.

file_reader.c

1#include <stdio.h>
2#include <stdlib.h>
3
4int main(int argc, char *argv[]) {
5    // Step 1: Check argument count
6    if (argc < 2) {
7        fprintf(stderr, "Error: No filename provided\n");
8        fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
9        return 1;
10    }
11    
12    // Step 2: Try to open the file
13    FILE *file = fopen(argv[1], "r");
14    if (file == NULL) {
15        fprintf(stderr, "Error: Cannot open file '%s'\n", argv[1]);
16        return 1;
17    }
18    
19    // Step 3: Read and display file contents
20    printf("Contents of %s:\n", argv[1]);
21    printf("─────────────────────────\n");
22    
23    char buffer[256];
24    while (fgets(buffer, sizeof(buffer), file) != NULL) {
25        printf("%s", buffer);
26    }
27    
28    fclose(file);
29    return 0;
30}

Best Practices

✓ Always check argc before accessing argv
✓ Provide helpful usage messages when arguments are wrong
✓ Use fprintf(stderr, ...) for error messages
✓ Return non-zero exit code on errors

06Practical Examples

Example 1: Greeting Program

greet.c

1#include <stdio.h>
2
3int main(int argc, char *argv[]) {
4    if (argc == 1) {
5        printf("Hello, World!\n");
6    } else if (argc == 2) {
7        printf("Hello, %s!\n", argv[1]);
8    } else {
9        printf("Hello");
10        for (int i = 1; i < argc; i++) {
11            printf(" %s", argv[i]);
12            if (i < argc - 1) printf(",");
13        }
14        printf("!\n");
15    }
16    return 0;
17}

Outputs

$ ./greet → Hello, World!

$ ./greet Alice → Hello, Alice!

$ ./greet Alice Bob Carol → Hello Alice, Bob, Carol!

Example 2: File Copy Utility

mycopy.c

1#include <stdio.h>
2
3int main(int argc, char *argv[]) {
4    if (argc != 3) {
5        printf("Usage: %s <source> <destination>\n", argv[0]);
6        return 1;
7    }
8    
9    FILE *source = fopen(argv[1], "rb");
10    if (!source) {
11        printf("Error: Cannot open source file '%s'\n", argv[1]);
12        return 1;
13    }
14    
15    FILE *dest = fopen(argv[2], "wb");
16    if (!dest) {
17        printf("Error: Cannot create destination file '%s'\n", argv[2]);
18        fclose(source);
19        return 1;
20    }
21    
22    char buffer[4096];
23    size_t bytes;
24    size_t total = 0;
25    
26    while ((bytes = fread(buffer, 1, sizeof(buffer), source)) > 0) {
27        fwrite(buffer, 1, bytes, dest);
28        total += bytes;
29    }
30    
31    printf("Copied %zu bytes from '%s' to '%s'\n", total, argv[1], argv[2]);
32    
33    fclose(source);
34    fclose(dest);
35    return 0;
36}

07Processing Command Line Flags

Many programs use flags (options starting with -) to modify behavior:

word_count.c

1#include <stdio.h>
2#include <string.h>
3#include <stdbool.h>
4
5int main(int argc, char *argv[]) {
6    bool count_lines = false;
7    bool count_words = false;
8    bool count_chars = false;
9    char *filename = NULL;
10    
11    // Parse command line flags
12    for (int i = 1; i < argc; i++) {
13        if (strcmp(argv[i], "-l") == 0) {
14            count_lines = true;
15        } else if (strcmp(argv[i], "-w") == 0) {
16            count_words = true;
17        } else if (strcmp(argv[i], "-c") == 0) {
18            count_chars = true;
19        } else if (argv[i][0] != '-') {
20            filename = argv[i];
21        }
22    }
23    
24    // Default: count everything
25    if (!count_lines && !count_words && !count_chars) {
26        count_lines = count_words = count_chars = true;
27    }
28    
29    if (!filename) {
30        printf("Usage: %s [-l] [-w] [-c] <filename>\n", argv[0]);
31        printf("  -l  Count lines\n");
32        printf("  -w  Count words\n");
33        printf("  -c  Count characters\n");
34        return 1;
35    }
36    
37    FILE *file = fopen(filename, "r");
38    if (!file) {
39        printf("Error: Cannot open '%s'\n", filename);
40        return 1;
41    }
42    
43    int lines = 0, words = 0, chars = 0;
44    int ch, prev = ' ';
45    
46    while ((ch = fgetc(file)) != EOF) {
47        chars++;
48        if (ch == '\n') lines++;
49        if ((prev == ' ' || prev == '\n' || prev == '\t') && 
50            (ch != ' ' && ch != '\n' && ch != '\t')) {
51            words++;
52        }
53        prev = ch;
54    }
55    
56    // Print requested counts
57    if (count_lines) printf("Lines: %d\n", lines);
58    if (count_words) printf("Words: %d\n", words);
59    if (count_chars) printf("Chars: %d\n", chars);
60    
61    fclose(file);
62    return 0;
63}

Usage Examples

$ ./wc myfile.txt # Count all

$ ./wc -l myfile.txt # Lines only

$ ./wc -w -c myfile.txt # Words and chars

!Code Pitfalls: Common Mistakes & What to Watch For

Common Mistakes with Command Line Arguments

Copying code often generate command line parsing code with dangerous flaws:

✗No argc validation: Beginners often access argv[1] without checking if argc > 1, causing crashes
✗Unsafe atoi() usage: Code often uses atoi() without checking for non-numeric input, producing garbage values
✗Buffer overflow risks: Beginners often copy argv strings into fixed-size buffers without length checks
✗Missing error messages: Beginners often forget to print usage help when arguments are wrong, confusing users

Always Understand Before Using

Test copied argument parsing with: no arguments, too many arguments, wrong types, empty strings, and special characters. Command line args are user input — never trust them! Use strtol() instead of atoi() for proper error handling.

09Frequently Asked Questions

Q:Why is argc always at least 1?

A: The program name itself counts as the first argument (argv[0]). Even running./myprogram with no args gives argc=1 and argv[0]="./myprogram". User arguments start at argv[1].

Q:How do I convert argv strings to numbers?

A: Use conversion functions:atoi(argv[1]) for int,atof(argv[1]) for float. Better: usestrtol() and strtod() which provide error checking. All arguments come as strings!

Q:What is argv[argc]?

A: It's guaranteed to be NULL by the C standard. This lets you loop with while (argv[i] != NULL) instead of checking argc. Useful for iterating all arguments.

Q:How do I handle options like -v or --help?

A: For simple cases, usestrcmp(argv[i], "-v") to check each argument. For complex options, use the getopt() function (POSIX) or getopt_long() for GNU-style long options.

Q:What happens if I use argc but declare int main(void)?

A: If you declare int main(void), argc and argv aren't available. You must useint main(int argc, char *argv[]) to access them. Both signatures are valid C; choose based on whether you need arguments.

09Summary

✓Key Points

• argc = argument count (including program name)
• argv = array of string arguments
• argv[0] = program name
• All arguments are strings — convert with atoi(), etc.
• Always validate before using arguments

Common Uses

• File processing tools
• Calculators and converters
• Automation scripts
• Configuration utilities
• System administration tools

11Argument Parsing Tips

Use getopt() for Complex Arguments

For programs with many options (-v, -h,--verbose), use the standard getopt()function. It handles short and long options, required values, and error reporting.

Print Usage on Error

Always provide a helpful usage message when arguments are wrong. Include the expected format, optional vs required arguments, and examples. This makes your tool user-friendly.

Support Standard Options

Consider supporting common conventions like --help and--version. These are expected by users and make your program feel professional. Return exit code 0 for success, non-zero for errors.

?Why Use Command Line Arguments?

Without command line arguments, your program must ask for input interactively. But what if you want to:

Automate Tasks

Run your program in scripts without manual input:
./process file1.txt file2.txt

⚙️ Configure Behavior

Change program behavior with flags:
./program --verbose --output=result.txt

Build CLI Tools

Create professional tools like gcc, ls, git

Batch Processing

Process multiple files in a loop without recompiling

01What are Command Line Arguments?

Example Usage

# Without command line arguments

./program

# With command line arguments

./program hello world 123

Real-World Examples

• gcc myfile.c -o myprogram — compiler takes file names as arguments
• ls -la /home — flags and paths as arguments
• cp source.txt dest.txt — copy command takes file names

02Understanding argc and argv

To receive command line arguments, your main() function must use two special parameters:

Memory Visualization: argv Array

Command: ./calc add 5 10

argc = 4→Number of arguments

argv[0]→

"./calc"

Program name

argv[1]→

"add"

First argument

argv[2]→

"5"

Second argument

argv[3]→

"10"

Third argument

argv[4]→

NULL

Terminator

argv[argc] is always NULL — marks end of array

argc (Argument Count)

An int that holds the number of arguments passed, including the program name itself.

./program hello world

argc = 3

argv (Argument Vector)

An array of char* (strings) containing each argument.

./program hello world

argv[0] = "./program"

argv[1] = "hello"

argv[2] = "world"

main_signature.c

1// Standard main() without arguments
2int main(void) {
3    return 0;
4}
5
6// main() with command line arguments
7int main(int argc, char *argv[]) {
8    // argc = argument count
9    // argv = argument vector (array of strings)
10    return 0;
11}
12
13// Alternative syntax (equivalent)
14int main(int argc, char **argv) {
15    return 0;
16}

03Your First Command Line Program

Let's create a simple program that prints all the arguments passed to it:

print_args.c

1#include <stdio.h>
2
3int main(int argc, char *argv[]) {
4    printf("Number of arguments: %d\n", argc);
5    
6    printf("\nAll arguments:\n");
7    for (int i = 0; i < argc; i++) {
8        printf("  argv[%d] = %s\n", i, argv[i]);
9    }
10    
11    return 0;
12}

Output

$ ./print_args hello world 123

Number of arguments: 4

All arguments:

argv[0] = ./print_args

argv[1] = hello

argv[2] = world

argv[3] = 123

Important Notes

• argv[0] is always the program name
• All arguments are strings, even numbers like "123"
• argv[argc] is guaranteed to be NULL

04Converting String Arguments to Numbers

Since all command line arguments are strings, you need to convert them if you want to use them as numbers.

Function	Header	Converts to	Example
atoi()	<stdlib.h>	int	atoi("123") → 123
atol()	<stdlib.h>	long	atol("123456") → 123456L
atof()	<stdlib.h>	double	atof("3.14") → 3.14
strtol()	<stdlib.h>	long	Better error handling

calculator.c

1#include <stdio.h>
2#include <stdlib.h>  // For atoi()
3
4int main(int argc, char *argv[]) {
5    // Check if correct number of arguments
6    if (argc != 4) {
7        printf("Usage: %s <num1> <operator> <num2>\n", argv[0]);
8        printf("Example: %s 10 + 5\n", argv[0]);
9        return 1;
10    }
11    
12    // Convert string arguments to numbers
13    int num1 = atoi(argv[1]);
14    char operator = argv[2][0];  // First character of operator string
15    int num2 = atoi(argv[3]);
16    
17    int result;
18    
19    switch (operator) {
20        case '+': result = num1 + num2; break;
21        case '-': result = num1 - num2; break;
22        case 'x': result = num1 * num2; break;  // Use 'x' for multiply
23        case '/': 
24            if (num2 == 0) {
25                printf("Error: Division by zero!\n");
26                return 1;
27            }
28            result = num1 / num2; 
29            break;
30        default:
31            printf("Unknown operator: %c\n", operator);
32            return 1;
33    }
34    
35    printf("%d %c %d = %d\n", num1, operator, num2, result);
36    return 0;
37}

Output

$ ./calculator 10 + 5

10 + 5 = 15

$ ./calculator 20 - 8

20 - 8 = 12

$ ./calculator 6 x 7

6 x 7 = 42

05Validating Command Line Arguments

Always validate command line arguments! Users might provide wrong inputs, missing arguments, or invalid data.

file_reader.c

1#include <stdio.h>
2#include <stdlib.h>
3
4int main(int argc, char *argv[]) {
5    // Step 1: Check argument count
6    if (argc < 2) {
7        fprintf(stderr, "Error: No filename provided\n");
8        fprintf(stderr, "Usage: %s <filename>\n", argv[0]);
9        return 1;
10    }
11    
12    // Step 2: Try to open the file
13    FILE *file = fopen(argv[1], "r");
14    if (file == NULL) {
15        fprintf(stderr, "Error: Cannot open file '%s'\n", argv[1]);
16        return 1;
17    }
18    
19    // Step 3: Read and display file contents
20    printf("Contents of %s:\n", argv[1]);
21    printf("─────────────────────────\n");
22    
23    char buffer[256];
24    while (fgets(buffer, sizeof(buffer), file) != NULL) {
25        printf("%s", buffer);
26    }
27    
28    fclose(file);
29    return 0;
30}

Best Practices

✓ Always check argc before accessing argv
✓ Provide helpful usage messages when arguments are wrong
✓ Use fprintf(stderr, ...) for error messages
✓ Return non-zero exit code on errors

06Practical Examples

Example 1: Greeting Program

greet.c

1#include <stdio.h>
2
3int main(int argc, char *argv[]) {
4    if (argc == 1) {
5        printf("Hello, World!\n");
6    } else if (argc == 2) {
7        printf("Hello, %s!\n", argv[1]);
8    } else {
9        printf("Hello");
10        for (int i = 1; i < argc; i++) {
11            printf(" %s", argv[i]);
12            if (i < argc - 1) printf(",");
13        }
14        printf("!\n");
15    }
16    return 0;
17}

Outputs

$ ./greet → Hello, World!

$ ./greet Alice → Hello, Alice!

$ ./greet Alice Bob Carol → Hello Alice, Bob, Carol!

Example 2: File Copy Utility

mycopy.c

1#include <stdio.h>
2
3int main(int argc, char *argv[]) {
4    if (argc != 3) {
5        printf("Usage: %s <source> <destination>\n", argv[0]);
6        return 1;
7    }
8    
9    FILE *source = fopen(argv[1], "rb");
10    if (!source) {
11        printf("Error: Cannot open source file '%s'\n", argv[1]);
12        return 1;
13    }
14    
15    FILE *dest = fopen(argv[2], "wb");
16    if (!dest) {
17        printf("Error: Cannot create destination file '%s'\n", argv[2]);
18        fclose(source);
19        return 1;
20    }
21    
22    char buffer[4096];
23    size_t bytes;
24    size_t total = 0;
25    
26    while ((bytes = fread(buffer, 1, sizeof(buffer), source)) > 0) {
27        fwrite(buffer, 1, bytes, dest);
28        total += bytes;
29    }
30    
31    printf("Copied %zu bytes from '%s' to '%s'\n", total, argv[1], argv[2]);
32    
33    fclose(source);
34    fclose(dest);
35    return 0;
36}

07Processing Command Line Flags

Many programs use flags (options starting with -) to modify behavior:

word_count.c

1#include <stdio.h>
2#include <string.h>
3#include <stdbool.h>
4
5int main(int argc, char *argv[]) {
6    bool count_lines = false;
7    bool count_words = false;
8    bool count_chars = false;
9    char *filename = NULL;
10    
11    // Parse command line flags
12    for (int i = 1; i < argc; i++) {
13        if (strcmp(argv[i], "-l") == 0) {
14            count_lines = true;
15        } else if (strcmp(argv[i], "-w") == 0) {
16            count_words = true;
17        } else if (strcmp(argv[i], "-c") == 0) {
18            count_chars = true;
19        } else if (argv[i][0] != '-') {
20            filename = argv[i];
21        }
22    }
23    
24    // Default: count everything
25    if (!count_lines && !count_words && !count_chars) {
26        count_lines = count_words = count_chars = true;
27    }
28    
29    if (!filename) {
30        printf("Usage: %s [-l] [-w] [-c] <filename>\n", argv[0]);
31        printf("  -l  Count lines\n");
32        printf("  -w  Count words\n");
33        printf("  -c  Count characters\n");
34        return 1;
35    }
36    
37    FILE *file = fopen(filename, "r");
38    if (!file) {
39        printf("Error: Cannot open '%s'\n", filename);
40        return 1;
41    }
42    
43    int lines = 0, words = 0, chars = 0;
44    int ch, prev = ' ';
45    
46    while ((ch = fgetc(file)) != EOF) {
47        chars++;
48        if (ch == '\n') lines++;
49        if ((prev == ' ' || prev == '\n' || prev == '\t') && 
50            (ch != ' ' && ch != '\n' && ch != '\t')) {
51            words++;
52        }
53        prev = ch;
54    }
55    
56    // Print requested counts
57    if (count_lines) printf("Lines: %d\n", lines);
58    if (count_words) printf("Words: %d\n", words);
59    if (count_chars) printf("Chars: %d\n", chars);
60    
61    fclose(file);
62    return 0;
63}

Usage Examples

$ ./wc myfile.txt # Count all

$ ./wc -l myfile.txt # Lines only

$ ./wc -w -c myfile.txt # Words and chars

!Code Pitfalls: Common Mistakes & What to Watch For

Common Mistakes with Command Line Arguments

Copying code often generate command line parsing code with dangerous flaws:

✗No argc validation: Beginners often access argv[1] without checking if argc > 1, causing crashes
✗Unsafe atoi() usage: Code often uses atoi() without checking for non-numeric input, producing garbage values
✗Buffer overflow risks: Beginners often copy argv strings into fixed-size buffers without length checks
✗Missing error messages: Beginners often forget to print usage help when arguments are wrong, confusing users

Always Understand Before Using

09Frequently Asked Questions

Q:Why is argc always at least 1?

A: The program name itself counts as the first argument (argv[0]). Even running./myprogram with no args gives argc=1 and argv[0]="./myprogram". User arguments start at argv[1].

Q:How do I convert argv strings to numbers?

A: Use conversion functions:atoi(argv[1]) for int,atof(argv[1]) for float. Better: usestrtol() and strtod() which provide error checking. All arguments come as strings!

Q:What is argv[argc]?

A: It's guaranteed to be NULL by the C standard. This lets you loop with while (argv[i] != NULL) instead of checking argc. Useful for iterating all arguments.

Q:How do I handle options like -v or --help?

A: For simple cases, usestrcmp(argv[i], "-v") to check each argument. For complex options, use the getopt() function (POSIX) or getopt_long() for GNU-style long options.

Q:What happens if I use argc but declare int main(void)?

09Summary

✓Key Points

• argc = argument count (including program name)
• argv = array of string arguments
• argv[0] = program name
• All arguments are strings — convert with atoi(), etc.
• Always validate before using arguments

Common Uses

• File processing tools
• Calculators and converters
• Automation scripts
• Configuration utilities
• System administration tools

11Argument Parsing Tips

Use getopt() for Complex Arguments

For programs with many options (-v, -h,--verbose), use the standard getopt()function. It handles short and long options, required values, and error reporting.

Print Usage on Error

Always provide a helpful usage message when arguments are wrong. Include the expected format, optional vs required arguments, and examples. This makes your tool user-friendly.

Support Standard Options

Consider supporting common conventions like --help and--version. These are expected by users and make your program feel professional. Return exit code 0 for success, non-zero for errors.

What You Will Learn

?Why Use Command Line Arguments?

Automate Tasks

⚙️ Configure Behavior

Build CLI Tools

Batch Processing

01What are Command Line Arguments?

Example Usage

Real-World Examples

02Understanding argc and argv

Memory Visualization: argv Array

argc (Argument Count)

argv (Argument Vector)

03Your First Command Line Program

Output

Important Notes

04Converting String Arguments to Numbers

Output

05Validating Command Line Arguments

Best Practices

06Practical Examples

Example 1: Greeting Program

Outputs

Example 2: File Copy Utility

07Processing Command Line Flags

Usage Examples

!Code Pitfalls: Common Mistakes & What to Watch For

Common Mistakes with Command Line Arguments

Always Understand Before Using

09Frequently Asked Questions

Q:Why is argc always at least 1?

Q:How do I convert argv strings to numbers?

Q:What is argv[argc]?

Q:How do I handle options like -v or --help?

Q:What happens if I use argc but declare int main(void)?

09Summary

✓Key Points

Common Uses

11Argument Parsing Tips

Use getopt() for Complex Arguments

Print Usage on Error

Support Standard Options

Test Your Knowledge

Related Tutorials

Functions in C

Graphics Programming with graphics.h

Multi-File Programs in C

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What You Will Learn

?Why Use Command Line Arguments?

Automate Tasks

⚙️ Configure Behavior

Build CLI Tools

Batch Processing

01What are Command Line Arguments?

Example Usage

Real-World Examples

02Understanding argc and argv

Memory Visualization: argv Array

argc (Argument Count)

argv (Argument Vector)

03Your First Command Line Program

Output

Important Notes

04Converting String Arguments to Numbers

Output

05Validating Command Line Arguments

Best Practices

06Practical Examples

Example 1: Greeting Program

Outputs

Example 2: File Copy Utility

07Processing Command Line Flags

Usage Examples

!Code Pitfalls: Common Mistakes & What to Watch For

Common Mistakes with Command Line Arguments

Always Understand Before Using

09Frequently Asked Questions

Q:Why is argc always at least 1?

Q:How do I convert argv strings to numbers?