C

Command Line Arguments

C 131 views Dec 22, 2025 1 min read

Command line arguments allow values to be passed to a C program at the time of execution from the command prompt.

main() with Command Line Arguments

int main(int argc, char *argv[])

Explanation

  • argc – Argument count (number of arguments)

  • argv – Argument vector (array of strings)

  • argv[0] – Program name

  • argv[1] onwards – User-supplied arguments

Example Program

#include 

int main(int argc, char *argv[]) {
    int i;

    printf("Number of arguments: %d\n", argc);

    for (i = 0; i < argc>printf("Argument %d: %s\n", i, argv[i]);
    }

    return 0;
}

Sample Execution

program.exe Hello C

Output

Number of arguments: 3
Argument 0: program.exe
Argument 1: Hello
Argument 2: C

Converting Command Line Arguments

  • Arguments are strings

  • Use functions like atoi(), atof()

int num = atoi(argv[1]);

Example (Add Two Numbers)

#include 
#include 

int main(int argc, char *argv[]) {
    int a, b, sum;

    a = atoi(argv[1]);
    b = atoi(argv[2]);

    sum = a + b;
    printf("Sum = %d", sum);

    return 0;
}

Advantages

  • No need for user input during execution

  • Useful in batch processing

  • Flexible program execution

Summary

  • Command line arguments are passed during execution

  • argc stores count, argv stores values

  • Arguments are strings by default

  • Conversion functions are required

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