C: how to use command line arguments

args.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

int main(int argc, char *argv[])
{
    if (argc < 1)
        return 0;

    int i;
    size_t len = 0;
    for (i = 1; i < argc; i++)
    {
        len += strlen(argv[i]);
        if (argc > i + 1)
            len++;
    }

    printf("length: %d\n", len);

    char *cmd;
    cmd = malloc(len);
    cmd[0] = '\0';

    for (i = 1; i < argc; i++)
    {
        strcat(cmd, argv[i]);
        if (argc > i + 1)
            strcat(cmd, " ");
    }
    free(cmd);
    return 0;
}