realReplace.c

/* -*- c-file-style: "linux" -*- */
#include <errno.h>
#include <stdio.h>
#include <sys/stat.h>
#include <unistd.h>

int main(int argc, const char *const argv[])
{
        struct stat statbuf;
        if (argc < 2)
        {
                fprintf(stderr, "Usage: %s source dest [backup]", argv[0]);
                return 1;
        }
        if (argc > 3)
        {
                if (unlink(argv[3]))
                {
                        if (errno != ENOENT)
                        {
                                perror("unlink");
                                return 1;
                        }
                }
                if (link(argv[2], argv[3]))
                {
                        perror("link");
                        return 1;
                }
        }
        else
        {
                if (stat(argv[2], &statbuf))
                {
                        perror("stat");
                        return 1;
                }
        }
        if (rename(argv[1], argv[2]))
        {
                perror("rename");
                return 1;
        }
        return 0;
}