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

#include <unistd.h>


void usage(const char *name, const char *message)
{
    fprintf(
        stderr,
        "usage: %1$s proxy command [arg [arg [...]]]\n"
        "  the proxy parameter may be set to '-' so no proxy will be used\n"
        "%1$s: %2$s\n",
        name, message
    );
    exit(1);
}

int main(int argc, char **argv, char **env)
{
    if (argc < 2)
        usage(argv[0], "no proxy was specified");
    else if (argc < 3)
        usage(argv[0], "no command was specified");

    for (char **envp = env; *envp != NULL; ++envp)
    {
        *strchr(*envp, '=') = '\0';

        for (char *cp = *envp; *cp != '\0'; ++cp)
            *cp = tolower(*cp);

        if (strstr(*envp, "_proxy"))
            unsetenv(*envp);
    }

    if (strcmp(argv[1], "-"))
        setenv("all_proxy", argv[1], 1);

    return execvp(argv[2], &argv[2]);
}