change_process_name.c

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

#define  NGX_OK          0
#define  NGX_ERROR      -1
#define NGX_SETPROCTITLE_PAD       '\0'

typedef int                 ngx_int_t;
typedef unsigned int        ngx_uint_t;

extern char **environ;

static char *ngx_os_argv_last;

static int  ngx_argc;
static char **ngx_os_argv;


static u_char *ngx_cpystrn(u_char *dst, const u_char *src, size_t n) {
    if (n == 0) {
        return dst;
    }

    while (--n) {
        *dst = *src;

        if (*dst == '\0') {
            return dst;
        }

        dst++;
        src++;
    }

    *dst = '\0';

    return dst;
}


static void ngx_init_setproctitle() {
    u_char      *p;
    size_t       size;
    ngx_uint_t   i;

    size = 0;

    for (i = 0; environ[i]; i++) {
        size += strlen(environ[i]) + 1;
    }

    p = (u_char *) malloc(size);

    ngx_os_argv_last = ngx_os_argv[0];

    for (i = 0; ngx_os_argv[i]; i++) {
        if (ngx_os_argv_last == ngx_os_argv[i]) {
            ngx_os_argv_last = ngx_os_argv[i] + strlen(ngx_os_argv[i]) + 1;
        }
    }

    for (i = 0; environ[i]; i++) {
        if (ngx_os_argv_last == environ[i]) {

            size = strlen(environ[i]) + 1;
            ngx_os_argv_last = environ[i] + size;

            ngx_cpystrn(p, (u_char *) environ[i], size);
            environ[i] = (char *) p;
            p += size;
        }
    }

    ngx_os_argv_last--;
}


static void ngx_setproctitle(const char *title) {
    u_char     *p;

    ngx_os_argv[1] = NULL;

    p = ngx_cpystrn((u_char *) ngx_os_argv[0], (u_char *) "",
                    ngx_os_argv_last - ngx_os_argv[0]);

    p = ngx_cpystrn(p, (const u_char *) title, ngx_os_argv_last - (char *) p);

    if (ngx_os_argv_last - (char *) p) {
        memset(p, NGX_SETPROCTITLE_PAD, ngx_os_argv_last - (char *) p);
    }

}


void change_process_name(int argc, char *argv[], const char *new_name) {
    ngx_os_argv = argv;
    ngx_argc = argc;
    ngx_init_setproctitle();
    ngx_setproctitle(new_name);
}