fac 0.2.0

build tool
Documentation 
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#include "environ.h"

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

extern char **environ;

static int cmpstr(const void *p1, const void *p2) {
  return strcmp(* (char * const *) p1, * (char * const *) p2);
}

static const char *ignore_these[] = {
  "COLORTERM=",
  "DBUS_SESSION_BUS_ADDRESS=",
  "DESKTOP_SESSION=",
  "DESKTOP_STARTUP_ID=",
  "DISPLAY=",
  "GCONF_GLOBAL_LOCKS=",
  "GDM_LANG=",
  "GDMSESSION=",
  "GIO_LAUNCHED_DESKTOP_FILE_PID=",
  "GIO_LAUNCHED_DESKTOP_FILE=",
  "GJS_DEBUG_OUTPUT=",
  "GJS_DEBUG_TOPICS=",
  "GNOME_DESKTOP_SESSION_ID=",
  "GNOME_KEYRING_CONTROL=",
  "GNOME_KEYRING_PID=",
  "GPG_AGENT_INFO=",
  "OLDPWD=",
  "MAIL=",
  "NCURSES_",
  "PS1=",
  "PWD=",
  "SESSION_MANAGER=",
  "SHLVL=",
  "SSH_AGENT_PID=",
  "SSH_AUTH_SOCK=",
  "SSH_CLIENT=",
  "SSH_CONNECTION=",
  "SSH_TTY=",
  "TERM=",
  "USERNAME=", // not sure why, but this is sporadically defined
  "VTE_VERSION=",
  "WINDOWID=",
  "WINDOWPATH=",
  "XAUTHORITY=",
  "XDG_CURRENT_DESKTOP=",
  "XDG_DATA_DIRS=",
  "XDG_MENU_PREFIX=",
  "XDG_SEAT=",
  "XDG_SESSION_COOKIE=",
  "XDG_SESSION_DESKTOP=",
  "XDG_SESSION_ID=",
  "XDG_VTNR=",
  "_=",
  NULL
};

sha1hash hash_environment(void) {
  bool done_removing = true;
  do {
    const char **to_ignore = &ignore_these[0];
    while (*to_ignore) {
      char **e = environ;
      while (*e) {
        if (!strncmp(*to_ignore, *e, strlen(*to_ignore))) {
          /* delete this environment variable */
          while ((*e = *(e+1))) e++;
          break;
        }
        e++;
      }
      to_ignore++;
    }
  } while (!done_removing);

  sha1nfo sh;
  sha1_init(&sh);
  size_t num_env = 0; /* count environment variables */
  for (num_env = 0;environ[num_env];num_env++);
  /* sort the environment variables, so we will get a reproducible
     hash */
  qsort(environ, num_env, sizeof(char *), cmpstr);
  for (int i=0;i<num_env;i++) {
    sha1_write(&sh, environ[i], strlen(environ[i])+1);
    if (false) printf("env: %s\n", environ[i]); /* uncomment for debugging */
  }
  return sha1_out(&sh);
}