cleanup environment variable handling + unit tests

  * removed a putenv() implementation which isn't needed anymore
  * mch_getenv() and mch_setenv() are now functions in src/os/env.c
  * removes direct calls to getenv() and setenv() outside of src/os/env.c
  * refactored the logic of get_env_name into mch_getenvname_at_index
  * added unittests for the functions in os/env.c

16 files changed, 207 insertions, 250 deletions

diff --git a/src/diff.c b/src/diff.c
index ff375c9296..f59ba8015a 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -737,7 +737,7 @@ static void diff_file(char_u *tmp_orig, char_u *tmp_new, char_u *tmp_diff)
     cmd = alloc((unsigned)len);
     if (cmd != NULL) {
       /* We don't want $DIFF_OPTIONS to get in the way. */
-      if (getenv("DIFF_OPTIONS"))
+      if (mch_getenv("DIFF_OPTIONS"))
         vim_setenv((char_u *)"DIFF_OPTIONS", (char_u *)"");
 
       /* Build the diff command and execute it.  Always use -a, binary
diff --git a/src/eval.c b/src/eval.c
index cfcf4ce712..9630976056 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -8552,7 +8552,7 @@ static void f_exists(typval_T *argvars, typval_T *rettv)
   p = get_tv_string(&argvars[0]);
   if (*p == '$') {                      /* environment variable */
     /* first try "normal" environment variables (fast) */
-    if (mch_getenv(p + 1) != NULL)
+    if (mch_getenv((char *)(p + 1)) != NULL)
       n = TRUE;
     else {
       /* try expanding things like $VIM and ${HOME} */
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index f08aab0300..e005472695 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -3322,11 +3322,11 @@ static char_u *get_mess_env(void);
 static char_u *get_mess_env(void)                     {
   char_u      *p;
 
-  p = mch_getenv((char_u *)"LC_ALL");
+  p = (char_u *)mch_getenv("LC_ALL");
   if (p == NULL || *p == NUL) {
-    p = mch_getenv((char_u *)"LC_MESSAGES");
+    p = (char_u *)mch_getenv("LC_MESSAGES");
     if (p == NULL || *p == NUL) {
-      p = mch_getenv((char_u *)"LANG");
+      p = (char_u *)mch_getenv("LANG");
       if (p != NULL && VIM_ISDIGIT(*p))
         p = NULL;                       /* ignore something like "1043" */
 # ifdef HAVE_GET_LOCALE_VAL
diff --git a/src/hangulin.c b/src/hangulin.c
index 4f84312cad..74972d23e2 100644
--- a/src/hangulin.c
+++ b/src/hangulin.c
@@ -14,6 +14,7 @@
 #include "screen.h"
 #include "term.h"
 #include "ui.h"
+#include "os/os.h"
 
 #ifndef HANGUL_DEFAULT_KEYBOARD
 # define HANGUL_DEFAULT_KEYBOARD 3
@@ -653,12 +654,12 @@ static int hangul_automata3(char_u *buf, int_u *c)
 
 void hangul_keyboard_set(void)          {
   int keyboard;
-  char    *s;
+  const char *s;
 
   hangul_input_clear();
 
-  if ((s = getenv("VIM_KEYBOARD")) == NULL)
-    s = getenv("HANGUL_KEYBOARD_TYPE");
+  if ((s = mch_getenv("VIM_KEYBOARD")) == NULL)
+    s = mch_getenv("HANGUL_KEYBOARD_TYPE");
 
   if (s) {
     if (*s == '2')
diff --git a/src/main.c b/src/main.c
index 13b1179711..d6a09b504c 100644
--- a/src/main.c
+++ b/src/main.c
@@ -2114,7 +2114,8 @@ process_env (
   linenr_T save_sourcing_lnum;
   scid_T save_sid;
 
-  if ((initstr = mch_getenv(env)) != NULL && *initstr != NUL) {
+  initstr = (char_u *)mch_getenv((char *)env);
+  if (initstr != NULL && *initstr != NUL) {
     if (is_viminit)
       vimrc_found(NULL, NULL);
     save_sourcing_name = sourcing_name;
diff --git a/src/mbyte.c b/src/mbyte.c
index 2ebf3cd98f..44f0f9d643 100644
--- a/src/mbyte.c
+++ b/src/mbyte.c
@@ -89,6 +89,7 @@
 #include "screen.h"
 #include "spell.h"
 #include "ui.h"
+#include "os/os.h"
 
 # define WINBYTE BYTE
 
@@ -3483,9 +3484,9 @@ char_u * enc_locale()              {
 #  if defined(HAVE_LOCALE_H) || defined(X_LOCALE)
     if ((s = setlocale(LC_CTYPE, NULL)) == NULL || *s == NUL)
 #  endif
-      if ((s = getenv("LC_ALL")) == NULL || *s == NUL)
-        if ((s = getenv("LC_CTYPE")) == NULL || *s == NUL)
-          s = getenv("LANG");
+      if ((s = (char *)mch_getenv("LC_ALL")) == NULL || *s == NUL)
+        if ((s = (char *)mch_getenv("LC_CTYPE")) == NULL || *s == NUL)
+          s = (char *)mch_getenv("LANG");
 
   if (s == NULL || *s == NUL)
     return FAIL;
diff --git a/src/message.c b/src/message.c
index f6e8d3d9bd..6948cefe12 100644
--- a/src/message.c
+++ b/src/message.c
@@ -30,6 +30,7 @@
 #include "screen.h"
 #include "term.h"
 #include "ui.h"
+#include "os/os.h"
 
 #if defined(FEAT_FLOAT) && defined(HAVE_MATH_H)
 # include <math.h>
@@ -736,11 +737,11 @@ int delete_first_msg(void)         {
 void ex_messages(exarg_T *eap)
 {
   struct msg_hist *p;
-  char_u          *s;
+  const char      *s;
 
   msg_hist_off = TRUE;
 
-  s = mch_getenv((char_u *)"LANG");
+  s = mch_getenv("LANG");
   if (s != NULL && *s != NUL)
     msg_attr((char_u *)
         _("Messages maintainer: Bram Moolenaar <Bram@vim.org>"),
diff --git a/src/misc1.c b/src/misc1.c
index ab21f8d6a5..b391cb1ee4 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -45,11 +45,6 @@
 #include "undo.h"
 #include "window.h"
 #include "os/os.h"
-
-#ifdef HAVE_CRT_EXTERNS_H
-#include <crt_externs.h>
-#endif
-
 static char_u *vim_version_dir(char_u *vimdir);
 static char_u *remove_tail(char_u *p, char_u *pend, char_u *name);
 static void init_users(void);
@@ -2727,7 +2722,7 @@ void init_homedir(void)          {
   vim_free(homedir);
   homedir = NULL;
 
-  var = mch_getenv((char_u *)"HOME");
+  var = (char_u *)mch_getenv("HOME");
 
   if (var != NULL && *var == NUL)       /* empty is same as not set */
     var = NULL;
@@ -3052,7 +3047,7 @@ char_u *vim_getenv(char_u *name, int *mustfree)
   int vimruntime;
 
 
-  p = mch_getenv(name);
+  p = (char_u *)mch_getenv((char *)name);
   if (p != NULL && *p == NUL)       /* empty is the same as not set */
     p = NULL;
 
@@ -3073,7 +3068,7 @@ char_u *vim_getenv(char_u *name, int *mustfree)
       && *default_vimruntime_dir == NUL
 #endif
       ) {
-    p = mch_getenv((char_u *)"VIM");
+    p = (char_u *)mch_getenv("VIM");
     if (p != NULL && *p == NUL)             /* empty is the same as not set */
       p = NULL;
     if (p != NULL) {
@@ -3081,7 +3076,7 @@ char_u *vim_getenv(char_u *name, int *mustfree)
       if (p != NULL)
         *mustfree = TRUE;
       else
-        p = mch_getenv((char_u *)"VIM");
+        p = (char_u *)mch_getenv("VIM");
 
     }
   }
@@ -3223,21 +3218,7 @@ static char_u *remove_tail(char_u *p, char_u *pend, char_u *name)
  */
 void vim_setenv(char_u *name, char_u *val)
 {
-#ifdef HAVE_SETENV
   mch_setenv((char *)name, (char *)val, 1);
-#else
-  char_u      *envbuf;
-
-  /*
-   * Putenv does not copy the string, it has to remain
-   * valid.  The allocated memory will never be freed.
-   */
-  envbuf = alloc((unsigned)(STRLEN(name) + STRLEN(val) + 2));
-  if (envbuf != NULL) {
-    sprintf((char *)envbuf, "%s=%s", name, val);
-    putenv((char *)envbuf);
-  }
-#endif
   /*
    * When setting $VIMRUNTIME adjust the directory to find message
    * translations to $VIMRUNTIME/lang.
@@ -3258,35 +3239,17 @@ void vim_setenv(char_u *name, char_u *val)
  */
 char_u *get_env_name(expand_T *xp, int idx)
 {
-# if defined(AMIGA) || defined(__MRC__) || defined(__SC__)
-  /*
-   * No environ[] on the Amiga and on the Mac (using MPW).
-   */
-  return NULL;
-# else
-# if !defined(__WIN32__) && !defined(HAVE__NSGETENVIRON)
-  /* Borland C++ 5.2 has this in a header file. */
-  extern char         **environ;
-# else
-  char **environ = *_NSGetEnviron();
-# endif
 # define ENVNAMELEN 100
+  // this static buffer is needed to avoid a memory leak in ExpandGeneric
   static char_u name[ENVNAMELEN];
-  char_u              *str;
-  int n;
-
-  str = (char_u *)environ[idx];
-  if (str == NULL)
+  char *envname = mch_getenvname_at_index(idx);
+  if (envname) {
+    vim_strncpy(name, (char_u *)envname, ENVNAMELEN - 1);
+    vim_free(envname);
+    return name;
+  } else {
     return NULL;
-
-  for (n = 0; n < ENVNAMELEN - 1; ++n) {
-    if (str[n] == '=' || str[n] == NUL)
-      break;
-    name[n] = str[n];
   }
-  name[n] = NUL;
-  return name;
-# endif
 }
 
 /*
@@ -3396,7 +3359,7 @@ home_replace (
   if (homedir != NULL)
     dirlen = STRLEN(homedir);
 
-  homedir_env_orig = homedir_env = mch_getenv((char_u *)"HOME");
+  homedir_env_orig = homedir_env = (char_u *)mch_getenv("HOME");
   /* Empty is the same as not set. */
   if (homedir_env != NULL && *homedir_env == NUL)
     homedir_env = NULL;
diff --git a/src/misc2.c b/src/misc2.c
index 1b1693a72a..92a6af598b 100644
--- a/src/misc2.c
+++ b/src/misc2.c
@@ -2250,154 +2250,6 @@ int pathcmp(const char *p, const char *q, int maxlen)
 #endif
 
 /*
- * The putenv() implementation below comes from the "screen" program.
- * Included with permission from Juergen Weigert.
- * See pty.c for the copyright notice.
- */
-
-/*
- *  putenv  --	put value into environment
- *
- *  Usage:  i = putenv (string)
- *    int i;
- *    char  *string;
- *
- *  where string is of the form <name>=<value>.
- *  Putenv returns 0 normally, -1 on error (not enough core for malloc).
- *
- *  Putenv may need to add a new name into the environment, or to
- *  associate a value longer than the current value with a particular
- *  name.  So, to make life simpler, putenv() copies your entire
- *  environment into the heap (i.e. malloc()) from the stack
- *  (i.e. where it resides when your process is initiated) the first
- *  time you call it.
- *
- *  (history removed, not very interesting.  See the "screen" sources.)
- */
-
-#if !defined(HAVE_SETENV) && !defined(HAVE_PUTENV)
-
-#define EXTRASIZE 5             /* increment to add to env. size */
-
-static int envsize = -1;        /* current size of environment */
-extern
-char **environ;                 /* the global which is your env. */
-
-static int findenv(char *name);  /* look for a name in the env. */
-static int newenv(void);       /* copy env. from stack to heap */
-static int moreenv(void);      /* incr. size of env. */
-
-int putenv(const char *string)
-{
-  int i;
-  char    *p;
-
-  if (envsize < 0) {            /* first time putenv called */
-    if (newenv() < 0)           /* copy env. to heap */
-      return -1;
-  }
-
-  i = findenv((char *)string);   /* look for name in environment */
-
-  if (i < 0) {                  /* name must be added */
-    for (i = 0; environ[i]; i++) ;
-    if (i >= (envsize - 1)) {   /* need new slot */
-      if (moreenv() < 0)
-        return -1;
-    }
-    p = (char *)alloc((unsigned)(strlen(string) + 1));
-    if (p == NULL)              /* not enough core */
-      return -1;
-    environ[i + 1] = 0;         /* new end of env. */
-  } else   {                    /* name already in env. */
-    p = vim_realloc(environ[i], strlen(string) + 1);
-    if (p == NULL)
-      return -1;
-  }
-  sprintf(p, "%s", string);     /* copy into env. */
-  environ[i] = p;
-
-  return 0;
-}
-
-static int findenv(char *name)
-{
-  char    *namechar, *envchar;
-  int i, found;
-
-  found = 0;
-  for (i = 0; environ[i] && !found; i++) {
-    envchar = environ[i];
-    namechar = name;
-    while (*namechar && *namechar != '=' && (*namechar == *envchar)) {
-      namechar++;
-      envchar++;
-    }
-    found = ((*namechar == '\0' || *namechar == '=') && *envchar == '=');
-  }
-  return found ? i - 1 : -1;
-}
-
-static int newenv(void)                {
-  char    **env, *elem;
-  int i, esize;
-
-  for (i = 0; environ[i]; i++)
-    ;
-  esize = i + EXTRASIZE + 1;
-  env = (char **)alloc((unsigned)(esize * sizeof (elem)));
-  if (env == NULL)
-    return -1;
-
-  for (i = 0; environ[i]; i++) {
-    elem = (char *)alloc((unsigned)(strlen(environ[i]) + 1));
-    if (elem == NULL)
-      return -1;
-    env[i] = elem;
-    strcpy(elem, environ[i]);
-  }
-
-  env[i] = 0;
-  environ = env;
-  envsize = esize;
-  return 0;
-}
-
-static int moreenv(void)                {
-  int esize;
-  char    **env;
-
-  esize = envsize + EXTRASIZE;
-  env = (char **)vim_realloc((char *)environ, esize * sizeof (*env));
-  if (env == 0)
-    return -1;
-  environ = env;
-  envsize = esize;
-  return 0;
-}
-
-# ifdef USE_VIMPTY_GETENV
-char_u *vimpty_getenv(const char_u *string)
-{
-  int i;
-  char_u *p;
-
-  if (envsize < 0)
-    return NULL;
-
-  i = findenv((char *)string);
-
-  if (i < 0)
-    return NULL;
-
-  p = vim_strchr((char_u *)environ[i], '=');
-  return p + 1;
-}
-# endif
-
-#endif /* !defined(HAVE_SETENV) && !defined(HAVE_PUTENV) */
-
-/*
  * Return 0 for not writable, 1 for writable file, 2 for a dir which we have
  * rights to write into.
  */
diff --git a/src/option.c b/src/option.c
index 8daac5b5e1..e257186cf2 100644
--- a/src/option.c
+++ b/src/option.c
@@ -67,6 +67,7 @@
 #include "ui.h"
 #include "undo.h"
 #include "window.h"
+#include "os/os.h"
 
 /*
  * The options that are local to a window or buffer have "indir" set to one of
@@ -1961,7 +1962,7 @@ void set_init_1(void)          {
   p_cp = TRUE;
 
   /* Use POSIX compatibility when $VIM_POSIX is set. */
-  if (mch_getenv((char_u *)"VIM_POSIX") != NULL) {
+  if (mch_getenv("VIM_POSIX") != NULL) {
     set_string_default("cpo", (char_u *)CPO_ALL);
     set_string_default("shm", (char_u *)"A");
   }
@@ -1970,7 +1971,7 @@ void set_init_1(void)          {
    * Find default value for 'shell' option.
    * Don't use it if it is empty.
    */
-  if (((p = mch_getenv((char_u *)"SHELL")) != NULL && *p != NUL)
+  if (((p = (char_u *)mch_getenv("SHELL")) != NULL && *p != NUL)
       )
     set_string_default("sh", p);
 
@@ -2170,7 +2171,7 @@ void set_init_1(void)          {
    * NOTE: mlterm's author is being asked to 'set' a variable
    *       instead of an environment variable due to inheritance.
    */
-  if (mch_getenv((char_u *)"MLTERM") != NULL)
+  if (mch_getenv("MLTERM") != NULL)
     set_option_value((char_u *)"tbidi", 1L, NULL, 0);
 
   /* Parse default for 'fillchars'. */
@@ -2447,7 +2448,7 @@ static char_u *term_bg_default(void)                     {
       || STRCMP(T_NAME, "screen.linux") == 0
       || STRCMP(T_NAME, "cygwin") == 0
       || STRCMP(T_NAME, "putty") == 0
-      || ((p = mch_getenv((char_u *)"COLORFGBG")) != NULL
+      || ((p = (char_u *)mch_getenv("COLORFGBG")) != NULL
           && (p = vim_strrchr(p, ';')) != NULL
           && ((p[1] >= '0' && p[1] <= '6') || p[1] == '8')
           && p[2] == NUL))
diff --git a/src/os/env.c b/src/os/env.c
new file mode 100644
index 0000000000..9025b1c8ac
--- /dev/null
+++ b/src/os/env.c
@@ -0,0 +1,65 @@
+/* vi:set ts=2 sts=2 sw=2:
+ *
+ * VIM - Vi IMproved	by Bram Moolenaar
+ *
+ * Do ":help uganda"  in Vim to read copying and usage conditions.
+ * Do ":help credits" in Vim to see a list of people who contributed.
+ * See README.txt for an overview of the Vim source code.
+ */
+
+/*
+ * env.c -- environment variable access
+ */
+
+#include <uv.h>
+
+#include "os.h"
+#include "../misc2.h"
+
+#ifdef HAVE_CRT_EXTERNS_H
+#include <crt_externs.h>
+#endif
+
+const char *mch_getenv(const char *name)
+{
+  return getenv(name);
+}
+
+int mch_setenv(const char *name, const char *value, int overwrite)
+{
+  return setenv(name, value, overwrite);
+}
+
+char *mch_getenvname_at_index(size_t index)
+{
+# if defined(AMIGA) || defined(__MRC__) || defined(__SC__)
+  /*
+   * No environ[] on the Amiga and on the Mac (using MPW).
+   */
+  return NULL;
+# else
+# if defined(HAVE__NSGETENVIRON)
+  char **environ = *_NSGetEnviron();
+# elif !defined(__WIN32__)
+  /* Borland C++ 5.2 has this in a header file. */
+  extern char         **environ;
+# endif
+  // check if index is inside the environ array
+  for (size_t i = 0; i < index; i++) {
+    if (environ[i] == NULL) {
+      return NULL;
+    }
+  }
+  char *str = environ[index];
+  if (str == NULL) {
+    return NULL;
+  }
+  int namesize = 0;
+  while (str[namesize] != '=' && str[namesize] != NUL) {
+    namesize++;
+  }
+  char *name = (char *)vim_strnsave((char_u *)str, namesize);
+  return name;
+# endif
+}
+
diff --git a/src/os/os.h b/src/os/os.h
index bc7496ed58..266b253e86 100644
--- a/src/os/os.h
+++ b/src/os/os.h
@@ -9,5 +9,8 @@ int mch_dirname(char_u *buf, int len);
 int mch_get_absolute_path(char_u *fname, char_u *buf, int len, int force);
 int mch_is_absolute_path(char_u *fname);
 int mch_isdir(char_u *name);
+const char *mch_getenv(const char *name);
+int mch_setenv(const char *name, const char *value, int overwrite);
+char *mch_getenvname_at_index(size_t index);
 
 #endif
diff --git a/src/os_unix.c b/src/os_unix.c
index 40eba52da8..5a01f07c36 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -1349,7 +1349,7 @@ int mch_can_exe(char_u *name)
                                                       name[2] == '/'))))
     return executable_file(name);
 
-  p = (char_u *)getenv("PATH");
+  p = (char_u *)mch_getenv("PATH");
   if (p == NULL || *p == NUL)
     return -1;
   buf = alloc((unsigned)(STRLEN(name) + STRLEN(p) + 2));
@@ -1837,9 +1837,9 @@ int mch_get_shellsize()         {
    *    the ioctl() values!
    */
   if (columns == 0 || rows == 0 || vim_strchr(p_cpo, CPO_TSIZE) != NULL) {
-    if ((p = (char_u *)getenv("LINES")))
+    if ((p = (char_u *)mch_getenv("LINES")))
       rows = atoi((char *)p);
-    if ((p = (char_u *)getenv("COLUMNS")))
+    if ((p = (char_u *)mch_getenv("COLUMNS")))
       columns = atoi((char *)p);
   }
 
@@ -1950,12 +1950,7 @@ int options;                    /* SHELL_*, see vim.h */
   int fd_toshell[2];                    /* for pipes */
   int fd_fromshell[2];
   int pipe_error = FALSE;
-# ifdef HAVE_SETENV
   char envbuf[50];
-# else
-  static char envbuf_Rows[20];
-  static char envbuf_Columns[20];
-# endif
   int did_settmode = FALSE;             /* settmode(TMODE_RAW) called */
 
   newcmd = vim_strsave(p_sh);
@@ -2125,27 +2120,13 @@ int options;                    /* SHELL_*, see vim.h */
         }
 # endif
         /* Simulate to have a dumb terminal (for now) */
-# ifdef HAVE_SETENV
-        setenv("TERM", "dumb", 1);
+        mch_setenv("TERM", "dumb", 1);
         sprintf((char *)envbuf, "%ld", Rows);
-        setenv("ROWS", (char *)envbuf, 1);
+        mch_setenv("ROWS", (char *)envbuf, 1);
         sprintf((char *)envbuf, "%ld", Rows);
-        setenv("LINES", (char *)envbuf, 1);
+        mch_setenv("LINES", (char *)envbuf, 1);
         sprintf((char *)envbuf, "%ld", Columns);
-        setenv("COLUMNS", (char *)envbuf, 1);
-# else
-        /*
-         * Putenv does not copy the string, it has to remain valid.
-         * Use a static array to avoid losing allocated memory.
-         */
-        putenv("TERM=dumb");
-        sprintf(envbuf_Rows, "ROWS=%ld", Rows);
-        putenv(envbuf_Rows);
-        sprintf(envbuf_Rows, "LINES=%ld", Rows);
-        putenv(envbuf_Rows);
-        sprintf(envbuf_Columns, "COLUMNS=%ld", Columns);
-        putenv(envbuf_Columns);
-# endif
+        mch_setenv("COLUMNS", (char *)envbuf, 1);
 
         /*
          * stderr is only redirected when using the GUI, so that a
diff --git a/src/os_unix_defs.h b/src/os_unix_defs.h
index 3aacac69a0..74b98ef68a 100644
--- a/src/os_unix_defs.h
+++ b/src/os_unix_defs.h
@@ -280,14 +280,6 @@
 # else
 int mch_rename(const char *src, const char *dest);
 # endif
-#  ifdef __MVS__
-/* on OS390 Unix getenv() doesn't return a pointer to persistent
- * storage -> use __getenv() */
-#   define mch_getenv(x) (char_u *)__getenv((char *)(x))
-#  else
-#   define mch_getenv(x) (char_u *)getenv((char *)(x))
-#  endif
-#  define mch_setenv(name, val, x) setenv(name, val, x)
 
 #if !defined(S_ISDIR) && defined(S_IFDIR)
 # define        S_ISDIR(m) (((m) & S_IFMT) == S_IFDIR)
diff --git a/src/term.c b/src/term.c
index 15a4320db4..4e405f732a 100644
--- a/src/term.c
+++ b/src/term.c
@@ -45,6 +45,7 @@
 #include "syntax.h"
 #include "ui.h"
 #include "window.h"
+#include "os/os.h"
 
 #ifdef HAVE_TGETENT
 # ifdef HAVE_TERMIOS_H
@@ -2021,7 +2022,7 @@ void termcapinit(char_u *name)
   term = name;
 
   if (term == NULL)
-    term = mch_getenv((char_u *)"TERM");
+    term = (char_u *)mch_getenv("TERM");
   if (term == NULL || *term == NUL)
     term = DEFAULT_TERM;
   set_string_option_direct((char_u *)"term", -1, term, OPT_FREE, 0);
diff --git a/test/unit/os/env.moon b/test/unit/os/env.moon
new file mode 100644
index 0000000000..b83fcac5f1
--- /dev/null
+++ b/test/unit/os/env.moon
@@ -0,0 +1,95 @@
+{:cimport, :internalize, :eq, :ffi, :lib, :cstr} = require 'test.unit.helpers'
+require 'lfs'
+
+-- fs = cimport './src/os/os.h'
+-- remove these statements once 'cimport' is working properly for misc1.h
+env = lib
+ffi.cdef [[
+const char *mch_getenv(const char *name);
+int mch_setenv(const char *name, const char *value, int override);
+char *mch_getenvname_at_index(size_t index);
+]]
+
+str_to_charp = (str) ->
+  cstr (string.len str), str
+
+NULL = ffi.cast 'void*', 0
+
+describe 'env function', ->
+
+  mch_setenv = (name, value, override) ->
+    env.mch_setenv (str_to_charp name), (str_to_charp value), override
+
+  mch_getenv = (name) ->
+    rval = env.mch_getenv (str_to_charp name)
+    if rval != NULL
+      ffi.string rval
+    else
+      NULL
+
+  describe 'mch_setenv', ->
+
+    OK = 0
+
+    it 'sets an env variable and returns OK', ->
+      name = 'NEOVIM_UNIT_TEST_SETENV_1N'
+      value = 'NEOVIM_UNIT_TEST_SETENV_1V'
+      eq nil, os.getenv name
+      eq OK, (mch_setenv name, value, 1)
+      eq value, os.getenv name
+
+    it "dosn't overwrite an env variable if overwrite is 0", ->
+      name = 'NEOVIM_UNIT_TEST_SETENV_2N'
+      value = 'NEOVIM_UNIT_TEST_SETENV_2V'
+      value_updated = 'NEOVIM_UNIT_TEST_SETENV_2V_UPDATED'
+      eq OK, (mch_setenv name, value, 0)
+      eq value, os.getenv name
+      eq OK, (mch_setenv name, value_updated, 0)
+      eq value, os.getenv name
+
+  describe 'mch_getenv', ->
+
+    it 'reads an env variable', ->
+      name = 'NEOVIM_UNIT_TEST_GETENV_1N'
+      value =  'NEOVIM_UNIT_TEST_GETENV_1V'
+      eq NULL, mch_getenv name
+      -- need to use mch_setenv, because lua dosn't have a setenv function
+      mch_setenv name, value, 1
+      eq value, mch_getenv name
+
+    it 'returns NULL if the env variable is not found', ->
+      name = 'NEOVIM_UNIT_TEST_GETENV_NOTFOUND'
+      eq NULL, mch_getenv name
+
+  describe 'mch_getenvname_at_index', ->
+
+    it 'returns names of environment variables', ->
+      test_name = 'NEOVIM_UNIT_TEST_GETENVNAME_AT_INDEX_1N'
+      test_value =  'NEOVIM_UNIT_TEST_GETENVNAME_AT_INDEX_1V'
+      mch_setenv test_name, test_value, 1
+      i = 0
+      names = {}
+      found_name = false
+      name = env.mch_getenvname_at_index i
+      while name != NULL
+        table.insert names, ffi.string name
+        if (ffi.string name) == test_name
+          found_name = true
+        i += 1
+        name = env.mch_getenvname_at_index i
+
+      eq true, (table.getn names) > 0
+      eq true, found_name
+
+    it 'returns NULL if the index is out of bounds', ->
+      huge = ffi.new 'size_t', 10000
+      maxuint32 = ffi.new 'size_t', 4294967295
+      eq NULL, env.mch_getenvname_at_index huge
+      eq NULL, env.mch_getenvname_at_index maxuint32
+      if ffi.abi '64bit'
+        -- couldn't use a bigger number because it gets converted to 
+        -- double somewere, should be big enough anyway
+        -- maxuint64 = ffi.new 'size_t', 18446744073709551615
+        maxuint64 = ffi.new 'size_t', 18446744073709000000
+        eq NULL, env.mch_getenvname_at_index maxuint64
+