diff --git a/src/diff.c b/src/diff.c
index af40b1295a..67d941c35a 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -25,6 +25,7 @@
 #include "undo.h"
 #include "window.h"
 #include "os/os.h"
+#include "os/shell.h"
 
 static int diff_busy = FALSE;    // ex_diffgetput() is busy
 
@@ -840,7 +841,11 @@ static void diff_file(char_u *tmp_orig, char_u *tmp_new, char_u *tmp_diff)
                    tmp_orig, tmp_new);
       append_redir(cmd, (int)len, p_srr, tmp_diff);
       block_autocmds(); /* Avoid ShellCmdPost stuff */
-      (void)call_shell(cmd, SHELL_FILTER | SHELL_SILENT | SHELL_DOOUT, NULL);
+      (void)call_shell(
+          cmd,
+          kShellOptFilter | kShellOptSilent | kShellOptDoOut,
+          NULL
+          );
       unblock_autocmds();
       vim_free(cmd);
     }
@@ -943,7 +948,7 @@ void ex_diffpatch(exarg_T *eap)
 #endif  // ifdef UNIX
     // Avoid ShellCmdPost stuff
     block_autocmds();
-    (void)call_shell(buf, SHELL_FILTER | SHELL_COOKED, NULL);
+    (void)call_shell(buf, kShellOptFilter | kShellOptCooked, NULL);
     unblock_autocmds();
   }
 
diff --git a/src/eval.c b/src/eval.c
index 847082aebf..f3644cceb0 100644
--- a/src/eval.c
+++ b/src/eval.c
@@ -61,6 +61,7 @@
 #include "version.h"
 #include "window.h"
 #include "os/os.h"
+#include "os/shell.h"
 
 #if defined(FEAT_FLOAT) && defined(HAVE_MATH_H)
 # include <math.h>
@@ -14543,7 +14544,7 @@ static void f_system(typval_T *argvars, typval_T *rettv)
   }
 
   res = get_cmd_output(get_tv_string(&argvars[0]), infile,
-      SHELL_SILENT | SHELL_COOKED);
+      kShellOptSilent | kShellOptCooked);
 
 #ifdef USE_CR
   /* translate <CR> into <NL> */
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 335425b919..85b91741aa 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -57,6 +57,7 @@
 #include "undo.h"
 #include "window.h"
 #include "os/os.h"
+#include "os/shell.h"
 
 static int linelen(int *has_tab);
 static void do_filter(linenr_T line1, linenr_T line2, exarg_T *eap,
@@ -1023,21 +1024,21 @@ do_filter (
    */
 
   if (do_out)
-    shell_flags |= SHELL_DOOUT;
+    shell_flags |= kShellOptDoOut;
 
   if (!do_in && do_out && !p_stmp) {
     // Use a pipe to fetch stdout of the command, do not use a temp file.
-    shell_flags |= SHELL_READ;
+    shell_flags |= kShellOptRead;
     curwin->w_cursor.lnum = line2;
   } else if (do_in && !do_out && !p_stmp) {
     // Use a pipe to write stdin of the command, do not use a temp file.
-    shell_flags |= SHELL_WRITE;
+    shell_flags |= kShellOptWrite;
     curbuf->b_op_start.lnum = line1;
     curbuf->b_op_end.lnum = line2;
   } else if (do_in && do_out && !p_stmp) {
     // Use a pipe to write stdin and fetch stdout of the command, do not
     // use a temp file.
-    shell_flags |= SHELL_READ|SHELL_WRITE;
+    shell_flags |= kShellOptRead | kShellOptWrite;
     curbuf->b_op_start.lnum = line1;
     curbuf->b_op_end.lnum = line2;
     curwin->w_cursor.lnum = line2;
@@ -1100,9 +1101,13 @@ do_filter (
    * 'u' to fix the text
    * Switch to cooked mode when not redirecting stdin, avoids that something
    * like ":r !cat" hangs.
-   * Pass on the SHELL_DOOUT flag when the output is being redirected.
+   * Pass on the kShellDoOut flag when the output is being redirected.
    */
-  if (call_shell(cmd_buf, SHELL_FILTER | SHELL_COOKED | shell_flags, NULL)) {
+  if (call_shell(
+        cmd_buf,
+        kShellOptFilter | kShellOptCooked | shell_flags,
+        NULL
+        )) {
     redraw_later_clear();
     wait_return(FALSE);
   }
@@ -1133,7 +1138,7 @@ do_filter (
 
     read_linecount = curbuf->b_ml.ml_line_count - read_linecount;
 
-    if (shell_flags & SHELL_READ) {
+    if (shell_flags & kShellOptRead) {
       curbuf->b_op_start.lnum = line2 + 1;
       curbuf->b_op_end.lnum = curwin->w_cursor.lnum;
       appended_lines_mark(line2, read_linecount);
@@ -1256,7 +1261,7 @@ do_shell (
   if (!swapping_screen())
     windgoto(msg_row, msg_col);
   cursor_on();
-  (void)call_shell(cmd, SHELL_COOKED | flags, NULL);
+  (void)call_shell(cmd, kShellOptCooked | flags, NULL);
   did_check_timestamps = FALSE;
   need_check_timestamps = TRUE;
 
diff --git a/src/ex_cmds2.c b/src/ex_cmds2.c
index ffa91626f3..8ea817f6ec 100644
--- a/src/ex_cmds2.c
+++ b/src/ex_cmds2.c
@@ -43,6 +43,7 @@
 #include "undo.h"
 #include "window.h"
 #include "os/os.h"
+#include "os/shell.h"
 
 static void cmd_source(char_u *fname, exarg_T *eap);
 
@@ -3518,7 +3519,7 @@ static char_u **find_locales(void)
   /* Find all available locales by running command "locale -a".  If this
    * doesn't work we won't have completion. */
   char_u *locale_a = get_cmd_output((char_u *)"locale -a",
-      NULL, SHELL_SILENT);
+      NULL, kShellOptSilent);
   if (locale_a == NULL)
     return NULL;
   ga_init2(&locales_ga, sizeof(char_u *), 20);
diff --git a/src/misc1.c b/src/misc1.c
index 8b96bb2235..1fbc14885d 100644
--- a/src/misc1.c
+++ b/src/misc1.c
@@ -49,6 +49,7 @@
 #include "undo.h"
 #include "window.h"
 #include "os/os.h"
+#include "os/shell.h"
 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);
@@ -3670,7 +3671,7 @@ get_cmd_output (
    * Don't check timestamps here.
    */
   ++no_check_timestamps;
-  call_shell(command, SHELL_DOOUT | SHELL_EXPAND | flags, NULL);
+  call_shell(command, kShellOptDoOut | kShellOptExpand | flags, NULL);
   --no_check_timestamps;
 
   vim_free(command);
diff --git a/src/os/shell.h b/src/os/shell.h
index c9dbc4ce9e..8cee4b8a90 100644
--- a/src/os/shell.h
+++ b/src/os/shell.h
@@ -5,6 +5,17 @@
 
 #include "types.h"
 
+// Flags for mch_call_shell() second argument
+typedef enum {
+  kShellOptFilter = 1,  // filtering text
+  kShellOptExpand = 2,  // expanding wildcards
+  kShellOptCooked = 4,  // set term to cooked mode
+  kShellOptDoOut = 8,   // redirecting output
+  kShellOptSilent = 16, // don't print error returned by command
+  kShellOptRead = 32,   // read lines and insert into buffer
+  kShellOptWrite = 64   // write lines from buffer
+} ShellOpts;
+
 char ** shell_build_argv(char_u *cmd, char_u *extra_shell_arg);
 void shell_free_argv(char **argv);
 
diff --git a/src/os_unix.c b/src/os_unix.c
index 3efa1a26c2..0a6a8a2794 100644
--- a/src/os_unix.c
+++ b/src/os_unix.c
@@ -1681,7 +1681,7 @@ waitstatus  *status;
   return wait_pid;
 }
 
-int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
+int mch_call_shell(char_u *cmd, ShellOpts opts, char_u *extra_shell_arg)
 {
   int tmode = cur_tmode;
 
@@ -1708,7 +1708,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
   int did_settmode = FALSE;             /* settmode(TMODE_RAW) called */
 
   out_flush();
-  if (options & SHELL_COOKED)
+  if (opts & kShellOptCooked)
     settmode(TMODE_COOK);               /* set to normal mode */
 
   argv = shell_build_argv(cmd, extra_shell_arg);
@@ -1722,8 +1722,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
    * input from the buffer: Try using a pseudo-tty to get the stdin/stdout
    * of the executed command into the Vim window.  Or use a pipe.
    */
-  if ((options & (SHELL_READ|SHELL_WRITE))
-      ) {
+  if (opts & (kShellOptRead|kShellOptWrite)) {
     {
       pipe_error = (pipe(fd_toshell) < 0);
       if (!pipe_error) {                            /* pipe create OK */
@@ -1744,8 +1743,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
 
     if ((pid = fork()) == -1) {         /* maybe we should use vfork() */
       MSG_PUTS(_("\nCannot fork\n"));
-      if ((options & (SHELL_READ|SHELL_WRITE))
-          ) {
+      if (opts & (kShellOptRead | kShellOptWrite)) {
         {
           close(fd_toshell[0]);
           close(fd_toshell[1]);
@@ -1756,7 +1754,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
     } else if (pid == 0) {    /* child */
       reset_signals();                  /* handle signals normally */
 
-      if (!show_shell_mess || (options & SHELL_EXPAND)) {
+      if (!show_shell_mess || (opts & kShellOptExpand)) {
         int fd;
 
         /*
@@ -1789,8 +1787,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
           /* Don't need this now that we've duplicated it */
           close(fd);
         }
-      } else if ((options & (SHELL_READ|SHELL_WRITE))
-                 ) {
+      } else if (opts & (kShellOptRead|kShellOptWrite)) {
 
 # ifdef HAVE_SETSID
         /* Create our own process group, so that the child and all its
@@ -1860,8 +1857,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
        * This is also used to pipe stdin/stdout to/from the external
        * command.
        */
-      if ((options & (SHELL_READ|SHELL_WRITE))
-          ) {
+      if (opts & (kShellOptRead|kShellOptWrite)) {
 # define BUFLEN 100             /* length for buffer, pseudo tty limit is 128 */
         char_u buffer[BUFLEN + 1];
         int buffer_off = 0;                     /* valid bytes in buffer[] */
@@ -1907,7 +1903,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
         old_State = State;
         State = EXTERNCMD;              /* don't redraw at window resize */
 
-        if ((options & SHELL_WRITE) && toshell_fd >= 0) {
+        if ((opts & kShellOptWrite) && toshell_fd >= 0) {
           /* Fork a process that will write the lines to the
            * external program. */
           if ((wpid = fork()) == -1) {
@@ -1963,7 +1959,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
           }
         }
 
-        if (options & SHELL_READ)
+        if (opts & kShellOptRead)
           ga_init2(&ga, 1, BUFLEN);
 
         noread_cnt = 0;
@@ -1986,10 +1982,10 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
            * typeahead.
            */
           len = 0;
-          if (!(options & SHELL_EXPAND)
-              && ((options &
-                   (SHELL_READ|SHELL_WRITE|SHELL_COOKED))
-                  != (SHELL_READ|SHELL_WRITE|SHELL_COOKED)
+          if (!(opts & kShellOptExpand)
+              && ((opts &
+                   (kShellOptRead|kShellOptWrite|kShellOptCooked))
+                  != (kShellOptRead|kShellOptWrite|kShellOptCooked)
                   )
               && wait_pid == 0
               && (ta_len > 0 || noread_cnt > 4)) {
@@ -2081,7 +2077,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
                * When writing buffer lines, drop the typed
                * characters (only check for CTRL-C).
                */
-              if (options & SHELL_WRITE)
+              if (opts & kShellOptWrite)
                 ta_len = 0;
               else if (toshell_fd >= 0) {
                 len = write(toshell_fd, (char *)ta_buf, (size_t)1);
@@ -2124,7 +2120,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
               goto finished;
 
             noread_cnt = 0;
-            if (options & SHELL_READ) {
+            if (opts & kShellOptRead) {
               /* Do NUL -> NL translation, append NL separated
                * lines to the current buffer. */
               for (i = 0; i < len; ++i) {
@@ -2227,7 +2223,7 @@ int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg)
         }
 finished:
         p_more = p_more_save;
-        if (options & SHELL_READ) {
+        if (opts & kShellOptRead) {
           if (ga.ga_len > 0) {
             append_ga_line(&ga);
             /* remember that the NL was missing */
@@ -2283,7 +2279,7 @@ finished:
             MSG_PUTS(_("\nCannot execute shell "));
             msg_outtrans(p_sh);
             msg_putchar('\n');
-          } else if (!(options & SHELL_SILENT)) {
+          } else if (!(opts & kShellOptSilent)) {
             MSG_PUTS(_("\nshell returned "));
             msg_outnum((long)retval);
             msg_putchar('\n');
@@ -2663,7 +2659,11 @@ int flags;                      /* EW_* flags */
   /*
    * execute the shell command
    */
-  i = call_shell(command, SHELL_EXPAND | SHELL_SILENT, extra_shell_arg);
+  i = call_shell(
+      command,
+      kShellOptExpand | kShellOptSilent,
+      extra_shell_arg
+      );
 
   /* When running in the background, give it some time to create the temp
    * file, but don't wait for it to finish. */
diff --git a/src/os_unix.h b/src/os_unix.h
index 48ce4f8e87..6b35d6822b 100644
--- a/src/os_unix.h
+++ b/src/os_unix.h
@@ -1,5 +1,8 @@
 #ifndef NEOVIM_OS_UNIX_H
 #define NEOVIM_OS_UNIX_H
+
+#include "os/shell.h"
+
 /* os_unix.c */
 void mch_write(char_u *s, int len);
 void mch_startjmp(void);
@@ -42,7 +45,7 @@ int mch_screenmode(char_u *arg);
 int mch_get_shellsize(void);
 void mch_set_shellsize(void);
 void mch_new_shellsize(void);
-int mch_call_shell(char_u *cmd, int options, char_u *extra_shell_arg);
+int mch_call_shell(char_u *cmd, ShellOpts opts, char_u *extra_shell_arg);
 int mch_expandpath(garray_T *gap, char_u *path, int flags);
 int mch_expand_wildcards(int num_pat, char_u **pat, int *num_file,
                          char_u ***file,
diff --git a/src/path.c b/src/path.c
index f643c8ec82..eceb5ca64d 100644
--- a/src/path.c
+++ b/src/path.c
@@ -9,6 +9,7 @@
 #include "misc1.h"
 #include "misc2.h"
 #include "os/os.h"
+#include "os/shell.h"
 #include "os_unix.h"
 #include "regexp.h"
 #include "tag.h"
@@ -1212,7 +1213,7 @@ expand_backtick (
     buffer = eval_to_string(cmd + 1, &p, TRUE);
   else
     buffer = get_cmd_output(cmd, NULL,
-        (flags & EW_SILENT) ? SHELL_SILENT : 0);
+        (flags & EW_SILENT) ? kShellOptSilent : 0);
   vim_free(cmd);
   if (buffer == NULL)
     return 0;
diff --git a/src/quickfix.c b/src/quickfix.c
index 90a60ce485..a0ec091ec7 100644
--- a/src/quickfix.c
+++ b/src/quickfix.c
@@ -2546,7 +2546,7 @@ void ex_make(exarg_T *eap)
   msg_outtrans(cmd);            /* show what we are doing */
 
   /* let the shell know if we are redirecting output or not */
-  do_shell(cmd, *p_sp != NUL ? SHELL_DOOUT : 0);
+  do_shell(cmd, *p_sp != NUL ? kShellOptDoOut : 0);
 
 
   res = qf_init(wp, fname, (eap->cmdidx != CMD_make
diff --git a/src/vim.h b/src/vim.h
index d45a61388b..cb33a3e17f 100644
--- a/src/vim.h
+++ b/src/vim.h
@@ -489,15 +489,6 @@ enum {
 #define REMAP_SCRIPT    -2      /* remap script-local mappings only */
 #define REMAP_SKIP      -3      /* no remapping for first char */
 
-/* Values for mch_call_shell() second argument */
-#define SHELL_FILTER    1       /* filtering text */
-#define SHELL_EXPAND    2       /* expanding wildcards */
-#define SHELL_COOKED    4       /* set term to cooked mode */
-#define SHELL_DOOUT     8       /* redirecting output */
-#define SHELL_SILENT    16      /* don't print error returned by command */
-#define SHELL_READ      32      /* read lines and insert into buffer */
-#define SHELL_WRITE     64      /* write lines from buffer */
-
 /* Values returned by mch_nodetype() */
 #define NODE_NORMAL     0       /* file or directory, check with os_isdir()*/
 #define NODE_WRITABLE   1       /* something we can write to (character