[Kindle NT] fix terminal and timesync (#12765)

Closes #12760
Credits go to @benoit-pierre (Thank you!)

frontend/util.lua

@@ -1635,4 +1635,14 @@ function util.round_decimal(num, points)
     return math.floor(num * op) / op
 end
 
+function util.which(command, path)
+    path = path or os.getenv("PATH") or ""
+    for p in path:gmatch("([^:]+)") do
+        p = p .. "/" .. command
+        if ffiUtil.isExecutable(p) then
+            return p
+        end
+    end
+end
+
 return util

plugins/terminal.koplugin/main.lua

@@ -6,6 +6,7 @@ This plugin provides a terminal emulator (VT52 (+some ANSI and some VT100))
 
 local Device = require("device")
 local logger = require("logger")
+local util = require("util")
 local ffi = require("ffi")
 local C = ffi.C
 require("ffi/posix_h")
@@ -76,10 +77,11 @@ local WidgetContainer = require("ui/widget/container/widgetcontainer")
 local TermInputText = require("terminputtext")
 local TextWidget = require("ui/widget/textwidget")
 local bit = require("bit")
+local ffiUtil = require("ffi/util")
 local lfs = require("libs/libkoreader-lfs")
 local _ = require("gettext")
 local C_ = _.pgettext
-local T = require("ffi/util").template
+local T = ffiUtil.template
 
 local CHUNK_SIZE = 80 * 40 -- max. nb of read bytes (reduce this, if taps are not detected)
 
@@ -94,7 +96,7 @@ local Terminal = WidgetContainer:extend{
 
 function Terminal:isExecutable(file)
     -- check if file is an executable or a command in PATH
-    return os.execute(string.format("test -x %s || command -v %s", file, file)) == 0
+    return ffiUtil.isExecutable(file) or util.which(file) ~= nil
 end
 
 -- Try SHELL environment variable and some standard shells

plugins/timesync.koplugin/main.lua

@@ -1,9 +1,10 @@
 local Device = require("device")
-local lfs = require("libs/libkoreader-lfs")
-
 local ffi = require("ffi")
 local C = ffi.C
+local lfs = require("libs/libkoreader-lfs")
+local util = require("util")
 require("ffi/posix_h")
+
 -- We need to be root to be able to set the time (CAP_SYS_TIME)
 if C.getuid() ~= 0 then
     return { disabled = true, }
@@ -11,19 +12,16 @@ end
 
 local ntp_cmd
 -- Check if we have access to ntpd or ntpdate
-if os.execute("command -v ntpd >/dev/null") == 0 then
+local ntpd = util.which("ntpd")
+if ntpd then
     -- Make sure it's actually busybox's implementation, as the syntax may otherwise differ...
     -- (Of particular note, Kobo ships busybox ntpd, but not ntpdate; and Kindle ships ntpdate and !busybox ntpd).
-    local path = os.getenv("PATH") or ""
-    for p in path:gmatch("([^:]+)") do
-        local sym = lfs.symlinkattributes(p .. "/ntpd")
-        if sym and sym.mode == "link" and string.sub(sym.target, -7) == "busybox" then
-            ntp_cmd = "ntpd -q -n -p pool.ntp.org"
-            break
-        end
+    local sym = lfs.symlinkattributes(ntpd)
+    if sym and sym.mode == "link" and string.sub(sym.target, -7) == "busybox" then
+        ntp_cmd = "ntpd -q -n -p pool.ntp.org"
     end
 end
-if not ntp_cmd and os.execute("command -v ntpdate >/dev/null") == 0 then
+if not ntp_cmd and util.which("ntpdate") then
     ntp_cmd = "ntpdate pool.ntp.org"
 end
 if not ntp_cmd then