add option to redirect log output to file

3 files changed, 100 insertions, 11 deletions

diff --git a/luaotfload-override.lua b/luaotfload-override.lua
index 225ac68..39cc172 100644
--- a/luaotfload-override.lua
+++ b/luaotfload-override.lua
@@ -15,17 +15,23 @@ because we lack a user interface to toggle per-subsystem tracing.
 
 local module_name       = "luaotfload"
 
+local ioopen            = io.open
+local iowrite           = io.write
+local lfsisdir          = lfs.isdir
+local lfsisfile         = lfs.isfile
+local md5sumhexa        = md5.sumhexa
+local osdate            = os.date
+local ostime            = os.time
 local select            = select
 local stringformat      = string.format
+local stringsub         = string.sub
 local tableconcat       = table.concat
+local texio_write_nl    = texio.write_nl
 local texiowrite_nl     = texio.write_nl
+local texio_write       = texio.write
 local texiowrite        = texio.write
 local type              = type
 
-local texio_write_nl    = texio.write_nl
-local texio_write       = texio.write
-local iowrite           = io.write
-
 --[[doc--
 We recreate the verbosity levels previously implemented in font-nms:
 
@@ -62,9 +68,67 @@ logs.getloglevel    = get_loglevel
 logs.get_loglevel   = get_loglevel
 logs.get_log_level  = get_loglevel
 
-local set_logout = function (s)
+local writeln --- scope so we can change it
+
+local log_msg = [[
+logging output redirected to %s
+to monitor the progress run "tail -f %s" in another terminal
+]]
+
+local tmppath = os.getenv "TMPDIR" or "/tmp"
+
+local choose_logfile = function ( )
+    if lfsisdir (tmppath) then
+        local fname
+        repeat --- ensure that file of that name doesn’t exist
+            fname = tmppath .. "/luaotfload-log-"
+                            .. stringsub (md5sumhexa (ostime ()), 1, 8)
+        until not lfsisfile (fname)
+        iowrite (stringformat (log_msg, fname, fname))
+        return ioopen (fname, "w")
+    end
+    --- missing /tmp
+    return false
+end
+
+local set_logout = function (s, finalizers)
     if s == "stdout" then
         logout = "term"
+    elseif s == "file" then --- inject custom logger
+        local chan = choose_logfile ()
+        chan:write (stringformat ("logging initiated at %s",
+                                  osdate ("%F %T", ostime ())))
+        local writefile = function (...)
+            if select ("#", ...) == 2 then
+                chan:write (select (2, ...))
+            else
+                chan:write (select (1, ...))
+            end
+        end
+        local writefile_nl= function (...)
+            chan:write "\n"
+            if select ("#", ...) == 2 then
+                chan:write (select (2, ...))
+            else
+                chan:write (select (1, ...))
+            end
+        end
+
+        local writeln_orig = writeln
+
+        texiowrite    = writefile
+        texiowrite_nl = writefile_nl
+        writeln       = writefile_nl
+
+        finalizers[#finalizers+1] = function ()
+            chan:write (stringformat ("\nlogging finished at %s\n",
+                                      osdate ("%F %T", ostime ())))
+            chan:close ()
+            texiowrite    = texio.write
+            texiowrite_nl = texio.write_nl
+            writeln       = writeln_orig
+        end
+        return finalizers
     --else --- remains “log”
     end
 end
@@ -92,7 +156,6 @@ end
 io.stdout:setvbuf "no"
 io.stderr:setvbuf "no"
 
-local writeln
 if tex and (tex.jobname or tex.formatname) then
     --- TeX
     writeln = texiowrite_nl
@@ -155,7 +218,7 @@ local names_report = function (mode, lvl, ...)
     if loglevel >= lvl then
         if mode == "log" then
             log (...)
-        elseif mode == "both" then
+        elseif mode == "both" and log ~= "stdout" then
             log (...)
             stdout (...)
         else
diff --git a/luaotfload-tool.lua b/luaotfload-tool.lua
index 45a75ba..392be6e 100755
--- a/luaotfload-tool.lua
+++ b/luaotfload-tool.lua
@@ -902,6 +902,22 @@ actions.list = function (job)
     return true, true
 end
 
+--- stuff to be carried out prior to exit
+
+local finalizers = { }
+
+--- returns false if at least one of the actions failed, mainly
+--- for closing io channels
+local finalize = function ()
+    local success = true
+    for _, fun in next, finalizers do
+        if type (fun) == "function" then
+            if fun () == false then success = false end
+        end
+    end
+    return success
+end
+
 --[[--
 Command-line processing.
 mkluatexfontdb.lua relies on the script alt_getopt to process argv and
@@ -985,7 +1001,7 @@ local process_cmdline = function ( ) -- unit -> jobspec
         elseif v == "log" then
             local str = optarg[n]
             if str then
-                logs.set_logout(str)
+                finalizers = logs.set_logout(str, finalizers)
             end
         elseif v == "find" then
             action_pending["query"] = true
@@ -1065,7 +1081,11 @@ local main = function ( ) -- unit -> int
         if exit then break end
     end
 
-    texiowrite_nl""
+    if finalize () == false then
+        retval = -1
+    end
+
+    --texiowrite_nl""
     return retval
 end
 
diff --git a/luaotfload-tool.rst b/luaotfload-tool.rst
index 7b75367..31a1010 100644
--- a/luaotfload-tool.rst
+++ b/luaotfload-tool.rst
@@ -116,8 +116,14 @@ miscellaneous
 --verbose=N, -v         Set verbosity level to *n* or the number of
                         repetitions of ``-v``.
 --quiet                 No verbose output (log level set to zero).
---log=stdout            Redirect log output to terminal (for database
-                        troubleshooting).
+--log=CHANNEL           Redirect log output (for database
+                        troubleshooting), where *CHANNEL* can be
+
+                        1) ``stdout`` -> all output will be
+                           dumped to the terminal; or
+                        2) ``file`` -> write to a file to the temporary
+                           directory (the name will be chosen
+                           automatically (**experimental!**).
 
 --version, -V           Show version number and exit.
 --help, -h              Show help message and exit.