1 Correct answer
Are you executing ssh / sftp or something that involves Perl? Google shows a fair number of people asking about the error code being returned by Perl, on Unix-like systems and Windows. And this article suggests that ssh / sftp on Mac can return that code: 520927 .
As for generic debugging tools for LrTasks.execute(), I've probably spent more time over the years debugging invocations of external programs and shell scripts than any other single aspect of the SDK. The SDK environment is fragile,
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Are you executing ssh / sftp or something that involves Perl? Google shows a fair number of people asking about the error code being returned by Perl, on Unix-like systems and Windows. And this article suggests that ssh / sftp on Mac can return that code: 520927 .
As for generic debugging tools for LrTasks.execute(), I've probably spent more time over the years debugging invocations of external programs and shell scripts than any other single aspect of the SDK. The SDK environment is fragile, and of course, so many aspects of external programs are fragile (complicated syntax rules, buggy, undocumented, unpredictable, etc.), including the Mac and Windows shells used by execute() to execute the command lines.
Some issues to be aware of:
- The current directory execute() uses on Mac is "/", so be sure to test your command lines executing from there.
- Be sure to capture both standard output and standard error by using shell redirection. There may be clues there. I've included my Util.safeExecute() function below that does that.
- Beware of paths containing spaces, especially user names with spaces (yes, that can happen rarely on Mac). Quote command line arguments early and often to try to stay out of quoting hell.
- Once or twice, I've encountered issues on Mac with paths containing multibyte UTF-8 characters (it's more of a nightmare on Windows). I can't remember the details offhand. So see if any of the paths involved contain multibyte UTF-8 characters on one machine but not the other.
- You can get stack traces from LR of every call to error(), which infrequently can be useful to gather clues: Lightroom -traceback debugging tip
--[[----------------------------------------------------------------------------
public int exitCode, string output, string errOutput
safeExecute (string commandLine [, boolean getOutput])
Executes the command line "commandLine" in the platform shell via
LrTasks.execute, working around a bug in execute() on Windows where quoted
program names aren't accepted.
If "getOutput" is true, "output" will contain standard out and standard
error and "errOutput" will be "". If "getOutput" is "separate", then
"output" will contain standard out and "errOutput" will contain standard
error. If "getOutput" is false, then both "output" and "errOutput" will be
"".
Returns in "exitCode" the exit code of the command line. If any errors
occur in safeExecute itself, "exitCode" will be -1, and "output" and
"errOutput" will be:
getOuptut == "separate": "", <error message>
otherwise: <error message>, ""
------------------------------------------------------------------------------]]
function Util.safeExecute (commandLine, getOutput)
return Debug.callWithContext ("", function (context)
local outFile, errFile
context:addCleanupHandler (function ()
if outFile then LrFileUtils.delete (outFile) end
if errFile then LrFileUtils.delete (errFile) end
end)
if getOutput then
local uuid = LrUUID.generateUUID ()
outFile = child (getStandardFilePath ("temp"), uuid .. ".out")
commandLine = commandLine .. ' > "' .. outFile .. '"'
if getOutput == "separate" then
errFile = child (getStandardFilePath ("temp"), uuid .. ".err")
commandLine = commandLine .. ' 2>"' .. errFile .. '"'
else
commandLine = commandLine .. ' 2>&1'
end
end
if WIN_ENV then commandLine = '"' .. commandLine .. '"' end
local exitStatus = LrTasks.execute (commandLine)
local output, errOutput, success = "", ""
local function outputErr (file, output)
local err = string.format ("Couldn't read output:\n%s\n%s",
file, output)
if getOutput == "separate" then
return -1, "", err
else
return -1, err, ""
end
end
if outFile then
success, output = pcall (LrFileUtils.readFile, outFile)
if not success then return outputErr (outFile, output) end
end
if errFile then
success, errOutput = pcall (LrFileUtils.readFile, errFile)
if not success then return outputErr (errFile, errOutput) end
end
return exitStatus, output, errOutput
end) end
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