stderr

What are “cerr” and “stderr”?

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cerr is the C++ stream and stderr is the C file handle, both representing the standard error output. You write to them the same way you write to other streams and file handles: cerr << “Urk!\n”; fprintf (stderr, “Urk!\n”); I’m not sure what you mean by “recover” in this context, the output goes to standard … Read more

multiprocessing: How can I ʀᴇʟɪᴀʙʟʏ redirect stdout from a child process?

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The solution you suggest is a good one: create your processes manually such that you have explicit access to their stdout/stderr file handles. You can then create a socket to communicate with the sub-process and use multiprocessing.connection over that socket (multiprocessing.Pipe creates the same type of connection object, so this should give you all the … Read more

What method should I use to write error messages to ‘stderr’ using ‘printf’ in a bash script?

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First, yes, 1>&2 is the right thing to do. Second, the reason your 1>&2 2>errors.txt example doesn’t work is because of the details of exactly what redirection does. 1>&2 means “make filehandle 1 point to wherever filehandle 2 does currently” — i.e. stuff that would have been written to stdout now goes to stderr. 2>errors.txt … Read more

How can I display a ‘naked’ error message in PowerShell without an accompanying stacktrace?

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Preface re what doesn’t work: Setting the $ErrorView preference variable $ErrorView variable to ‘CategoryView’ causes PowerShell to output concise, single-line error representations instead, but this representation may not always include enough information, because the error message is typically not included; on the plus side, the text passed to Throw “…” is reflected, but, by contrast, … Read more

Python read from subprocess stdout and stderr separately while preserving order

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The code in your question may deadlock if the child process produces enough output on stderr (~100KB on my Linux machine). There is a communicate() method that allows to read from both stdout and stderr separately: from subprocess import Popen, PIPE process = Popen(command, stdout=PIPE, stderr=PIPE) output, err = process.communicate() If you need to read … Read more

How to debug “FastCGI sent in stderr: Primary script unknown while reading response header from upstream” and find the actual error message?

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To answer your question: in php-fpm.d/www.conf file: set the access.log entry: access.log = /var/log/$pool.access.log restart php-fpm service. try to access your page cat /var/log/www.access.log, you will see access logs like: – – 10/Nov/2016:19:02:11 +0000 “GET /app.php” 404 – – 10/Nov/2016:19:02:37 +0000 “GET /app.php” 404 To resolve “Primary script unknown” problem: if you see “GET /” … Read more

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