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PR-URL: https://github.com/nodejs/node/pull/3310 Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
41 lines
1.3 KiB
Markdown
41 lines
1.3 KiB
Markdown
# debuglog - backport of util.debuglog() from node v0.11
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To facilitate using the `util.debuglog()` function that will be available when
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node v0.12 is released now, this is a copy extracted from the source.
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## require('debuglog')
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Return `util.debuglog`, if it exists, otherwise it will return an internal copy
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of the implementation from node v0.11.
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## debuglog(section)
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* `section` {String} The section of the program to be debugged
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* Returns: {Function} The logging function
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This is used to create a function which conditionally writes to stderr
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based on the existence of a `NODE_DEBUG` environment variable. If the
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`section` name appears in that environment variable, then the returned
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function will be similar to `console.error()`. If not, then the
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returned function is a no-op.
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For example:
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```javascript
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var debuglog = util.debuglog('foo');
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var bar = 123;
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debuglog('hello from foo [%d]', bar);
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```
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If this program is run with `NODE_DEBUG=foo` in the environment, then
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it will output something like:
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FOO 3245: hello from foo [123]
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where `3245` is the process id. If it is not run with that
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environment variable set, then it will not print anything.
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You may separate multiple `NODE_DEBUG` environment variables with a
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comma. For example, `NODE_DEBUG=fs,net,tls`.
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