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# which
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Like the unix `which` utility.
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Finds the first instance of a specified executable in the PATH
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environment variable. Does not cache the results, so `hash -r` is not
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needed when the PATH changes.
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## USAGE
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```javascript
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var which = require('which')
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// async usage
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which('node', function (er, resolvedPath) {
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// er is returned if no "node" is found on the PATH
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// if it is found, then the absolute path to the exec is returned
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})
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// sync usage
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// throws if not found
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var resolved = which.sync('node')
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// if nothrow option is used, returns null if not found
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resolved = which.sync('node', {nothrow: true})
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// Pass options to override the PATH and PATHEXT environment vars.
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which('node', { path: someOtherPath }, function (er, resolved) {
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if (er)
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throw er
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console.log('found at %j', resolved)
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})
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```
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## CLI USAGE
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Same as the BSD `which(1)` binary.
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```
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usage: which [-as] program ...
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```
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## OPTIONS
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You may pass an options object as the second argument.
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- `path`: Use instead of the `PATH` environment variable.
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- `pathExt`: Use instead of the `PATHEXT` environment variable.
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- `all`: Return all matches, instead of just the first one. Note that
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this means the function returns an array of strings instead of a
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single string.
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