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