1# which 2 3Like the unix `which` utility. 4 5Finds the first instance of a specified executable in the PATH 6environment variable. Does not cache the results, so `hash -r` is not 7needed when the PATH changes. 8 9## USAGE 10 11```javascript 12var which = require('which') 13 14// async usage 15which('node', function (er, resolvedPath) { 16 // er is returned if no "node" is found on the PATH 17 // if it is found, then the absolute path to the exec is returned 18}) 19 20// sync usage 21// throws if not found 22var resolved = which.sync('node') 23 24// if nothrow option is used, returns null if not found 25resolved = which.sync('node', {nothrow: true}) 26 27// Pass options to override the PATH and PATHEXT environment vars. 28which('node', { path: someOtherPath }, function (er, resolved) { 29 if (er) 30 throw er 31 console.log('found at %j', resolved) 32}) 33``` 34 35## CLI USAGE 36 37Same as the BSD `which(1)` binary. 38 39``` 40usage: which [-as] program ... 41``` 42 43## OPTIONS 44 45You may pass an options object as the second argument. 46 47- `path`: Use instead of the `PATH` environment variable. 48- `pathExt`: Use instead of the `PATHEXT` environment variable. 49- `all`: Return all matches, instead of just the first one. Note that 50 this means the function returns an array of strings instead of a 51 single string. 52