# 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.