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'use strict';
var fs = require('fs');
var LRU = require('lru-cache');
var shebangCommand = require('shebang-command');
var shebangCache = new LRU({ max: 50, maxAge: 30 * 1000 }); // Cache just for 30sec
function readShebang(command) {
var buffer;
var fd;
var shebang;
// Check if it is in the cache first
if (shebangCache.has(command)) {
return shebangCache.get(command);
}
// Read the first 150 bytes from the file
buffer = new Buffer(150);
try {
fd = fs.openSync(command, 'r');
fs.readSync(fd, buffer, 0, 150, 0);
fs.closeSync(fd);
} catch (e) { /* empty */ }
// Attempt to extract shebang (null is returned if not a shebang)
shebang = shebangCommand(buffer.toString());
// Store the shebang in the cache
shebangCache.set(command, shebang);
return shebang;
}
module.exports = readShebang;
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