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