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@soldair
Created August 26, 2015 21:40
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read the end of a file
var fs = require('fs')
// usage example:
// var t = require('./this-file.js')
// t('/var/log/boot.log',1024,function(err,data){ console.log(data+'')})
//
module.exports = function(file,lastNBytes,cb){
var fd, size, called
var orig = cb
var start = function fn(err,data){
if(steps.length && !err) {
return steps.shift(next)
}
if(called) return;
called = 1
orig(err,data)
if(fd) fs.close(fd,function(){})
}
var steps = [
// first open the file
function(next){
fs.open(file,'r',function(err,_fd){
if(err) return cb(err)
fd = _fd
next()
})
},
// then stat the file to get the size
function(next){
fs.stat(file,function(err,stat){
if(err) return cb(err)
size = stat.size
next()
})
},
// read the file offset you want and close the file
function (next){
fs.read(fd, new Buffer(lastNBytes), size-lastNBytes, lastNBytes, 0, function(err,bytesRead,data){
if(err) return next(err)
next(false,data.slice(0,bytesRead))
})
}
]
start();
}
@makamekm
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makamekm commented Apr 17, 2020

Sorry, but this code does not work, because next is undefined for var start.

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