//从文件中提取文件指从x行到y行的内容 
//awk -v start=5 -v end=10 -F "\x01" '{if(NR>=start && NR<=end)print $1,NR}' app_v2.csv

var exec = require('child_process').exec;

var fs = require('fs');

var shell = {};

shell.getContentFromFile = function(file, pageIndex, pageSize, split, next) {

    fs.exists(file, function(exists) {

        if (!exists) {

            next('file not exist'+file, null, null);

        }

        var start = (pageIndex - 1) * pageSize + 1;

        var end = (pageIndex) * pageSize;

        var cmd = "gzip -d -c " + file + " | awk -v start=" + start + " -v end=" + end + " -F " + split + " '{ if(NR>=start && NR<=end) print $0}' ";

        console.log(" the awk: " + cmd);

        exec(cmd, function(err, stdout, stderr) {

            if (err) {

                console.log(err);

            }

            next(err, stdout, stderr);

        });

    });

};

shell.getFileLineCount = function(file, next) {

    fs.exists(file, function(exists) {

        if (!exists) {

              next('file not exist'+file, null, null);

        }

        var cmd = "gzip -d -c " + file + " | cat | wc -l";

        exec(cmd, next);

    });

};

module.exports = shell;