C# txt文本读取最后X行

来源：互联网发布：ubuntu文件夹进入终端编辑：程序博客网时间：2024/05/17 20:26
using System.IO;/// <summary>/// 读取文本文件最后的内容/// </summary>/// <param name="AFileName">文件名</param>/// <param name="ALineCount">行数</param>/// <param name="AEncoding">字符编码</param>/// <returns>返回读取的内容</returns>public string ReadLastLine(string AFileName, int ALineCount, Encoding AEncoding){    if (ALineCount <= 0) return string.Empty;    if (!File.Exists(AFileName)) return string.Empty; // 文件不存在    if (AEncoding == null) AEncoding = Encoding.Default;    using (FileStream vFileStream = new FileStream(AFileName,        FileMode.Open, FileAccess.Read, FileShare.Read))    {        if (vFileStream.Length <= 0) return string.Empty; // 空文件        byte[] vBuffer = new byte[0x1000]; // 缓冲区        int vReadLength; // 读取到的大小        int vLineCount = 0; // 读取的行数        int vReadCount = 0; // 读取的次数        int vScanCount = 0; // 扫描过的字符数        long vOffset = 0; // 向后读取的位置        do        {            vOffset = vBuffer.Length * ++vReadCount;            int vSpace = 0; // 偏移超出的空间            if (vOffset >= vFileStream.Length) // 超出范围            {                vSpace = (int)(vOffset - vFileStream.Length);                vOffset = vFileStream.Length;            }            vFileStream.Seek(-vOffset, SeekOrigin.End); //“SeekOrigin.End”反方向偏移读取位置            vReadLength = vFileStream.Read(vBuffer, 0, vBuffer.Length - vSpace);            #region 所读的缓冲里有多少行            for (int i = vReadLength - 1; i >= 0; i--)            {                if (vBuffer[i] == 10)                {                    if (vScanCount > 0) vLineCount++; // #13#10为回车换行                    if (vLineCount >= ALineCount) break;                }                vScanCount++;            }            #endregion 所读的缓冲里有多少行        } while (vReadLength >= vBuffer.Length && vOffset < vFileStream.Length &&             vLineCount < ALineCount);        if (vReadCount > 1) // 读的次数超过一次，则需重分配缓冲区        {            vBuffer = new byte[vScanCount];            vFileStream.Seek(-vScanCount, SeekOrigin.End);            vReadLength = vFileStream.Read(vBuffer, 0, vBuffer.Length);        }        return AEncoding.GetString(vBuffer, vReadLength - vScanCount, vScanCount);    }}private void button1_Click(object sender, EventArgs e){    textBox1.Text = ReadLastLine(@"c:\temp\WindowsUpdate.log", 7, Encoding.Default);}
以上代码转载于http://bbs.csdn.net/topics/230002962，31楼
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