Centos tailf命令

我使用过的Linux命令之tailf - 跟踪日志文件/更好的tail -f版本

用途说明

　　tailf命令几乎等同于tail -f，严格说来应该与tail --follow=name更相似些。当文件改名之后它也能继续跟踪，特别适合于日志文件的跟踪（follow the growth of a log file）。与tail -f不同的是，如果文件不增长，它不会去访问磁盘文件（It is similar to tail -f but does not access the file when it is not growing. This has the side effect of not updating the access time for the file,so a filesystem flush does not occur periodically when no log activity is happening.）。tailf特别适合那些便携机上跟踪日志文件，因为它能省电，因为减少了磁盘访问嘛（tailf is extremely useful for monitoring log files on a laptop when logging is infrequent and the user desires that the hard disk spin down to conserve battery life.）。tailf命令不是个脚本，而是一个用C代码编译后的二进制执行文件，某些Linux安装之后没有这个命令，本文提供了怎么编译安装tailf命令的方法。

常用参数

格式：tailf logfile

动态跟踪日志文件logfile，最初的时候打印文件的最后10行内容。

使用示例

示例一 使用tailf命令跟踪日志

[root@web imx_server]#tailf log/WEB.LOG
"seq": 5710,
"clientId": 1291343201649254,
"presenceStatus": "1"
} }})
16:09:21.324 DEBUG http-80-79 hyjc.cometd.CometdServlet - { "cid": 1291343201649002,"op": "recv","ncc0": 175}
16:09:21.444 DEBUG http-80-32 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:21.506 DEBUG http-80-79 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:23.239 DEBUG http-80-45 hyjc.cometd.CometdServlet - { "cid": 1291343201649184,"ncc0": 55}
16:09:23.327 DEBUG http-80-45 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:24.288 DEBUG http-80-145 hyjc.cometd.CometdServlet - { "cid": 1291283017076175,"ncc0": 82}
16:09:24.339 DEBUG http-80-81 hyjc.cometd.CometdServlet - { "cid": 1291283017076151,"ncc0": 142}
16:09:24.360 DEBUG http-80-64 hyjc.cometd.CometdServlet - { "cid": 1291343201649090,"ncc0": 40}
16:09:24.359 DEBUG http-80-143 hyjc.cometd.CometdServlet - { "cid": 1291283017076176,"ncc0": 66}
16:09:24.878 DEBUG http-80-145 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:24.892 DEBUG http-80-143 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:24.896 DEBUG http-80-64 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:24.906 DEBUG http-80-81 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:25.095 DEBUG http-80-115 hyjc.filter.AccessCounterFilter - uri=/imx/cometd/service
16:09:25.095 DEBUG http-80-115 hyjc.cometd.CometdServlet - msgType IMX_ACTIVE_TEST msgBody {"clientId":1291343201649002,"presenceStatus":"1","seq":385}
16:09:25.095 INFO http-80-115 imx.client.ImxClient - Tx IMX_ACTIVE_TEST{seq=5711,client_id=1291343201649002,presence_status=1(presence_status_online),}
16:09:25.095 DEBUG http-80-115 hyjc.cometd.CometdServlet - { "cid": 1291343201649002,"op": "send","sent": 0,"rc": 1,"msg": { "mt": "IMX_ACTIVE_TEST","mb": {
"seq": 5711,
"clientId": 1291343201649002,
"presenceStatus": "1"
} }}
Ctrl+C
[root@web imx_server]#

示例二 编译安装tailf命令

有些Linux版本不带tailf命令的。

[root@smsgw root]#tailf
-bash: tailf: command not found
[root@smsgw root]#

到代码搜索网站www.koders.com输入tailf.c就可以搜索到源代码

tailf.c结果页面：http://www.koders.com/default.aspx?s=tailf.c&submit=Search&la=*&li=*

tailf.c源码页面：http://www.koders.com/c/fidB6EFAC156A7B4C4A46B38039C79B4AD34939EED0.aspx?s=tailf#L1

点左上角的download就可下载，也可直接下载本文附件tailf.zip。

[root@smsgw tailf]#unzip tailf.zip
Archive: tailf.zip
inflating: tailf.c
[root@smsgw tailf]#ls
tailf.c tailf.zip
[root@smsgw tailf]#gcc -o /usr/bin/tailf tailf.c
tailf.c:34:17: nls.h: 没有那个文件或目录
tailf.c: In function `tailf':
tailf.c:53: warning: passing arg 2 of `fprintf' makes pointer from integer without a cast
tailf.c: In function `main':
tailf.c:88: `LC_ALL' undeclared (first use in this function)
tailf.c:88: (Each undeclared identifier is reported only once
tailf.c:88: for each function it appears in.)
tailf.c:89: `PACKAGE' undeclared (first use in this function)
tailf.c:89: `LOCALEDIR' undeclared (first use in this function)
tailf.c:93: warning: passing arg 2 of `fprintf' makes pointer from integer without a cast
tailf.c:105: warning: passing arg 2 of `fprintf' makes pointer from integer without a cast
[root@smsgw tailf]#

修改一下tailf.c的源代码。

第34行附近：注释掉头文件，增加宏定义

//#include "nls.h"
#define _(s) s

第89行附近：把原来的代码注释掉

//setlocale(LC_ALL,"");
//bindtextdomain(PACKAGE,LOCALEDIR);
//textdomain(PACKAGE);

看了源代码之后，你是不是发现其实Linux命令其实并不太神秘。

注：本文附件中的tailf.c已经修改成下面的样子。

C代码

/* tailf.c -- tail a log file and then follow it * Created: Tue Jan 9 15:49:21 1996 by [email protected] * copyright 1996,2003 Rickard E. Faith ([email protected]) * * Permission is hereby granted,free of charge,to any person obtaining a * copy of this software and associated documentation files (the "Software"),* to deal in the Software without restriction,including without limitation * the rights to use,copy,modify,merge,publish,distribute,sublicense,* and/or sell copies of the Software,and to permit persons to whom the * Software is furnished to do so,subject to the following conditions: * * The above copyright notice and this permission notice shall be included * in all copies or substantial portions of the Software. * * THE SOFTWARE IS PROVIDED "AS IS",WITHOUT WARRANTY OF ANY KIND,EXPRESS OR * IMPLIED,INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,* fitness FOR A PARTIculaR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL * THE AUTHORS OR copYRIGHT HOLDERS BE LIABLE FOR ANY CLaim,damAGES OR * OTHER LIABILITY,WHETHER IN AN ACTION OF CONTRACT,TORT OR OTHERWISE,* ARISING FROM,OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR * OTHER DEALINGS IN THE SOFTWARE. * * less -F and tail -f cause a disk access every five seconds. This * program avoids this problem by waiting for the file size to change. * Hence,the file is not accessed,and the access time does not need to be * flushed back to disk. This is sort of a "stealth" tail. */ #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <malloc.h> #include <sys/stat.h> //#include "nls.h" #define _(s) s static size_t filesize(const char *filename) { struct stat sb; if (!stat(filename,&sb)) return sb.st_size; return 0; } static void tailf(const char *filename,int lines) { char **buffer; int head = 0; int tail = 0; FILE *str; int i; if (!(str = fopen(filename,"r"))) { fprintf(stderr,_("Cannot open \"%s\" for read\n"),filename); perror(""); exit(1); } buffer = malloc(lines * sizeof(*buffer)); for (i = 0; i < lines; i++) buffer[i] = malloc(BUFSIZ + 1); while (fgets(buffer[tail],BUFSIZ,str)) { if (++tail >= lines) { tail = 0; head = 1; } } if (head) { for (i = tail; i < lines; i++) fputs(buffer[i],stdout); for (i = 0; i < tail; i++) fputs(buffer[i],stdout); } else { for (i = head; i < tail; i++) fputs(buffer[i],stdout); } fflush(stdout); for (i = 0; i < lines; i++) free(buffer[i]); free(buffer); } int main(int argc,char **argv) { char buffer[BUFSIZ]; size_t osize,nsize; FILE *str; const char *filename; int count; //setlocale(LC_ALL,""); //bindtextdomain(PACKAGE,LOCALEDIR); //textdomain(PACKAGE); if (argc != 2) { fprintf(stderr,_("Usage: tailf logfile\n")); exit(1); } filename = argv[1]; tailf(filename,10); for (osize = filesize(filename);;) { nsize = filesize(filename); if (nsize != osize) { if (!(str = fopen(filename,filename); perror(argv[0]); exit(1); } if (!fseek(str,osize,SEEK_SET)) while ((count = fread(buffer,1,sizeof(buffer),str)) > 0) fwrite(buffer,count,stdout); fflush(stdout); fclose(str); osize = nsize; } usleep(250000); /* 250mS */ } return 0; } 

[root@smsgw tailf]#gcc -Wall -o /usr/bin/tailf tailf.c
[root@smsgw tailf]#tailf
Usage: tailf logfile
[root@smsgw tailf]#