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, "op": "recv", "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, "op": "recv", "ncc0": 82}

16:09:24.339 DEBUG http-80-81 hyjc.cometd.CometdServlet - { "cid": 1291283017076151, "op": "recv", "ncc0": 142}

16:09:24.360 DEBUG http-80-64 hyjc.cometd.CometdServlet - { "cid": 1291343201649090, "op": "recv", "ncc0": 40}

16:09:24.359 DEBUG http-80-143 hyjc.cometd.CometdServlet - { "cid": 1291283017076176, "op": "recv", "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 faith@acm.org

* Copyright 1996, 2003 Rickard E. Faith (faith@acm.org)

*

* 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

#include

#include

#include

#include

//#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

while (fgets(buffer[tail], BUFSIZ, str)) {

if (++tail >= lines) {

tail = 0;

head = 1;

}

}

if (head) {

for (i = tail; i

for (i = 0; i

} else {

for (i = head; i

}

fflush(stdout);

for (i = 0; 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, "r"))) {

fprintf(stderr, _("Cannot open \"%s\" for read\n"), filename);

perror(argv[0]);

exit(1);

}

if (!fseek(str, osize, SEEK_SET))

while ((count = fread(buffer, 1, sizeof(buffer), str)) > 0)

fwrite(buffer, 1, 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]#

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