原文链接：http://codingstandards.iteye.com/blog/832760 （转载请注明出处）
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。
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。
[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]#
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 <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, "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]#
tailf.zip (3.4 KB)下载次数: 16
