less 工具也是对文件或其它输出进行分页显示的工具，应该说是linux正统查看文件内容的工具，功能极其强大。less 的用法比起 more 更加的有弹性。使用less 时，可以使用 [pageup] [pagedown] 等按键的功能来往前往后翻看文件，更容易用来查看一个文件的内容！除此之外，在 less 中可以拥有更多的搜索功能。
/* 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 staticsize_tfilesize(constchar *filename) { structstatsb; if (!stat(filename, &sb)) return sb.st_size; return0; } staticvoidtailf(constchar *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); } intmain(int argc, char **argv) { char buffer[BUFSIZ]; size_t osize, nsize; FILE *str; constchar *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 */ } return0; }
