Linux head/tail命令详解程序员

head命令用于显示文件的开头的内容。在默认情况下，head命令显示文件的头10行内容。

tail命令用于显示文件的结尾的内容。在默认情况下，taild命令显示文件的后10行内容。

head常见命令参数

  -c, --bytes=[-]K         print the first K bytes of each file; 
                             with the leading `-', print all but the last 
                             K bytes of each file 
  -n, --lines=[-]K         print the first K lines instead of the first 10; 
                             with the leading `-', print all but the last 
                             K lines of each file 
  -q, --quiet, --silent    never print headers giving file names 
  -v, --verbose            always print headers giving file names 
      --help     display this help and exit 
      --version  output version information and exit

tail场景命令

 -c, --bytes=K            output the last K bytes; alternatively, use -c +K 
                           to output bytes starting with the Kth of each file 
  -f, --follow[={name|descriptor}] 
                           output appended data as the file grows; 
                           -f, --follow, and --follow=descriptor are 
                           equivalent 
  -F                       same as --follow=name --retry 
  -n, --lines=K            output the last K lines, instead of the last 10; 
                           or use -n +K to output lines starting with the Kth 
      --max-unchanged-stats=N 
                           with --follow=name, reopen a FILE which has not 
                           changed size after N (default 5) iterations 
                           to see if it has been unlinked or renamed 
                           (this is the usual case of rotated log files). 
                           With inotify, this option is rarely useful. 
      --pid=PID            with -f, terminate after process ID, PID dies 
  -q, --quiet, --silent    never output headers giving file names 
      --retry              keep trying to open a file even when it is or 
                             becomes inaccessible; useful when following by 
                             name, i.e., with --follow=name 
  -s, --sleep-interval=N   with -f, sleep for approximately N seconds 
                             (default 1.0) between iterations. 
                           With inotify and --pid=P, check process P at 
                           least once every N seconds. 
  -v, --verbose            always output headers giving file names 
      --help     display this help and exit 
      --version  output version information and exit

常用的命令展示

head :显示文件的前几行,默认10行   
head -n 2 /home/omd/h.txt 
	==>head -n 3 == head -3    可以直接跟行数 
cat h.txt | grep -v "hello"     过滤掉特定字符串，效率低，因为有管道 
	==>grep -v "hello" h.txt  可以直接跟文件名，效率快 
tail: 显示文件最后几行，默认10行 
tail -10 /home/omd/h.txt    显示最后10行 
tail -f /home/omd/h.txt     实时跟踪文件， 如果文件不存在，则终止  
tail -F /home/omd/h.txt     如果文件不存在，会继续尝试 
head -30 /home/omd/h.txt | tail -11 /home/omd/h.txt   输出一个文件的20-30行显示文件的前n行 
head -n 5 log2014.log输出文件除了最后n行的全部内容 
head -n -6 log2014.log从第5行开始显示文件 
tail -n +5 log2014.log    【显示文件的全部内容】 
tail -n 5  log2014.log    【只显示最后的5行】  根more/less差不多