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