DDR爱好者之家 Design By 杰米

linux系统内置命令可以通过以下两种方式查询:“cat --help” 或者“man cat”。

cat命令的常用选项和官方解释如下:

cat file_name 显示文件全部内容

cat -b file_name 显示文件非空行内容

cat -E file_name 在文件每行末尾显示$,常用于管道功能

cat -n file_name 显示内容和行号

Usage: cat [OPTION]... [FILE]...
Concatenate FILE(s) to standard output.

With no FILE, or when FILE is -, read standard input.

 -A, --show-all      equivalent to -vET
 -b, --number-nonblank  number nonempty output lines, overrides -n
 -e            equivalent to -vE
 -E, --show-ends     display $ at end of each line
 -n, --number       number all output lines
 -s, --squeeze-blank   suppress repeated empty output lines
 -t            equivalent to -vT
 -T, --show-tabs     display TAB characters as ^I
 -u            (ignored)
 -v, --show-nonprinting  use ^ and M- notation, except for LFD and TAB
   --help   display this help and exit
   --version output version information and exit

Examples:
 cat f - g Output f's contents, then standard input, then g's contents.
 cat    Copy standard input to standard output.

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: http://www.gnu.org/software/coreutils/cat

head命令及其选项如下:

head -c10 file_name 显示一开始的10个字节

head -c-10 file_name 显示除末尾10个字节之外的内容

head -n10 file_name 显示一开始的10行内容

head -n-10 file_name 显示除末尾的10行之外的内容

Usage: head [OPTION]... [FILE]...
Print the first 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.

With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
 -c, --bytes=[-]NUM    print the first NUM bytes of each file;
               with the leading '-', print all but the last
               NUM bytes of each file
 -n, --lines=[-]NUM    print the first NUM lines instead of the first 10;
               with the leading '-', print all but the last
               NUM lines of each file
 -q, --quiet, --silent  never print headers giving file names
 -v, --verbose      always print headers giving file names
 -z, --zero-terminated  line delimiter is NUL, not newline
   --help   display this help and exit
   --version output version information and exit

NUM may have a multiplier suffix:
b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,
GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: http://www.gnu.org/software/coreutils/head

tail命令及其选项如下:

tail -c10 file_name 显示末尾的10个字节

tail -c-10 file_name 显示除开头10个字节之外的内容

tail -n10 file_name 显示末尾的10行内容

tail -n-10 file_name 显示除开头的10行之外的内容

Usage: tail [OPTION]... [FILE]...
Print the last 10 lines of each FILE to standard output.
With more than one FILE, precede each with a header giving the file name.

With no FILE, or when FILE is -, read standard input.

Mandatory arguments to long options are mandatory for short options too.
 -c, --bytes=[+]NUM    output the last NUM bytes; or use -c +NUM to
               output starting with byte NUM of each file
 -f, --follow[={name|descriptor}]
              output appended data as the file grows;
               an absent option argument means 'descriptor'
 -F            same as --follow=name --retry
 -n, --lines=[+]NUM    output the last NUM lines, instead of the last 10;
               or use -n +NUM to output starting with line NUM
   --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 if it is inaccessible
 -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
 -z, --zero-terminated  line delimiter is NUL, not newline
   --help   display this help and exit
   --version output version information and exit

NUM may have a multiplier suffix:
b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024,
GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y.

With --follow (-f), tail defaults to following the file descriptor, which
means that even if a tail'ed file is renamed, tail will continue to track
its end. This default behavior is not desirable when you really want to
track the actual name of the file, not the file descriptor (e.g., log
rotation). Use --follow=name in that case. That causes tail to track the
named file in a way that accommodates renaming, removal and creation.

GNU coreutils online help: <http://www.gnu.org/software/coreutils/>
Full documentation at: http://www.gnu.org/software/coreutils/tail

搭配管道使用更佳

此外,这三个命令常常与管道功能搭配,用于文件内容的操作,例如:

对data.txt中的数据进行排序:cat data.txt | sort

对data.txt中的内容匹配:cat data.txt | grep 'a'

输出data.txt中的非空行数:cat -b data.txt | wc -l

总结

DDR爱好者之家 Design By 杰米
广告合作:本站广告合作请联系QQ:858582 申请时备注:广告合作(否则不回)
免责声明:本站资源来自互联网收集,仅供用于学习和交流,请遵循相关法律法规,本站一切资源不代表本站立场,如有侵权、后门、不妥请联系本站删除!
DDR爱好者之家 Design By 杰米

《魔兽世界》大逃杀!60人新游玩模式《强袭风暴》3月21日上线

暴雪近日发布了《魔兽世界》10.2.6 更新内容,新游玩模式《强袭风暴》即将于3月21 日在亚服上线,届时玩家将前往阿拉希高地展开一场 60 人大逃杀对战。

艾泽拉斯的冒险者已经征服了艾泽拉斯的大地及遥远的彼岸。他们在对抗世界上最致命的敌人时展现出过人的手腕,并且成功阻止终结宇宙等级的威胁。当他们在为即将于《魔兽世界》资料片《地心之战》中来袭的萨拉塔斯势力做战斗准备时,他们还需要在熟悉的阿拉希高地面对一个全新的敌人──那就是彼此。在《巨龙崛起》10.2.6 更新的《强袭风暴》中,玩家将会进入一个全新的海盗主题大逃杀式限时活动,其中包含极高的风险和史诗级的奖励。

《强袭风暴》不是普通的战场,作为一个独立于主游戏之外的活动,玩家可以用大逃杀的风格来体验《魔兽世界》,不分职业、不分装备(除了你在赛局中捡到的),光是技巧和战略的强弱之分就能决定出谁才是能坚持到最后的赢家。本次活动将会开放单人和双人模式,玩家在加入海盗主题的预赛大厅区域前,可以从强袭风暴角色画面新增好友。游玩游戏将可以累计名望轨迹,《巨龙崛起》和《魔兽世界:巫妖王之怒 经典版》的玩家都可以获得奖励。