linux cat more head tail 查看文本

ECS信息

• 规格：2vCPUs | 4GiB | kc1.large.2
• 镜像：openEuler 20.03 64bit with ARM | 公共镜像

linux cat more head tail 查看文本

cat 查看文本（带行号）

# cat ssh_config -n
     1	#	$OpenBSD: ssh_config,v 1.33 2017/05/07 23:12:57 djm Exp $
     2	
     3	# This is the ssh client system-wide configuration file.  See
     4	# ssh_config(5) for more information.  This file provides defaults for
     5	# users, and the values can be changed in per-user configuration files
     6	# or on the command line.
     7	
     8	# Configuration data is parsed as follows:
     9	#  1. command line options
    10	#  2. user-specific file
    11	#  3. system-wide file
    12	# Any configuration value is only changed the first time it is set.
    13	# Thus, host-specific definitions should be at the beginning of the
    14	# configuration file, and defaults at the end.
    15	
    16	# Site-wide defaults for some commonly used options.  For a comprehensive
    17	# list of available options, their meanings and defaults, please see the
    18	# ssh_config(5) man page.
    19	
    20	# Host *
    21	#   ForwardAgent no
    22	#   ForwardX11 no
    23	#   PasswordAuthentication yes
    24	#   HostbasedAuthentication no
    25	#   GSSAPIAuthentication no
    26	#   GSSAPIDelegateCredentials no
    27	#   GSSAPIKeyExchange no
    28	#   GSSAPITrustDNS no
    29	#   BatchMode no
    30	#   CheckHostIP yes
    31	#   AddressFamily any
    32	#   ConnectTimeout 0
    33	#   StrictHostKeyChecking ask
    34	#   IdentityFile ~/.ssh/id_rsa
    35	#   IdentityFile ~/.ssh/id_dsa
    36	#   IdentityFile ~/.ssh/id_ecdsa
    37	#   IdentityFile ~/.ssh/id_ed25519
    38	#   Port 22
    39	#   Protocol 2
    40	#   Ciphers aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc
    41	#   MACs hmac-md5,hmac-sha1,umac-64@openssh.com
    42	#   EscapeChar ~
    43	#   Tunnel no
    44	#   TunnelDevice any:any
    45	#   PermitLocalCommand no
    46	#   VisualHostKey no
    47	#   ProxyCommand ssh -q -W %h:%p gateway.example.com
    48	#   RekeyLimit 1G 1h
    49	#
    50	# To modify the system-wide ssh configuration, create a  *.conf  file under
    51	#  /etc/ssh/ssh_config.d/  which will be automatically included below
    52	Include /etc/ssh/ssh_config.d/*.conf

more 每屏显示指定行数的文本

more 可以滚动查看大文本
-5 的意思是 每屏显示5行
向下浏览是 z 或者 space
向上浏览是 b

# more -5 ssh_config
#	$OpenBSD: ssh_config,v 1.33 2017/05/07 23:12:57 djm Exp $

# This is the ssh client system-wide configuration file.  See
# ssh_config(5) for more information.  This file provides defaults for
# users, and the values can be changed in per-user configuration files
--More--(15%)

head 查看文本的前10行

# head -n 10 sshd_config 
#	$OpenBSD: sshd_config,v 1.103 2018/04/09 20:41:22 tj Exp $

# This is the sshd server system-wide configuration file.  See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/bin:/usr/bin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented.  Uncommented options override the

tail -f 循环读取ssh日志

# pwd
/var/log

# tail -f secure
Oct  2 22:52:37 ecs-4eee sshd[21279]: pam_unix(sshd:session): session closed for user root
Oct  2 22:52:37 ecs-4eee sshd[21344]: pam_unix(sshd:session): session closed for user root
Oct  2 22:55:38 ecs-4eee sshd[21438]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 22:55:38 ecs-4eee sshd[21503]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 22:56:33 ecs-4eee sshd[21438]: pam_unix(sshd:session): session closed for user root
Oct  2 22:56:33 ecs-4eee sshd[21503]: pam_unix(sshd:session): session closed for user root
Oct  2 23:09:18 ecs-4eee sshd[21605]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:09:19 ecs-4eee sshd[21670]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:09:27 ecs-4eee sshd[21605]: pam_unix(sshd:session): session closed for user root
Oct  2 23:09:27 ecs-4eee sshd[21670]: pam_unix(sshd:session): session closed for user root

此时再新建一个ssh会话，查看日志输出变化

# tail -f secure
Oct  2 22:52:37 ecs-4eee sshd[21279]: pam_unix(sshd:session): session closed for user root
Oct  2 22:52:37 ecs-4eee sshd[21344]: pam_unix(sshd:session): session closed for user root
Oct  2 22:55:38 ecs-4eee sshd[21438]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 22:55:38 ecs-4eee sshd[21503]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 22:56:33 ecs-4eee sshd[21438]: pam_unix(sshd:session): session closed for user root
Oct  2 22:56:33 ecs-4eee sshd[21503]: pam_unix(sshd:session): session closed for user root
Oct  2 23:09:18 ecs-4eee sshd[21605]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:09:19 ecs-4eee sshd[21670]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:09:27 ecs-4eee sshd[21605]: pam_unix(sshd:session): session closed for user root
Oct  2 23:09:27 ecs-4eee sshd[21670]: pam_unix(sshd:session): session closed for user root
Oct  2 23:10:34 ecs-4eee sshd[21740]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:10:34 ecs-4eee sshd[21805]: pam_unix(sshd:session): session opened for user root by (uid=0)

关闭新建的ssh会话，查看日志输出变化

# tail -f secure
Oct  2 22:52:37 ecs-4eee sshd[21279]: pam_unix(sshd:session): session closed for user root
Oct  2 22:52:37 ecs-4eee sshd[21344]: pam_unix(sshd:session): session closed for user root
Oct  2 22:55:38 ecs-4eee sshd[21438]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 22:55:38 ecs-4eee sshd[21503]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 22:56:33 ecs-4eee sshd[21438]: pam_unix(sshd:session): session closed for user root
Oct  2 22:56:33 ecs-4eee sshd[21503]: pam_unix(sshd:session): session closed for user root
Oct  2 23:09:18 ecs-4eee sshd[21605]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:09:19 ecs-4eee sshd[21670]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:09:27 ecs-4eee sshd[21605]: pam_unix(sshd:session): session closed for user root
Oct  2 23:09:27 ecs-4eee sshd[21670]: pam_unix(sshd:session): session closed for user root
Oct  2 23:10:34 ecs-4eee sshd[21740]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:10:34 ecs-4eee sshd[21805]: pam_unix(sshd:session): session opened for user root by (uid=0)
Oct  2 23:10:53 ecs-4eee sshd[21740]: pam_unix(sshd:session): session closed for user root
Oct  2 23:10:53 ecs-4eee sshd[21805]: pam_unix(sshd:session): session closed for user root

帮助文档（部分）

# cat --help
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: <https://www.gnu.org/software/coreutils/>
Full documentation <https://www.gnu.org/software/coreutils/cat>
or available locally via: info '(coreutils) cat invocation'

# more --help

Usage:
 more [options] <file>...

A file perusal filter for CRT viewing.

Options:
 -d          display help instead of ringing bell
 -f          count logical rather than screen lines
 -l          suppress pause after form feed
 -c          do not scroll, display text and clean line ends
 -p          do not scroll, clean screen and display text
 -s          squeeze multiple blank lines into one
 -u          suppress underlining
 -<number>   the number of lines per screenful
 +<number>   display file beginning from line number
 +/<string>  display file beginning from search string match

     --help     display this help
 -V, --version  display version

For more details see more(1).

# head --help
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.
Binary prefixes can be used, too: KiB=K, MiB=M, and so on.

GNU coreutils online help: <https://www.gnu.org/software/coreutils/>
Full documentation <https://www.gnu.org/software/coreutils/head>
or available locally via: info '(coreutils) head invocation'

# tail --help
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

......

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