echo：等待标准输入，后面可以接字符串，也支持正则表达式
root@server:~# man echoSYNOPSISecho [SHORT-OPTION]... [STRING]...echo LONG-OPTION
示范：
root@server:~# echo $PATH/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/binroot@server:~# echo 'nameserver 114.114.114.114' >> /etc/resolv.conf root@server:~# cat /etc/resolv.conf # This file is managed by man:systemd-resolved(8). Do not edit.## This is a dynamic resolv.conf file for connecting local clients to the# internal DNS stub resolver of systemd-resolved. This file lists all# configured search domains.## Run "resolvectl status" to see details about the uplink DNS servers# currently in use.## Third party programs must not access this file directly, but only through the# symlink at /etc/resolv.conf. To manage man:resolv.conf(5) in a different way,# replace this symlink by a static file or a different symlink.## See man:systemd-resolved.service(8) for details about the supported modes of# operation for /etc/resolv.conf.nameserver 127.0.0.53options edns0 trust-adnameserver 114.114.114.114
screen：模拟多个窗口，窗口关闭后还可以调出来，常用于需要执行很长时间的时候
root@server:~# screen --helpUse: screen [-opts] [cmd [args]]or: screen -r [host.tty]Options:-4 Resolve hostnames only to IPv4 addresses.-6 Resolve hostnames only to IPv6 addresses.-a Force all capabilities into each window's termcap.-A -[r|R]Adapt all windows to the new display width & height.-c file Read configuration file instead of '.screenrc'.-d (-r) Detach the elsewhere running screen (and reattach here).-dmS nameStart as daemon: Screen session in detached mode.-D (-r) Detach and logout remote (and reattach here).-D -RR Do whatever is needed to get a screen session.-e xy Change command characters.-f Flow control on, -fn = off, -fa = auto.-h linesSet the size of the scrollback history buffer.-i Interrupt output sooner when flow control is on.-l Login mode on (update /var/run/utmp), -ln = off.-ls [match] or-list Do nothing, just list our SockDir [on possible matches].-L Turn on output logging.-Logfile file Set logfile name.-m ignore $STY variable, do create a new screen session.-O Choose optimal output rather than exact vt100 emulation.-p windowPreselect the named window if it exists.-q Quiet startup. Exits with non-zero return code if unsuccessful.-Q Commands will send the response to the stdout of the querying process.-r [session] Reattach to a detached screen process.-R Reattach if possible, otherwise start a new session.-s shellShell to execute rather than $SHELL.-S sockname Name this session <pid>.sockname instead of <pid>.<tty>.<host>.-t titleSet title. (window's name).-T term Use term as $TERM for windows, rather than "screen".-U Tell screen to use UTF-8 encoding.-v Print "Screen version 4.08.00 (GNU) 05-Feb-20".-wipe [match] Do nothing, just clean up SockDir [on possible matches].-x Attach to a not detached screen. (Multi display mode).-X Execute <cmd> as a screen command in the specified session.root@server:~# screen -lsThere is a screen on:9932.test (04/01/ 01:54:22 PM) (Detached)1 Socket in /run/screen/S-root.
date：显示系统时间
root@server:~# dateSun 03 Apr 10:33:57 PM UTCroot@server:~# date --helpUsage: date [OPTION]... [+FORMAT]or: date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]Display the current time in the given FORMAT, or set the system date.Mandatory arguments to long options are mandatory for short options too.-d, --date=STRINGdisplay time described by STRING, not 'now'--debugannotate the parsed date,and warn about questionable usage to stderr-f, --file=DATEFILE like --date; once for each line of DATEFILE-I[FMT], --iso-8601[=FMT] output date/time in ISO 8601 format.FMT='date' for date only (the default),'hours', 'minutes', 'seconds', or 'ns'for date and time to the indicated precision.Example: -08-14T02:34:56-06:00-R, --rfc-email output date and time in RFC 5322 format.Example: Mon, 14 Aug 02:34:56 -0600--rfc-3339=FMT output date/time in RFC 3339 format.FMT='date', 'seconds', or 'ns'for date and time to the indicated precision.Example: -08-14 02:34:56-06:00-r, --reference=FILE display the last modification time of FILE-s, --set=STRING set time described by STRING-u, --utc, --universalprint or set Coordinated Universal Time (UTC)--helpdisplay this help and exit--version output version information and exitFORMAT controls the output. Interpreted sequences are:%% a literal %%a locale's abbreviated weekday name (e.g., Sun)%A locale's full weekday name (e.g., Sunday)%b locale's abbreviated month name (e.g., Jan)%B locale's full month name (e.g., January)%c locale's date and time (e.g., Thu Mar 3 23:05:25 )%C century; like %Y, except omit last two digits (e.g., 20)%d day of month (e.g., 01)%D date; same as %m/%d/%y%e day of month, space padded; same as %_d%F full date; same as %Y-%m-%d%g last two digits of year of ISO week number (see %G)%G year of ISO week number (see %V); normally useful only with %V%h same as %b%H hour (00..23)%I hour (01..12)%j day of year (001..366)%k hour, space padded ( 0..23); same as %_H%l hour, space padded ( 1..12); same as %_I%m month (01..12)%M minute (00..59)%n a newline%N nanoseconds (000000000..999999999)%p locale's equivalent of either AM or PM; blank if not known%P like %p, but lower case%q quarter of year (1..4)%r locale's 12-hour clock time (e.g., 11:11:04 PM)%R 24-hour hour and minute; same as %H:%M%s seconds since 1970-01-01 00:00:00 UTC%S second (00..60)%t a tab%T time; same as %H:%M:%S%u day of week (1..7); 1 is Monday%U week number of year, with Sunday as first day of week (00..53)%V ISO week number, with Monday as first day of week (01..53)%w day of week (0..6); 0 is Sunday%W week number of year, with Monday as first day of week (00..53)%x locale's date representation (e.g., 12/31/99)%X locale's time representation (e.g., 23:13:48)%y last two digits of year (00..99)%Y year%z +hhmm numeric time zone (e.g., -0400)%:z +hh:mm numeric time zone (e.g., -04:00)%::z +hh:mm:ss numeric time zone (e.g., -04:00:00)%:::z numeric time zone with : to necessary precision (e.g., -04, +05:30)%Z alphabetic time zone abbreviation (e.g., EDT)By default, date pads numeric fields with zeroes.The following optional flags may follow '%':- (hyphen) do not pad the field_ (underscore) pad with spaces0 (zero) pad with zeros^ use upper case if possible# use opposite case if possibleAfter any flags comes an optional field width, as a decimal number;then an optional modifier, which is eitherE to use the locale's alternate representations if available, orO to use the locale's alternate numeric symbols if available.Examples:Convert seconds since the epoch (1970-01-01 UTC) to a date$ date --date='@2147483647'Show the time on the west coast of the US (use tzselect(1) to find TZ)$ TZ='America/Los_Angeles' dateShow the local time for 9AM next Friday on the west coast of the US$ date --date='TZ="America/Los_Angeles" 09:00 next Fri'GNU coreutils online help: </software/coreutils/>Full documentation at: </software/coreutils/date>or available locally via: info '(coreutils) date invocation'[root@localhost ~]# date Mon Apr 4 06:41:34 CST [root@localhost ~]# date +%F-04-04[root@localhost ~]# date +%T06:41:49
ifconfig：查看和配置系统的网络信息 （最小化安装的操作系统可能没有这个命令，需要装一下net-tools）
[root@localhost ~]# ifconfig docker0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255inet6 fe80::42:21ff:fe2f:e2c5 prefixlen 64 scopeid 0x20<link>ether 02:42:21:2f:e2:c5 txqueuelen 0 (Ethernet)RX packets 20709 bytes 5831411 (5.5 MiB)RX errors 0 dropped 0 overruns 0 frame 0TX packets 21889 bytes 35876509 (34.2 MiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0ens160: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500inet 192.168.20.4 netmask 255.255.255.0 broadcast 192.168.20.255inet6 fe80::f20d:3936:1627:5ceb prefixlen 64 scopeid 0x20<link>ether 00:50:56:94:37:2b txqueuelen 1000 (Ethernet)RX packets 3617156 bytes 3352893357 (3.1 GiB)RX errors 0 dropped 0 overruns 0 frame 0TX packets 1265033 bytes 57181152592 (53.2 GiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536inet 127.0.0.1 netmask 255.0.0.0inet6 ::1 prefixlen 128 scopeid 0x10<host>loop txqueuelen 1000 (Local Loopback)RX packets 170 bytes 24748 (24.1 KiB)RX errors 0 dropped 0 overruns 0 frame 0TX packets 170 bytes 24748 (24.1 KiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0veth43ef810: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500inet6 fe80::605e:b8ff:fe0a:763a prefixlen 64 scopeid 0x20<link>ether 62:5e:b8:0a:76:3a txqueuelen 0 (Ethernet)RX packets 0 bytes 0 (0.0 B)RX errors 0 dropped 0 overruns 0 frame 0TX packets 8 bytes 656 (656.0 B)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0veth61cd4c6: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500inet6 fe80::e46c:16ff:fe86:ebfd prefixlen 64 scopeid 0x20<link>ether e6:6c:16:86:eb:fd txqueuelen 0 (Ethernet)RX packets 9904 bytes 699251 (682.8 KiB)RX errors 0 dropped 0 overruns 0 frame 0TX packets 10081 bytes 17791016 (16.9 MiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0vethbd3077f: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500inet6 fe80::480e:69ff:fe44:7a9f prefixlen 64 scopeid 0x20<link>ether 4a:0e:69:44:7a:9f txqueuelen 0 (Ethernet)RX packets 7 bytes 574 (574.0 B)RX errors 0 dropped 0 overruns 0 frame 0TX packets 16 bytes 1272 (1.2 KiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0[root@localhost ~]# [root@localhost ~]# [root@localhost ~]# [root@localhost ~]# ifconfig -helpUsage:ifconfig [-a] [-v] [-s] <interface> [[<AF>] <address>][add <address>[/<prefixlen>]][del <address>[/<prefixlen>]][[-]broadcast [<address>]] [[-]pointopoint [<address>]][netmask <address>] [dstaddr <address>] [tunnel <address>][outfill <NN>] [keepalive <NN>][hw <HW> <address>] [mtu <NN>][[-]trailers] [[-]arp] [[-]allmulti][multicast] [[-]promisc][mem_start <NN>] [io_addr <NN>] [irq <NN>] [media <type>][txqueuelen <NN>][[-]dynamic][up|down] ...<HW>=Hardware Type.List of possible hardware types:loop (Local Loopback) slip (Serial Line IP) cslip (VJ Serial Line IP) slip6 (6-bit Serial Line IP) cslip6 (VJ 6-bit Serial Line IP) adaptive (Adaptive Serial Line IP) ash (Ash) ether (Ethernet) ax25 (AMPR AX.25) netrom (AMPR NET/ROM) rose (AMPR ROSE) tunnel (IPIP Tunnel) ppp (Point-to-Point Protocol) hdlc ((Cisco)-HDLC) lapb (LAPB) arcnet (ARCnet) dlci (Frame Relay DLCI) frad (Frame Relay Access Device) sit (IPv6-in-IPv4) fddi (Fiber Distributed Data Interface) hippi (HIPPI) irda (IrLAP) ec (Econet) x25 (generic X.25) infiniband (InfiniBand) eui64 (Generic EUI-64) <AF>=Address family. Default: inetList of possible address families:unix (UNIX Domain) inet (DARPA Internet) inet6 (IPv6) ax25 (AMPR AX.25) netrom (AMPR NET/ROM) rose (AMPR ROSE) ipx (Novell IPX) ddp (Appletalk DDP) ec (Econet) ash (Ash) x25 (CCITT X.25) [root@localhost ~]# ifconfig docker0 down #关闭docker网卡[root@localhost ~]# ifconfig docker0docker0: flags=4098<BROADCAST,MULTICAST> mtu 1500inet 172.17.0.1 netmask 255.255.0.0 broadcast 172.17.255.255ether 02:42:21:2f:e2:c5 txqueuelen 0 (Ethernet)RX packets 20709 bytes 5831411 (5.5 MiB)RX errors 0 dropped 0 overruns 0 frame 0TX packets 21889 bytes 35876509 (34.2 MiB)TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
export：可以显示当前bash的环境变量
[root@localhost ~]# exportdeclare -x CLASSPATH="/usr/local/java/jdk1.8.0_161/lib/"declare -x HISTCONTROL="ignoredups"declare -x HISTSIZE="1000"declare -x HOME="/root"declare -x HOSTNAME="localhost.localdomain"declare -x JAVA_HOME="/usr/local/java/jdk1.8.0_161"declare -x LANG="en_US.UTF-8"declare -x LESSOPEN="||/usr/bin/lesspipe.sh %s"declare -x LOGNAME="root"declare -x LS_COLORS="rs=0:di=01;34:ln=01;36:mh=00:pi=40;33:so=01;35:do=01;35:bd=40;33;01:cd=40;33;01:or=40;31;01:mi=01;05;37;41:su=37;41:sg=30;43:ca=30;41:tw=30;42:ow=34;42:st=37;44:ex=01;32:*.tar=01;31:*.tgz=01;31:*.arc=01;31:*.arj=01;31:*.taz=01;31:*.lha=01;31:*.lz4=01;31:*.lzh=01;31:*.lzma=01;31:*.tlz=01;31:*.txz=01;31:*.tzo=01;31:*.t7z=01;31:*.zip=01;31:*.z=01;31:*.Z=01;31:*.dz=01;31:*.gz=01;31:*.lrz=01;31:*.lz=01;31:*.lzo=01;31:*.xz=01;31:*.bz2=01;31:*.bz=01;31:*.tbz=01;31:*.tbz2=01;31:*.tz=01;31:*.deb=01;31:*.rpm=01;31:*.jar=01;31:*.war=01;31:*.ear=01;31:*.sar=01;31:*.rar=01;31:*.alz=01;31:*.ace=01;31:*.zoo=01;31:*.cpio=01;31:*.7z=01;31:*.rz=01;31:*.cab=01;31:*.jpg=01;35:*.jpeg=01;35:*.gif=01;35:*.bmp=01;35:*.pbm=01;35:*.pgm=01;35:*.ppm=01;35:*.tga=01;35:*.xbm=01;35:*.xpm=01;35:*.tif=01;35:*.tiff=01;35:*.png=01;35:*.svg=01;35:*.svgz=01;35:*.mng=01;35:*.pcx=01;35:*.mov=01;35:*.mpg=01;35:*.mpeg=01;35:*.m2v=01;35:*.mkv=01;35:*.webm=01;35:*.ogm=01;35:*.mp4=01;35:*.m4v=01;35:*.mp4v=01;35:*.vob=01;35:*.qt=01;35:*.nuv=01;35:*.wmv=01;35:*.asf=01;35:*.rm=01;35:*.rmvb=01;35:*.flc=01;35:*.avi=01;35:*.fli=01;35:*.flv=01;35:*.gl=01;35:*.dl=01;35:*.xcf=01;35:*.xwd=01;35:*.yuv=01;35:*.cgm=01;35:*.emf=01;35:*.axv=01;35:*.anx=01;35:*.ogv=01;35:*.ogx=01;35:*.aac=01;36:*.au=01;36:*.flac=01;36:*.mid=01;36:*.midi=01;36:*.mka=01;36:*.mp3=01;36:*.mpc=01;36:*.ogg=01;36:*.ra=01;36:*.wav=01;36:*.axa=01;36:*.oga=01;36:*.spx=01;36:*.xspf=01;36:"declare -x MAIL="/var/spool/mail/root"declare -x OLDPWDdeclare -x PATH="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/usr/local/java/jdk1.8.0_161/bin:/root/bin"declare -x PWD="/root"declare -x SHELL="/bin/bash"declare -x SHLVL="1"declare -x SSH_CLIENT="192.168.40.1 50881 22"declare -x SSH_CONNECTION="192.168.40.1 50881 192.168.20.5 22"declare -x SSH_TTY="/dev/pts/2"declare -x TERM="vt100"declare -x USER="root"declare -x XDG_RUNTIME_DIR="/run/user/0"declare -x XDG_SESSION_ID="485"[root@localhost ~]# export --help-bash: export: --: invalid optionexport: usage: export [-fn] [name[=value] ...] or export -p
