一、常見(jiàn)Linux的發(fā)行版有哪些？不同發(fā)行版之間的聯(lián)系與區(qū)別
★debian：ubuntu，mint
★slackware:SUSE Linux Enterprise Server (SLES)，OpenSuse桌面
★redhat: Red Hat Enterprise，每18個(gè)月發(fā)行一個(gè)新版本
? ? ? ? ? ? ? ?CentOS，兼容RHEL的格式
? ? ? ? ? ? ? ?中標(biāo)麒麟，中標(biāo)軟件
? ? ? ? ? ? ? ?Fedora，每6個(gè)月發(fā)行一個(gè)新版本
★ArchLinux：輕量簡(jiǎn)潔
★Gentoo：極致性能，不提供傳統(tǒng)意義的安裝程序
★L(fēng)FS: Linux From scratch 自制Linux
★Android: kernel+busybox（工具集）+java虛擬機(jī)
聯(lián)系
★都使用Linux內(nèi)核
★發(fā)行版本號(hào)命名規(guī)則：主版本號(hào).次版本號(hào).末版本號(hào).打包版本號(hào).廠商版本號(hào)
★需遵守GNU通用公共許可協(xié)議
區(qū)分
★發(fā)行版有的是合作組織來(lái)維護(hù)，有的是企業(yè)公司來(lái)維護(hù)。例如前者有debian，后者有redhat
★發(fā)行版使用的軟件包管理器有可能不同。例如debian使用dpkg作為軟件包管理器，應(yīng)用程序管理器為apt-get。redhat使用rpm作為軟件包管理器，應(yīng)用程序管理器為yum。SUSE使用rpm作為軟件包管理器，應(yīng)用程序管理器為zypper。
參考鏈接：https://www.cnblogs.com/otosis/p/5914102.html
下圖來(lái)源網(wǎng)站?https://futurist.se/gldt/2012/10/29/gnulinux-distribution-timeline-12-10/
二、打印顯示當(dāng)前時(shí)間，格式是：20181209211008
要求格式為：年月日時(shí)分秒 即：CCYYMMDDhhmmss
man date 查閱date的manual幫助得知
????date [OPTION]... [+FORMAT]
????%Y year
????%m month (01..12)
????%d day of month (e.g., 01)
????%H hour (00..23)
? ??%M minute (00..59)
? ?? %S second (00..60)
因此得出?date +%Y%m%d%H%M%S
后附查閱到的date的manual幫助
NAME
? ? ? date - print or set the system date and time
SYNOPSIS
? ? ? date [OPTION]... [+FORMAT]
? ? ? date [-u|--utc|--universal] [MMDDhhmm[[CC]YY][.ss]]
DESCRIPTION
? ? ? 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=STRING
? ? ? ? ? ? ? display time described by STRING, not 'now'
? ? ? -f, --file=DATEFILE
? ? ? ? ? ? ? like --date once for each line of DATEFILE
? ? ? -I[TIMESPEC], --iso-8601[=TIMESPEC]
? ? ? ? ? ? ? output date/time in ISO 8601 format.? TIMESPEC='date' for date only (the default), 'hours', 'minutes', 'seconds', or 'ns' for date and time to the indicated precision.
? ? ? -r, --reference=FILE
? ? ? ? ? ? ? display the last modification time of FILE
? ? ? -R, --rfc-2822
? ? ? ? ? ? ? output date and time in RFC 2822 format.? Example: Mon, 07 Aug 2006 12:34:56 -0600
? ? ? --rfc-3339=TIMESPEC
? ? ? ? ? ? ? output? date and time in RFC 3339 format.? TIMESPEC='date', 'seconds', or 'ns' for date and time to the indicated precision.? Date and time components are separated by
? ? ? ? ? ? ? a single space: 2006-08-07 12:34:56-06:00
? ? ? -s, --set=STRING
? ? ? ? ? ? ? set time described by STRING
? ? ? -u, --utc, --universal
? ? ? ? ? ? ? print or set Coordinated Universal Time (UTC)
? ? ? --help display this help and exit
? ? ? --version
? ? ? ? ? ? ? output version information and exit
? ? ? FORMAT 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 2005)
? ? ? %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
? ? ? %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 spaces
? ? ? 0? ? ? (zero) pad with zeros
? ? ? ^? ? ? use upper case if possible
? ? ? #? ? ? use opposite case if possible
? ? ? After any flags comes an optional field width, as a decimal number; then an optional modifier, which is either E to use the locale's alternate representations? if? available,
? ? ? or O to use the locale's alternate numeric symbols if available.
ENVIRONMENT
? ? ? TZ? ? Specifies the timezone, unless overridden by command line parameters.? If neither is specified, the setting from /etc/localtime is used.
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' date
? ? ? Show 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: <http://www.gnu.org/software/coreutils/> Report date translation bugs to <http://translationproject.org/team/>
DATE STRING
? ? ? The? --date=STRING? is? a? mostly? free? format human readable date string such as "Sun, 29 Feb 2004 16:21:42 -0800" or "2004-02-29 16:21:42" or even "next Thursday".? A date
? ? ? string may contain items indicating calendar date, time of day, time zone, day of week, relative time, relative date, and numbers.? An empty string indicates the beginning of
? ? ? the day.? The date string format is more complex than is easily documented here but is fully described in the info documentation.
AUTHOR
? ? ? Written by David MacKenzie.
COPYRIGHT
? ? ? Copyright ? 2013 Free Software Foundation, Inc.? License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
? ? ? This is free software: you are free to change and redistribute it.? There is NO WARRANTY, to the extent permitted by law.
SEE ALSO
? ? ? The full documentation for date is maintained as a Texinfo manual.? If the info and date programs are properly installed at your site, the command
? ? ? ? ? ? ? info coreutils 'date invocation'
? ? ? should give you access to the complete manual.
三、實(shí)現(xiàn)晚上20:30自動(dòng)關(guān)機(jī)，并提示用戶
man shutdown?查閱shutdown的manual幫助得知
shutdown [OPTIONS...] [TIME] [WALL...]
因此得出 shutdown 20:30 'The system will be shutdown AT 20：30.'
后附查閱到的shutdown的manual幫助
NAME
? ? ? shutdown - Halt, power-off or reboot the machine
SYNOPSIS
? ? ? shutdown [OPTIONS...] [TIME] [WALL...]
DESCRIPTION
? ? ? shutdown may be used to halt, power-off or reboot the machine.
? ? ? The first argument may be a time string (which is usually "now"). Optionally, this may be followed by a wall message to be sent to all logged-in users before going down.
? ? ? The time string may either be in the format "hh:mm" for hour/minutes specifying the time to execute the shutdown at, specified in 24h clock format. Alternatively it may be in
? ? ? the syntax "+m" referring to the specified number of minutes m from now.? "now" is an alias for "+0", i.e. for triggering an immediate shutdown. If no time argument is
? ? ? specified, "+1" is implied.
? ? ? Note that to specify a wall message you must specify a time argument, too.
? ? ? If the time argument is used, 5 minutes before the system goes down the /run/nologin file is created to ensure that further logins shall not be allowed.
OPTIONS
? ? ? The following options are understood:
? ? ? --help
? ? ? ? ? Print a short help text and exit.
? ? ? -H, --halt
? ? ? ? ? Halt the machine.
? ? ? -P, --poweroff
? ? ? ? ? Power-off the machine (the default).
? ? ? -r, --reboot
? ? ? ? ? Reboot the machine.
? ? ? -h
? ? ? ? ? Equivalent to --poweroff, unless --halt is specified.
? ? ? -k
? ? ? ? ? Do not halt, power-off, reboot, just write wall message.
? ? ? --no-wall
? ? ? ? ? Do not send wall message before halt, power-off, reboot.
? ? ? -c
? ? ? ? ? Cancel a pending shutdown. This may be used cancel the effect of an invocation of shutdown with a time argument that is not "+0" or "now".
EXIT STATUS
? ? ? On success, 0 is returned, a non-zero failure code otherwise.
SEE ALSO
? ? ? systemd(1), systemctl(1), halt(8), wall(1)
四、總結(jié)歷史命令管理以及用法
????????登錄shell時(shí)，系統(tǒng)會(huì)讀取~/.bash_history中的歷史命令到緩存中。之后所有的命令操作都會(huì)先記錄在緩存中，只有在用戶正常退出的時(shí)候才會(huì)將緩存中新增的命令保存到~/.bash_history中。若用戶非正常退出則可能丟失緩存中的歷史命令。為避免此種情況發(fā)生，可以在系統(tǒng)操作中途可以輸入history -a追加本次會(huì)話新執(zhí)行的命令歷史列表至歷史文件。
? ? ? ? 若要完全清空歷史記錄不留痕跡，需要先刪除~/.bash_history里的內(nèi)容，再用history?-c清空緩存中未保存的歷史命令。
五、總結(jié)Linux幫助用法
? ? ? ? 會(huì)使用幫助，自己解決問(wèn)題特別重要。
? ? ? ? 在Linux中獲得幫助的途徑有一下這些：
? ??????????????whatis 命令。可以查看命令的man幫助出現(xiàn)在哪些章節(jié)，找到自己需要的章節(jié)。
? ? ? ? ? ? ? ? 命令 --help
? ? ? ? ? ? ? ? man 章節(jié) 命令
? ? ? ? ? ? ? ? info 命令
????????????????/usr/share/doc/
????????????????Red Hat documentation
????????????????其它網(wǎng)站和搜索
? ??????
