7.4facl及while和until循環

NAME
       sleep - delay for a specified amount of time  延遲指定的秒數

SYNOPSIS
       sleep NUMBER[SUFFIX]...
       sleep OPTION

DESCRIPTION
       Pause  for  NUMBER  seconds.   SUFFIX  may be ‘s’ for seconds (the
       default), ‘m’ for minutes, ‘h’ for hours or ‘d’ for days.
crontab任務在關機狀態下任務是不執行的，且開機後不在時間點上也是不執行的

        anacron: crontab的補充機制
            檢查有沒有過去一個有效週期不曾執行的任務，若是有，在開機後的指定時間點執行一次；

    總結：
        任務計劃：
            一次性：at, batch
            週期性：cron

        cron:
            PATH環境變量
            任務時間格式       
           

facl: file acl
    acl: access control list

    chown: 普通用戶可否改變文件的屬主屬組？  不行
    chmod: 普通用戶是否有權限使用？  有

    openstack用戶，docker（讀寫）

    經過facl機制，普通用戶能夠單獨向某用戶或某組設定對某文件訪問權限；不經過修改屬主或屬組來實現的。

    文件系統：
        ext: extended
            ext2, ext3, ext4,
            xfs（單個文件無邊界）

NAME
       lsattr - list file attributes on a Linux second extended file system
         列出文件系統擴展的屬性主要對 ext的擴展
SYNOPSIS
       lsattr [ -RVadv ] [ files...  ]

DESCRIPTION
       lsattr lists the file attributes on a second extended file system.
       See  chattr(1)  for  a description of the attributes and what they
       mean.
[root@root ~]#lsattr test
-------------e- test   有e顯示錶示支持擴展格式
NAME
       chattr - change file attributes on a Linux file system
         改變Linux文件系統屬性
SYNOPSIS
       chattr [ -RVf ] [ -v version ] [ mode ] files...

DESCRIPTION
       chattr changes the file attributes on a Linux file system.

       The format of a symbolic mode is +-=[acdeijstuADST].
             這個格式向這種模式
       The operator ‘+’ causes the selected attributes to be added to the
       existing attributes of the files; ‘-’ causes them to  be  removed;
       and ‘=’ causes them to be the only attributes that the files have.   
       a：只能往裏面追加內容  c:壓縮的格式  d：標記爲還沒有備份
       e:擴展格式  i：不能變  j:設置數據日誌 s:安全刪除
       t:不在尾部執行合併 u：不可刪除 A：不更新訪問時間戳 D：同步目錄更新
       S:同步更新，文件更新  T:把目錄設置爲等級目錄結構
       The letters ‘acdeijstuADST’ select  the  new  attributes  for  the
       files: append only (a), compressed (c), no dump (d), extent format
       (e), immutable (i), data journalling (j), secure deletion (s),  no
       tail-merging  (t),  undeletable  (u),  no  atime updates (A), syn-
       chronous directory updates (D), synchronous updates (S),  and  top
       of directory hierarchy (T).

       The  following  attributes  are  read-only,  and  may be listed by
       lsattr(1) but not modified by chattr: huge file  (h),  compression
       error  (E), indexed directory (I), compression raw access (X), and
       compressed dirty file (Z).
        
        lsattr, chattr
            i  不能改變文件內容
            u  不能刪除文件
            A 不更新訪問時間戳

    facl:
        讓普通用戶透過文件的擴展屬性，爲其添加額外的用戶訪問受權機制而無須改
        變其屬主、屬組，也不用更改other的權限；

        getfacl
        NAME
       getfacl - get file access control lists
          獲得文件的訪問控制列表
        [root@root ~]#getfacl test
        # file: test
        # owner: root
        # group: root
        user::rw-
        group::r--
        other::r--

        setfacl {-m|-x} 目標:MODE FILE...
        NAME
       setfacl - set file access control lists
                設置文件訪問控制列表
        SYNOPSIS
               setfacl  [-bkndRLPvh]  [{-m|-x}  acl_spec] [{-M|-X} acl_file] file
               ...
       
               setfacl --restore=file
       
        DESCRIPTION
               This utility sets Access Control Lists (ACLs) of files and  direc-
               tories.   On  the command line, a sequence of commands is followed
               by a sequence of files (which in turn can be followed  by  another
               sequence of commands, ...).
        The -m (--modify) and -M (--modify-file) options modify the ACL of
       a  file or directory.  ACL entries for this operation must include
       permissions. 修改屬性

   The -x  (--remove)  and  -X  (--remove-file)  options  remove  ACL
   entries.  It  is  not  an  error to remove an entry which does not
   exist.  Only ACL entries without the perms field are  accepted  as
   parameters, unless POSIXLY_CORRECT is defined. 移除屬性
            -m u:USERNAME:MODE
            -m g:GROUPNAME:MODE

            -x u:USERNAME
            -x g:GROUPNAME

            -R: 遞歸
[openstack@root ~]$getfacl hello
# file: hello
# owner: openstack
# group: openstack
user::r--
group::rw-
other::rw-

[openstack@root ~]$ls -l
total 0
-r--rw-rw-. 1 openstack openstack 0 Dec 29 20:34 hello
[openstack@root ~]$chmod o= hello
[openstack@root ~]$ls hello -l
-r--rw----. 1 openstack openstack 0 Dec 29 20:34 hello
[openstack@root ~]$setfacl -m u:freebsd:rw hello
[openstack@root ~]$getfacl hello
# file: hello
# owner: openstack
# group: openstack
user::r--
user:freebsd:rw-
group::rw-
mask::rw-
other::---
[openstack@root ~]$ls -l
total 4
-r--rw----+ 1 openstack openstack 0 Dec 29 20:34 hello  . -> +號了
[openstack@root ~]$setfacl -x u:freebsd hello
[openstack@root ~]$getfacl hello
# file: hello
# owner: openstack
# group: openstack
user::r--
group::rw-
mask::rw-
other::---
訪問文件的過程：先檢查進程運行者用戶是否是文件的屬主，若是是，屬主權限生效，不然，則檢查
有沒有跟此用戶相關的用戶訪問控制列表，若是有，用戶訪問控制列表生效，不然，則檢查進程的屬組
所屬的組其中之一是否是和文件屬組有一個相同，若是有應用屬組權限，不然，檢查訪問控制列表中的
屬組，若是有，應用訪問控制列表，不然其餘用戶來訪問
屬主的訪問權限是高於基於用戶的訪問控制列表，屬組的訪問權限也是高於基於屬組的訪問控制列表

        啓用facl以後權限應用模型：
            屬主： 匹配則應用
            用戶級別的facl:  匹配則應用
            屬組：匹配則應用 
            組級別的facl:
            其它

bash編程之循環：
    順序
    選擇：if
    循環：for

    另外一種循環：while 和 until
        for i in {1..100}; do

        done

        while適用於循環次數未知，或不便用for直接生成較大的列表時；

        while 測試條件; do
            循環體
        done

        如測試結果爲「真」，則進入循環；退出條件爲，測試條件爲假；

            declare -i count=1
            while $count <= 1000; do
                循環體
                let count++
            done

        until 測試條件; do
            循環體
        done

        若是測試結果爲「假」，則進入循環；退出條件爲，測試條件爲真；

        練習：求100之內全部正整數之和

            #!/bin/bash
            #
            declare -i count=1
            declare -i sum=0

            until [ $count -gt 100 ]; do
                let sum+=$count
                let count++
            done

            echo $sum

            #!/bin/bash
            #
            declare -i count=1
            declare -i sum=0

            while [ $count -le 100 ]; do
                let sum+=$count
                let count++
            done

            echo $sum

        練習：求100之內全部偶數之和；要求使用取模方法；

            #!/bin/bash
            #
            declare -i counter=1
            declare -i sum=0

            while [ $counter -le 100 ]; do
                if [ $[$counter%2] -eq 0 ]; then
                    let sum+=$counter
                fi
                let counter++
            done

            echo $sum

            #!/bin/bash
            #
            declare -i counter=1
            declare -i sum=0

            while [ $counter -le 100 ]; do
                [ $[$counter%2] -eq 0 ] && let sum+=$counter
                let counter++
            done

            echo $sum

            請用until實現上述過程；
            [root@root scripts]#./evensum.sh
            The sum is 2550.
            The sum1 is 2500.
            The sum add sum1 is 5050.
            [root@root scripts]#cat evensum.sh
            #!/bin/bash
            #
            declare -i num=1
            declare -i sum=0
            declare -i sum1=0
           
            until [ $num -gt 100 ]
            do
            #     sum=$[$sum+$num]
            #     let num++
                [ $[$num%2] -eq 0 ] && sum=$[$sum+$num] || sum1=$[$sum1+$num]
                let num++
            done
           
            echo "The sum is $sum."
            echo "The sum1 is $sum1."
            echo "The sum add sum1 is $[$sum+$sum1]."

        練習：提示用戶輸入一個用戶名，若是用戶存在，就顯示用戶的ID號和shell；不然顯示用戶不存在；
              顯示完成以後不退出，再次重複前面的操做，直到用戶輸入q或quit爲止；

              read -p "Plz enter a username: " userName

              while [ "$userName" != 'q' -a "$userName" != 'quit' ]; do
                    if id $userName &> /dev/null; then
                        grep "^$userName\>" /etc/passwd | cut -d: -f3,7
                    else
                          echo "No such user."
                    fi

                    read -p "Plz enter a username again: " userName
              done

            請用until實現上述過程；

read -p "Plz input user name:" username

until [ "$username" == "q" -o "$username" == "quit" ];do       if ! id "$username" &> /dev/null;then          echo "$username not exists."       else          grep "$username" /etc/passwd |cut -d: -f1,7       fi             read -p "Plz input user name:" username done