第 2 堂課：指令下達行為與基礎檔案管理

[student@localhost ~]$ command  [-options]  [parameter1...]

[student@localhost ~]$ date
四  4月 21 02:43:24 CST 2016

[student@localhost ~]$ date +%Y/%m/%d
2016/04/21

[student@localhost ~]$ date --help
Usage: 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=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     顯示此求助說明並離開
      --version  顯示版本資訊並離開

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)
........

[student@localhost ~]$ date --help
Usage: 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.

[student@localhost ~]$ date 042211072016
date: cannot set date: Operation not permitted
Fri Apr 22 11:07:00 CST 2016
[student@localhost ~]$ date
Fri Apr 22 19:05:17 CST 2016

[student@localhost ~]$ su -
密碼：
上一次登入：四  4月 21 02:42:42 CST 2016在 tty2
[root@localhost ~]# 

[root@localhost ~]# date 042211142016
Fri Apr 22 11:14:00 CST 2016
[root@localhost ~]# date
Fri Apr 22 11:14:02 CST 2016

[student@localhost ~]$ date
五  4月 22 11:24:09 CST 2016
[student@localhost ~]$ LANG=en_US.utf8
[student@localhost ~]$ date
Fri Apr 22 11:24:46 CST 2016

[student@localhost ~]$ echo ${LANG}
en_US.utf8

[student@localhost ~]$ bc
bc 1.06.95
Copyright 1991-1994, 1997, 1998, 2000, 2004, 2006 Free Software Foundation, Inc.
This is free software with ABSOLUTELY NO WARRANTY.
For details type `warranty'.
1+2+3+4
10
1/3
0
quit

[student@localhost ~]$ man bc
bc(1)                      General Commands Manual                      bc(1)

NAME
       bc - An arbitrary precision calculator language

SYNTAX
       bc [ -hlwsqv ] [long-options] [  file ... ]

DESCRIPTION
       bc is a language that supports arbitrary precision numbers with inter‐
       active execution of statements.  There are some  similarities  in  the
       syntax  to  the  C  programming  language.  A standard math library is
       available by command line option.  If requested, the math  library  is
       defined  before  processing  any  files.  bc starts by processing code
       from all the files listed on the command line  in  the  order  listed.
       After all files have been processed, bc reads from the standard input.
       All code is executed as it is read.  (If a file contains a command  to
       halt the processor, bc will never read from the standard input.)
.......

   OPTIONS
       -h, --help
              Print the usage and exit.

       -i, --interactive
              Force interactive mode.
.......

   VARIABLES
       There  are  four  special  variables,  scale,  ibase, obase, and last.
       scale defines how some operations use digits after the decimal  point.
       The default value of scale is 0. ibase and obase define the conversion
       base for input and output numbers.  The default  for  both  input  and
       output  is  base  10.   last (an extension) is a variable that has the
       value of the last printed number.  These will be discussed in  further
       detail  where  appropriate.   All  of  these variables may have values
       assigned to them as well as used in expressions.
.......

       - expr The result is the negation of the expression.

       ++ var The  variable  is  incremented  by one and the new value is the
              result of the expression.

       -- var The variable is decremented by one and the  new  value  is  the
              result of the expression.

       var ++
               The  result of the expression is the value of the variable and
              then the variable is incremented by one.

       var -- The result of the expression is the value of the  variable  and
              then the variable is decremented by one.

       expr + expr
              The result of the expression is the sum of the two expressions.
.......

AUTHOR
       Philip A. Nelson
       philnelson@acm.org

ACKNOWLEDGEMENTS
       The author would like to thank Steve  Sommars  (Steve.Sommars@att.com)
       for his extensive help in testing the implementation.  Many great sug‐
       gestions were given.  This  is  a  much  better  product  due  to  his
       involvement.

GNU Project                       2006-06-11                            bc(1)

[student@localhost ~]$ echo "scale=10; 4*a(1)" | bc -l

[student@localhost ~]$ ll /etc/ | grep 'passwd'

[student@localhost ~]$ df
檔案系統                 1K-區段    已用    可用 已用% 掛載點
/dev/mapper/centos-root 10475520 4024880 6450640   39% /
devtmpfs                 1008980       0 1008980    0% /dev
tmpfs                    1024480      96 1024384    1% /dev/shm
tmpfs                    1024480    8988 1015492    1% /run
tmpfs                    1024480       0 1024480    0% /sys/fs/cgroup
/dev/vda2                2086912  150216 1936696    8% /boot
/dev/mapper/centos-home  3135488   41368 3094120    2% /home
tmpfs                     204900      20  204880    1% /run/user/1000

[student@localhost ~]$ ls
下載  公共  圖片  影片  文件  桌面  模板  音樂
[student@localhost ~]$ cd /var/spool/mail
[student@localhost mail]$ ls
root  rpc  student 

[student@localhost mail]$ pwd
/var/spool/mail
[student@localhost mail]$ 

[student@localhost mail]$ cd /etc
[student@localhost etc]$ pwd
/etc
[student@localhost etc]$ cd /usr/local/etc
[student@localhost etc]$ pwd
/usr/local/etc
[student@localhost etc]$