阿菜ing

# dd if=/dev/zero of=/swap2gb bs=1024k count=2000
# mkswap /swap2gb                    # 创建交换区
# swapon /swap2gb                    # 激活这个 swap。现在可以使用了
# swapoff /swap2gb                   # 当使用完毕,释放这个 swap
# rm /swap2gb

jcai@jcai-notebook:~/tmp$ cat ps3.sh 
  select i in mon tue wed exit
  do
     case $i in
        mon) echo "Monday";;
        tue) echo "Tuesday";;
        wed) echo "Wednesday";;
        exit) exit;;
     esac
  done
jcai@jcai-notebook:~/tmp$ ./ps3.sh 
1) mon
2) tue
3) wed
4) exit
#? 1
Monday
#? 2
Tuesday
#? 4

jcai@jcai-notebook:~/tmp$ cat ps3.sh
  PS3="请选择 1-4："
  select i in mon tue wed exit
  do
     case $i in
        mon) echo "Monday";;
        tue) echo "Tuesday";;
        wed) echo "Wednesday";;
        exit) exit;;
     esac
  done
jcai@jcai-notebook:~/tmp$ ./ps3.sh 
1) mon
2) tue
3) wed
4) exit
请选择 1-4：2
Tuesday
请选择 1-4：4

# mount | column -t        # 显示系统已挂载分区情况
# df                       # 显示磁盘剩余空间和挂载的设备
# cat /proc/partitions     # 显示所有设备的所有分区(Linux)

   $ ac –d
   Dec 1      total             1.08
   Dec 2      total             0.99
   Dec 3      total             3.39
   Dec 4      total             4.50
   Today      total             6.10

   $ ac -p
              john                                            3.64
              madison                                      0.06
              sanjay                                          88.17
              nisha                                           105.92
             ramesh                                        111.42
             total 309.21

  $ ac -d sanjay
  Jul 2      total          12.85
  Aug 25     total            5.05
  Sep 3      total            1.03
  Sep 4      total            5.37
  Dec 24     total            8.15
  Dec 29     total            1.42
  Today      total            2.95

 # unload
 # load kernel.old
 # boot

   Syntax: diff [options] file1 file2

jcai@jcai-notebook:~$ diff --help
Usage: diff [OPTION]... FILES
Compare files line by line.
 
  -i  --ignore-case  Ignore case differences in file contents.
  --ignore-file-name-case  Ignore case when comparing file names.
  --no-ignore-file-name-case  Consider case when comparing file names.
  -E  --ignore-tab-expansion  Ignore changes due to tab expansion.
  -b  --ignore-space-change  Ignore changes in the amount of white space.
  -w  --ignore-all-space  Ignore all white space.
  -B  --ignore-blank-lines  Ignore changes whose lines are all blank.
  -I RE  --ignore-matching-lines=RE  Ignore changes whose lines all match RE.
  --strip-trailing-cr  Strip trailing carriage return on input.
  -a  --text  Treat all files as text.
 
  -c  -C NUM  --context[=NUM]  Output NUM (default 3) lines of copied context.
  -u  -U NUM  --unified[=NUM]  Output NUM (default 3) lines of unified context.
    --label LABEL  Use LABEL instead of file name.
    -p  --show-c-function  Show which C function each change is in.
    -F RE  --show-function-line=RE  Show the most recent line matching RE.
  -q  --brief  Output only whether files differ.
  -e  --ed  Output an ed script.
  --normal  Output a normal diff.
  -n  --rcs  Output an RCS format diff.
  -y  --side-by-side  Output in two columns.
    -W NUM  --width=NUM  Output at most NUM (default 130) print columns.
    --left-column  Output only the left column of common lines.
    --suppress-common-lines  Do not output common lines.
  -D NAME  --ifdef=NAME  Output merged file to show `#ifdef NAME' diffs.
  --GTYPE-group-format=GFMT  Similar, but format GTYPE input groups with GFMT.
  --line-format=LFMT  Similar, but format all input lines with LFMT.
  --LTYPE-line-format=LFMT  Similar, but format LTYPE input lines with LFMT.
    LTYPE is `old', `new', or `unchanged'.  GTYPE is LTYPE or `changed'.
    GFMT may contain:
      %<  lines from FILE1
      %>  lines from FILE2
      %=  lines common to FILE1 and FILE2
      %[-][WIDTH][.[PREC]]{doxX}LETTER  printf-style spec for LETTER
        LETTERs are as follows for new group, lower case for old group:
          F  first line number
          L  last line number
          N  number of lines = L-F+1
          E  F-1
          M  L+1
    LFMT may contain:
      %L  contents of line
      %l  contents of line, excluding any trailing newline
      %[-][WIDTH][.[PREC]]{doxX}n  printf-style spec for input line number
    Either GFMT or LFMT may contain:
      %%  %
      %c'C'  the single character C
      %c'\OOO'  the character with octal code OOO
 
  -l  --paginate  Pass the output through `pr' to paginate it.
  -t  --expand-tabs  Expand tabs to spaces in output.
  -T  --initial-tab  Make tabs line up by prepending a tab.
 
  -r  --recursive  Recursively compare any subdirectories found.
  -N  --new-file  Treat absent files as empty.
  --unidirectional-new-file  Treat absent first files as empty.
  -s  --report-identical-files  Report when two files are the same.
  -x PAT  --exclude=PAT  Exclude files that match PAT.
  -X FILE  --exclude-from=FILE  Exclude files that match any pattern in FILE.
  -S FILE  --starting-file=FILE  Start with FILE when comparing directories.
  --from-file=FILE1  Compare FILE1 to all operands.  FILE1 can be a directory.
  --to-file=FILE2  Compare all operands to FILE2.  FILE2 can be a directory.
 
  --horizon-lines=NUM  Keep NUM lines of the common prefix and suffix.
  -d  --minimal  Try hard to find a smaller set of changes.
  --speed-large-files  Assume large files and many scattered small changes.
 
  -v  --version  Output version info.
  --help  Output this help.
 
FILES are `FILE1 FILE2' or `DIR1 DIR2' or `DIR FILE...' or `FILE... DIR'.
If --from-file or --to-file is given, there are no restrictions on FILES.
If a FILE is `-', read standard input.

jcai@jcai-notebook:~/tmp$ cat test.txt
我们
你们现在还好吗？比较文本
jcai@jcai-notebook:~/tmp$ cat test2.txt
他们
我们
你们现在还好吗？
jcai@jcai-notebook:~/tmp$ diff test.txt test2.txt
0a1
> 他们
2c3
< 你们现在还好吗？比较文本
---
> 你们现在还好吗？

# diskinfo -v /dev/ad2 # 显示磁盘信息(扇区/大小) (FreeBSD)
# hdparm -I /dev/sda   # 显示 IDE/ATA 磁盘信息 (Linux)
# fdisk /dev/ad2       # 显示和修改磁盘分区表
# smartctl -a /dev/ad2 # 显示磁盘检测信息