unswit / comp9044-19t2

Software Construction

COMP9044-19T2

Software Construction

LAB 01

Shell 正则表达式(BRE)

• ? 表示前面的字符可以出现0次或1次,匹配成立

• | 表示 or

• + 表示前面的字符可以出现1次或者多次,但必须出现至少1次

  • '([0-9]+,)*'

    • 2,4,8,16,32

• u* 表示字母u可能出现或者不出现的匹配模式的文本中

• 且如果出现前有多个字符的情况AB*只表示B可能出现或者不出现

(在字符后面放置星号标明该字符必须在匹配模式的版本中出现0次或者多次)

cat

• -n number output lines (starting from 1) 输出多少行
• -s squeeze consecutive blank lines into single blank line 将连续的空白行压缩成一行空白行
• -v display control-characters in visiable form

wc

• -c counts the number of characters (include "." )
• -w count the number of words(non-white space)
• -l count the number of lines

tr

tr ’sourceChars’ ’destChars’ < dataFile

将dataFile 里面的’sourceChars’替换成’destChars’

• -c map all characters not occurring in sourceChars
• -s squeeze adjacent repeated characters out(only copy the first)
• -d delete all characters in sourceChars
  • Example
    • tr -cs ’a-zA-Z0-9’ ’\n’ < text (break text file into individual words, one per line)

head/tail

• -n 前/后n行

egrep

• -i ignore upper/lower-case difference in matching
• -v only display lines that do not match the pattern
• -w only match pattern if it makes a complete word

egrep其实就是grep的扩展版

• grep -P Perl-like extended regular expressions

  • Lab01 question中有一道题利用此条命令

    • grep -P '^(A(?1)?B)$' input.txt (AABB)

cut

• -f print only the specificed filed
• -c print only chars in the specificed filed
• -d'c' use character c as the filed separator
  • cut -f4- 两个杠表示 print all colums after the third

sort

• -r sort in descending order (reverse sort) sort

• -n numerically rather than lexicographically dictionary

• -dorder: ignore non-letters and non-digits use character

• -t’c’ c to separate columns (default: space)

• -kn’sort on column n

uniq

• -c print number of times each line is duplicated
• -d only print duplicated line
• -u only print lines that occur uniquely(once only)

xargs

• remove home directories of users named Andrew:

  -grep Andrew /etc/passwd | cut -d: -f6 | xargs rm -r - 1. 通过grep /etc/passwd 中的关键字 - 2. 在通过cut来获取关键字后的路径 - 3. 删除路径中的文件

join

• join -a 1 P.txt Q.txt
  • Print non pairable lines from first file.
    • 打印出不同的

matcher

1. tr -d '[]"#'
   • delete []"# in the string