1.grep
grep supports basic regular expressions
egrep supports both basic and extended regular expressions
egrep = grep -E The
grep command is a Linux text processing tool that belongs to the same family as the egrep command, both of which are used to perform repetitions on files and text Tool for searching tasks. We can search files and their contents for useful information by specifying specific search criteria through grep command. grep is a global search for regular expressions and prints out the matching lines. Its fetching data is in a greedy mode, that is, the filtering content will not be missed, but the accuracy will be relatively reduced.
1.1 grep format
grep match conditions to process files
grep match condition processing file name
grep root passwd ##Filter the line where the root keyword is located
grep -i root passwd ##Ignore case and filter the line where the root keyword is located
grep -E "<root" passwd ##Filter the root character without before Lines of characters
grep -E "root>" passwd ##Filter lines without characters after the root character
grep -number ##Display filtered lines and the lines above and below
grep -n ##Display the line number where the matching line is located
grep -A number##displays the filtered line and the following lines
grep -B number##displays the filtered line and the upper lines
grep -v ##reverse filtering
experiment:
cp /etc/passwd .
ls
vim passwd
grep root passwd //搜索含有root关键字的行
grep -E "root|nologin" passwd
grep -e root -e nologin passwd //搜索含有root和nologin的行
grep -i root passwd //忽略大小写
grep -E "\<root" passwd //被搜索字符前不能有字符
grep -E "root\>" passwd //被搜索字符后不能有字符
grep -n halt passwd //显示搜索字符所在行的行号
grep -5 halt passwd //显示含有关键字的行和含有关键字行的上下各5行
grep -B5 halt passwd //显示含有关键字的行及上5行
grep -A5 halt passwd //显示含有关键字的行及下5行
grep root passwd -v //显示不含有root的行
1.2grep number of characters matching rules
| regular expression | meaning |
|---|---|
| ^ westos | starts with the westos keyword |
| westos $ | ends with westos |
| w…s | w starts with s and ends with 3 arbitrary characters |
| …s | 3 arbitrary characters before the end of s |
| * | Characters appear any number of times (ie 0 to any number of times) |
| ? | Character occurs 0 to 1 times |
| + | Character appears 1 to any number of times |
| {n} | character appears n times |
| {m,n} | Character appears m to n times |
| {,n} | character occurs 0 to n times |
| {m,} | Character appears at least m times |
| (lee){2} | lee string appears 2 times |
grep root passwd
grep ^root passwd //以root开头
grep root$ passwd //以root结尾
lab environment:
vim westos
cat westos
ws
was
wbs
waas
waaas
waaaas
wadads
wadadads
Experiment:
" . " represents any character
grep ws westos
grep w.s westos
grep w..s westos
grep w...s westos
2.sed
The full name of sed is stream editor, which is completely different from vim's interactive editing method. As a non-interactive editor, sed uses pre-set editing instructions to edit the input text, and output editing after completion. result. Its function is very powerful, with the support of regular expressions, it can edit a large number of complex texts.
Command format:
sed parameter command processing object
sed parameter processing object -f processing rule file
sed 's/nologin/westos/g' passwd
vim rule
cat rule
sed -f rule passwd
1.1 Handling of characters
p : show
sed 5p passwd //打印第五行
sed -n 5p passwd //只输出被处理内容
cat -b passwd | sed -n 3,5p //3-5行
cat -b passwd | sed -n '3p;5p' //3和5行
sed -n '/^root/p' passwd //root开头
sed -n '/bash$/p' passwd // bash结尾
sed -n '5,$p' passwd // 5到最后以行
sed -n '$p' passwd //最后一行
d: delete
cat -b passwd | sed '5d' 删除第5行
cat -b passwd | sed '5,8d' 5-8行
cat -b passwd | sed -e '5d;8d' 5和8行
sed -e '/^root/d' passwd root开头
sed -e '/bash$/d' passwd bash结尾
sed -e 'd' passwd 删除全部
a : add
sed '2aleo' westos 在第2行后添加
sed '/hello/aleo' westos 在hello的下面添加
sed '$aleo' westos 添加到最后一行
sed '$aleo\nwestoslinux' westos 最后添加两行 leo、westoslinux
c : replace
sed '1chhaha' westos 将第1行换成hhaha
sed '/linux/chaha' westos 将linux换成haha
w Write the matching line to the specified file
sed '/^UUID/w westofile' westos ##Write the line starting with UUID in westos into westosfile
i: insert
sed '/westos/iwestosfile' westos
r: integrate the file
sed '2rlee' westos
sed '/hello/rlee' westos
2.2 sed character replacement
sed 's/nologin/westos/g' passwd
sed '4,5s/nologin/westos/g' passwd
sed '$s/nologin/westos/g' passwd
sed '/lp/,/sssd/s/sbin/westos/g' passwd
sed 's/\//#####/g' passwd
sed 's@/@#####@g' passwd
sed 's@/@#####@g' -i passwd //将更改的内容保存到源文件
Replace nologin in the full text with westos Replace nologin in
lines 4 and 5 with westos
Replace nologin in the last line with westos
Replace sbin between lp and sssd with westos
Replace / with #####
Replace / with #####
3.awk
 character |
meaning |
|---|---|
| NO | Number of lines |
| NF | number of columns |
| FILENAME | the file name itself |
| westos | variable |
| Westos | string |
Set westos=1, each row westos+1 is processed, and the total value is finally output
awk -F : '/nologin$|{print $1,$7}' passwd
/bash$/ #条件
awk -F : '/nologin$|^root/{print $1,$7}' passwd
/条件1|条件2/ #条件1或者条件2
awk -F : '/nologin$/||/^root/{print $1,$7}' passwd
/条件1/||/条件2/ #条件1或者条件2
wk -F : '/bash$/&&/^root/{print $1,$7}' passwd
/条件1/&&/条件2/ #条件1并且条件2
$0#所有的列
$1#第一列
$2#第二列
$3#第三列
Show that the seventh column ends with bash.
After-school exercise: Command exercise: Count the number of users who can be switched by su in the system and whose home directory is not under /home
Ideas: Use the awk command to intercept /etc/passwd with: as the delimiter The sixth column in the file does not start with /home (/ needs to be translated; it cannot be directly written without the home keyword, there is a situation similar to the user's home directory being /tmp/home), and the line ending with bash or sh is correct. Intercept results to count
awk -F : 'BEGIN{N=0}$6!~/^\home/&&/bash$|sh$/{N++}END{print N}' /etc/passwd