20150827 after-school training assignments

First, homework (exercise) content:

1. Summarize the use of the commands involved in this course and show the relevant examples;

chmod

1. Order Explanation:

Change file permissions

Syntax structure:

chmod [OPTION] ... Mode[,mode] ... FILE ...

chmod [OPTION] ... Octal-mode FILE ...

chmod [OPTION] ...--reference=rfile FILE ...

Command options:
-r: The same permissions change for all files in the current directory and subdirectories (that is, they are changed in a recursive manner)

Three categories:

U:owner

G:group

O:other

A:all

Operation permissions for the specified category user:-

u-,g-,o-

Ug=,a=

To manipulate certain bit permissions for a certain type of user: +|-

u+,g+,o+

u-,g-,o-

Usage examples:

Modify 123.txt file A group has execute permissions:

chmod g+x/tmp/123.txt

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Modify the 123.txt file property to 777:

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650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpse339.tmp "border=" 0 "alt=" Wpse339.tmp "src=" Http://s3.51cto.com/wyfs02/M02/72/58/wKioL1XhgnHzJRJ5AAAPVp3oXiM332.jpg "height=" 6 "/>

Chown

1. Order Explanation:

Change the owner of a file

2. Command parameters:

chown [OPTION] ... [OWNER] [: [GROUP]] FILE ...

chown [OPTION] ...--reference=rfile FILE ...

3. Usage Examples:

Modify the owner of the/tmp/123.txt file, belonging to group Hzm Group of Hzm

Chown Hzm:hzm/tmp/123.txt

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650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpse34b.tmp "border=" 0 "alt=" Wpse34b.tmp "src=" Http://s3.51cto.com/wyfs02/M00/72/58/wKioL1XhgnGRpPepAAAO_SHEQOI639.jpg "height=" 6 "/>

Chgrp

1. Order interpretation;

Change the user group to which the file belongs

2. Command language

CHGRP [OPTION] ... GROUP FILE ...

CHGRP [OPTION] ...--reference=rfile FILE ...

3. Usage Examples:

Change the group of 123.txt files back to the root group:

CHGRP Root 123.txt

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650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;padding-left:0px; padding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpse34d.tmp "border=" 0 "alt=" Wpse34d.tmp "src=" Http://s3.51cto.com/wyfs02/M02/72/58/wKioL1XhgnLi8Po2AAAOUznVIT4559.jpg "height=" 6 "/>

Umask

Catalog: 777-umask

Files: 666-umask

If the permissions of a certain class of users have permission to execute, it will automatically add 1 to its permission bit.

Umask umask

Set: Valid only for the current shell process;

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2. Summarize basic regular expressions and extended regular expressions

Regular expression: Grep:global search REgular expression and Print out of the line.

Function: Text Search tool, according to user-specified "pattern" line to search for target text, print the matching line;

Pattern: The filter condition written by metacharacters and text characters of regular expressions;

Metacharacters: A character does not represent its literal meaning, but is used to denote a wildcard or control function;

Divided into two categories:

Basic Regular Expressions:

Character Matching:

. Match any single character

[] matches any single character within the specified range

[^] matches any single character outside the specified range

[0-9],[[:d igit:]],[^0-9],[^[:d igit:]]

[A-z],[[:lower:]]

[A-z],[[:upper:]]

[[: Space:]]

[[:p UNCT:]]

[0-9a-za-z],[[:alnum:]]

[A-za-z],[[:alpha:]]

Number of matches: A control is provided after the expected match character to express the number of times specified by the preceding character

* Any length, expressed 0 times, 1 or more times

. * Arbitrary length any character works in greedy mode

\？ Match its preceding characters 0 or 1 times, dispensable

\+ 1 or more times means that the preceding character must not be there, or multiple times

\{m\} its left character exactly matches M-Times

\{m,n\} at least m times, up to N times

\{m,\} at least M-Times is unlimited

Position Anchor Nails:

^ Anchor Beginning

$ Anchor Line End

^.. $ to match the entire line of content with a pattern

^$ Matching Blank lines

Word anchoring:

\< anchor Word first \b

\> anchor ending \b

\<parttern\> matches the entire word that Partern can match

Group: \ (\)

\ (\) \1 match pattern from left to right, matched by the first opening parenthesis and the pattern in the corresponding closing parenthesis

\ (\) \2 match pattern from left to right, with the second opening parenthesis and the pattern in the corresponding closing parenthesis

Note: Grouping patterns, the characters that are matched during the last specific match, can be memorized by grep (stored in the built-in variables, which are \1,\2 ...), and therefore can also be referenced

To extend the regular expression:

Character Matching:

. Any length, expressed 0 times, 1 or more times

. * Arbitrary length any character works in greedy mode

[] matches any single character within the specified range

[^] matches any single character outside the specified range

Number of matches:

* Any time

? Match its preceding characters 0 or 1 times, dispensable

+

{m}

{m,}

{0,n}

Position Anchor Nails:

^

$

\< \>, \b

Group:

() \1

Or

A|b|c A or B or C

Or anything on both sides.

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3. Display the lines in the/etc/passwd file that end with bash

Egrep bash$/etc/passwd

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4. Display the two-digit or three-digit number in the/etc/passwd file

Egrep--color=auto ' \<[0-9]{2,3}\> '/etc/passwd

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5. Displays the line with ' LISTEN ' followed by 0, one or more whitespace characters in the ' netstat-tan ' command result.

Netstat-tan | Egrep--color ' listen[[:space:]]+$ '

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6. Add user bash, Testbash, basher, and Nologin user (Nologin the user's shell is/sbin/nologin), and then find the line in the/etc/passwd file that has the same user name as its shell name.

Egrep "\< ([[:alnum:]]+\>). *\1$"/etc/passwd | Cut-d:-F 1,7

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7. Display the default shell and UID of root, CentOS, or User1 user on the current system (please create these users beforehand, if not present)

Egrep "\<root|centos|user1\>"/etc/passwd | Cut-d:-F 3,7

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpse363.tmp "border=" 0 "alt=" Wpse363.tmp "src=" http://s3.51cto.com/wyfs02/M00/72/58/wKioL1XhgnPRbdHkAABvj37x0nI236.jpg "height="/>

8, find a word in the/etc/rc.d/init.d/functions file (the middle of the word can be underlined) followed by a set of parentheses line

Egrep--color=auto ' \<[[:alnum:]]+\>\ (\) '/etc/rc.d/init.d/functions

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9, use echo to output a path, and then egrep find its path base name; Further use Egrep to remove its directory name

echo/etc/passwd/| Egrep-o "[[: alnum:]]+\/?$]--color

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echo/etc/init.d/iptables/| Egrep-o "^\/.*\/"

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10. Find the number between 1-255 in the result of ifconfig command execution

Ifconfig | Egrep ' \< ([1-9]|[ 1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5]) \> '--color

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20150827 after-school training assignments