Basic knowledge of Linux Learning (v)

1. Display the default shell of root, fedora or User1 user on the current system;

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Note: Egrep ' ^ (ROOT|FEDORA|USR1) \> '/etc/passwd to find/etc/passwd users from Root,fedora,user1, exists on the match, does not exist on the skip;

Cut-d:-f1,7 Intercept First and seventh fields

2. Find the line with a set of parentheses after a word in the/etc/rc.d/init.d/functions file, such as: Hello ();

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Note: Refer to the blog post of Cix123 classmate, feel very detailed, so also write down:

^[_[:alpha:]]+ _: Indicates the beginning of an _ or uppercase letter,

+: Indicates that the preceding character can appear one or more times,

\ (\): Can actually be split into \ (and \), using the \ escape character;

3. Use the echo command to output an absolute path, using grep to remove its base name;

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Note: If there is no "/" after Echo "/tmp/log", use Grep-e-O "[^/]+$]

If echo "/tmp/log/" is followed by "/", then use GREP-E-O "[^/]+/?$",/? Indicates that it can occur 1 times or does not appear

Extension: Take out its path name

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4, find out the results of the ifconfig command between 1-255 numbers;

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5, Challenge: Write a mode, can match the reasonable IP address;

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6, Challenge: Write a pattern, can match out all the email address;

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7. Find the main root of the/var directory, and belong to all files or directories of mail;

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Note: Currently in use of the system does not match, so changed a group GDM, but the effect is the same, this can be flexibly handled

8, find the current system does not belong to the main or group of files;

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Further: Find files or directories that are not owned by the master or group on the current system and have been visited in the last 3 days;

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Note:-mtime-n +n The file changes time to find the file,-n means that the file change time is now less than n days, + n means that the file change time is now N days ago.

9, find all the users in/etc directory have write permission files;

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10. Find all files that are larger than 1M in/etc directory and are of normal file type;

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Note:-size + file size-type file type

11, find/etc/init.d/directory, all users have execute permission, and other users have write permission files;

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12. Find files that do not belong to root, bin or hadoop in the/usr directory;

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Note: Hadoop users do not have, business system, do not tamper with it, and the next add a more because the matching file too much turned, too lazy to page;

Simpler way: Find/usr-not \ (-user root-o-user bin-o-user hadoop \)

Here's a pit. I hint: "\ (" and "-user" must be separated by a space, otherwise it will report the following error, then I did not understand, depressed for a long time to find. 650) this.width=650; "src=" Http://s2.51cto.com/wyfs02/M00/86/D6/wKioL1fM4R_j2ZEIAAAh3cOeU54385.png "title=" 16.png "alt=" Wkiol1fm4r_j2zeiaaah3coeu54385.png "/>

13, to find at least one type of/etc/directory Users do not have write permission files;

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14. Find files whose contents have been modified and not rooted or Hadoop for the last week in/etc directory;

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Note: find/etc/-mtime-7 is to find files that have been modified in the last week;-not-user Root-not-user-hadoop is to find files that are not root or Hadoop

Small description of the-A and-O parameters:-a:and, if condition 1 is false then condition 2 is not performed,-o:or if the condition 1 bit true condition 2 is not executed.

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Basic knowledge of Linux Learning (v)