Linux Common commands

1. CD command

This is a very basic, is also a common need to use the command, it is used to switch the current directory, its parameters are to switch to the path of the directory, can be an absolute path, can also be a relative path. Such as:

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Cd/root/docements # Switch to directory/root/docements

cd./path # Switch to the path directory in the current directory, "." Represents the current directory

Cd.. /PATH # Switch to the path directory in the upper directory, "..." Represents a previous level of directory

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2. ls command

This is a very useful view of the file and directory commands, List of meaning, it has a lot of parameters, the following list some of my commonly used parameters, as follows:

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-L: Lists Long data strings, including file attributes and permission data, etc.

-A: Lists all the files, together with hidden files (files that begin with.) (common)

-D: Lists only the directory itself, not the file data for the directory

-H: List the file capacity in a more readable way (GB,KB, etc.)

-R: Listed along with the contents of the subdirectory (recursively listed), equal to all files in that directory will be displayed

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Note: These parameters can also be used in combination, the following two examples:

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Ls-l #以长数据串的形式列出当前目录下的数据文件和目录

LS-LR #以长数据串的形式列出当前目录下的所有文件

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3. grep command

This command is often used to parse a row of information, if there is information we need, the row is displayed, the command is usually used with the pipeline command, for the output of some commands to filter processing, etc., its simple syntax is

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grep [-ACINV] [--color=auto] ' Find string ' filename

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Its common parameters are as follows:

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-A: Find data in a binary file as a text file

-C: Calculate the number of times to find ' find string '

-I: Ignore case differences, that is, case is considered the same

-V: Reverse selection, which shows the line without the ' Find string ' content

For example

# Remove the line containing Manpath in the file/etc/man.config and add color to the Found keyword

grep--color=auto ' MANPATH '/etc/man.config

# put the output of ls-l with the letter file (case-insensitive) content output

Ls-l | Grep-i file

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4. Find command

Find is a very powerful search-based command, relatively speaking, its use is relatively complex, parameters are also more, so here will be to classify them, its basic syntax is as follows:

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Find [PATH] [option] [action]

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# time-related parameters:

-mtime N: = n is a number, meaning a file that has been changed in "One Day" before the nth day;

-mtime +n: Lists the file names that were changed before n days (excluding the N-day itself);

-mtime-n: Lists filenames that have been changed within n days (including n days themselves);

-newer file: List file names that are newer than file

For example

Find/root-mtime 0 # Find files that have changed within the current directory today

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# parameters related to user or user group name:

-user Name: List files with file owner name

-group Name: List files that belong to the user group named name

-uid N: List file owner as User ID n

-gid N: Lists files that belong to the user group whose user group ID is n

For example

Find/home/ljianhui-user Ljianhui # Find the owner-Ljianhui file in the directory/home/ljianhui

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# Parameters related to file permissions and names:

-name FileName: Find the file named filename

-size [+-]size: Find a file larger than size (+) or small (-)

-tpye Type: Find file of type of file, the value of type is mainly: General file (f), device file (b, C),

Directory (d), connection file (L), socket (s), FIFO pipeline file (p);

-perm mode: Find file permissions just equal to the mode file, mode is represented by a number, such as 0755;

-perm-mode: Find file permissions must all include the mode permission of the file, mode is represented by a number

-perm +mode: Find file Permissions file that contains the permissions of either mode, mode is represented by a number

For example

Find/-name passwd # Finding files with file name passwd

Find. -perm 0755 # 0755 file to find file permissions in the current directory

Find. -size +12k # Find files larger than 12KB in the current directory, note that C means byte

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5. CP command

This command is used to copy the file, copy the meaning, it can also copy multiple files to a directory at one time, its common parameters are as follows:

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-A: Copy the attributes of the file together

-P: Copied along with the properties of the file, not by default, similar to-a, often used for backup

-I: If the target file already exists, the action will be asked before overwriting

-R: Recursive continuous Replication for directory replication behavior

-U: The destination file is copied when it differs from the source file

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For example:

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Cp-a file1 file2 #连同文件的所有特性把文件file1复制成文件file2

CP file1 file2 file3 dir #把文件file1, file2, file3 copy to directory dir

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6. MV Command

This command is used to move a file, directory, or rename, and its common parameters are as follows:

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-f:force mandatory Meaning, if the target file already exists, will not ask and directly overwrite

-I: If the target file already exists, you will be asked to overwrite

-U: Updates if the target file already exists and is newer than the target file

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Note: This command can move a file or multiple files one folder at a time, but the last target file must be "directory".

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For example:

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MV File1 file2 file3 dir # move the file file1, File2, file3 to the directory dir

MV File1 file2 # Rename the file file1 to File2

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7. RM command

This command is used to delete files or directories, between remove, and its common parameters are as follows:

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-F: Force means ignoring files that do not exist and warning messages are not present

-I: Interactive mode, ask the user whether to operate before deleting

-R: Recursive delete, most commonly used for directory deletion, it is a very dangerous parameter

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For example:

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Rm-i File # To delete files, ask for the action before deleting

RM-FR dir # force removal of all files in directory dir

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8. PS command

This command is used to select and output the process run at a point in time, and its common parameters are as follows:

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-A: All processes are displayed

-A: All processes not related to terminal

-U: Related processes for effective users

-X: Generally used in conjunction with a parameter to list more complete information

-L: Longer, the PID information is listed in more detail

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In fact, we just need to remember the general use of PS command parameter collocation can be, they are not many, as follows:

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PS aux # View all process data for the system

PS Ax # View all processes not related to terminal

Ps-la # View all process data for the system

PS AXJF # View together with a subset of process tree states

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9. Kill command

This command is used to send a signal to a job (%jobnumber) or to a PID (number), which is typically used with the PS and jobs commands, with the following basic syntax:

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Kill-signal PID

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The common parameters of signal are as follows:

Note: The first number is the signal code, use can be used to replace the corresponding signal code.

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1:sighup, start the terminated process

2:sigint, equivalent to input CTRL + C, interrupts the process of a program

9:sigkill, forcing the interruption of a process

15:sigterm to terminate the process with normal end-of-process mode

17:sigstop, which is equivalent to input CTRL + Z, pauses a process

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For example:

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# at the end of the normal process to finally the first background work, you can use the Jobs command to view the background of the first worker process

Kill-sigterm%1

# re-change process ID to PID process, PID can be filtered using the PS command with the command of the command plus grep

Kill-sighup PID

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10. Killall command

This command is used to send a signal to a process initiated by a command whose general syntax is as follows:

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Killall [-iie] [command name]

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It has the following parameters:

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-I: interactive meaning, if need to delete, will ask the user

-E: Indicates that command name is followed by the same, but command name cannot exceed 15 characters

-I: Command name ignores case

For example

Killall-sighup syslogd # reboot SYSLOGD

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11. File command

This command is used to determine the basic data of files after the file command, because the type of the file under Linux is not the suffix of the future, so this command is very useful for us, its usage is very simple, the basic syntax is as follows:

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File filename

#例如:

File./test

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12. Tar command

This command is used to package the file, which is not compressed by default and, if specified, it also invokes the appropriate compression program (such as Gzip and bzip) for compression and decompression. Its common parameters are as follows:

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-C: New package file

-T: See what file names are included in the contents of the packaged files

-X: Unpacking or decompression function, can be used with-C (uppercase) to specify the extracted directory, note-c,-t,-x cannot appear in the same command

-J: Compression/decompression via BZIP2 support

-Z: Compression/decompression with GZIP support

-V: Displays the file name being processed during the compression/decompression process

-F filename:filename for files to be processed

-C dir: Specify a directory for compression/decompression dir

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The above commentary may have knocked you out of the way, but usually we just need to remember the following three commands:

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Compression: Tar-jcv-f filename.tar.bz2 The name of the file or directory to be processed

Enquiry: Tar-jtv-f filename.tar.bz2

Unzip: Tar-jxv-f filename.tar.bz2-c to extract the directory

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Note: The file name is not set to end in the suffix tar.bz2, this is mainly to illustrate the use of the compression program for BZIP2

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13. Cat Commands

This command is used to view the contents of a text file, followed by the name of the file to be viewed, and is typically used in conjunction with more and less to allow you to view the data one page at a time. For example:

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Cat text | Less # View the contents of the text file

# Note: This command can also use less text instead

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14. CHGRP command

This command is used to change the user group to which the file belongs, it is very simple to use, its basic usage is as follows:

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CHGRP [-R] Dirname/filename

-R: Recursive persistent changes to all files and subdirectories

For example

Chgrp users-r./dir # Recursively modifies the user group for all files and subdirectories under the Dir directory to users

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15. Chown Command

The command is used to change the owner of the file, using the same method as the CHGRP command, except that the modified file attributes are different and are no longer detailed.

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16. chmod command

This command is used to change the permissions of a file, as follows:

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chmod [-r] XYZ file or directory

-R: Continuous change of recursion, that is, all files under subdirectories are changed

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At the same time, chmod can also use the U (user), G (group), O (Other), a (all) and + (join),-(delete), = (set) with the rwx to make changes to the permissions of the file.

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For example

chmod 0755 File # Changes files permissions to-rxwr-xr-x

chmod g+w File # Adds a user group writable permission to files ' permissions

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18. Vim Command

This command is primarily used for text editing, which takes one or more file names as parameters, opens if the file exists, and creates a file with the file name if it does not exist. Vim is a very useful text editor, it has a lot of very useful commands, here no longer say. You can download a detailed description of VIM's common operations from here.

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19. GCC command

For a person who developed a C program with Linux, this command is very important, it is used to compile the C language source program files, compiled into an executable program, because many parameters of g++ and it very similar, so here only the parameters of the GCC, its common parameters are as follows:

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-o:output, used to specify the file name to generate an executable file

-C: Used to generate a target file (. o) from the source file and prevent the compiler from creating a complete program

-I: Increase the path of the search header file at compile time

-L: Increase the path of the search static connection library at compile time

-S: Generate assembly code files for source files

-LM: A library of libraries named LIBM.A in the directory that represents the standard library

-lpthread: Connecting NPTL-Implemented lines libraries

-std=: Used to specify the version of the C language to use

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For example

# Compile the source file test.c into executable program test according to C99 standard

Gcc-o Test Test.c-lm-std=c99

#把源文件test. c conversion to the appropriate assembler source file Test.s

Gcc-s test.c

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20. Time command

This command is used to measure the execution time of a command (that is, a program). It's very simple to use, just like you would normally enter a command, but add a time to the front of the command, for example:

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Time./process

Time PS aux

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After the program or command has finished running, it outputs three times at the end, respectively:

User: CPU time, the user CPU time that the command executes, that is, the command executes the sum of time in the user state;

System: CPU time, the system CPU time that the command executes, that is, the command executes the sum of time in the kernel mentality;

Real: The actual time, from the command line to start execution to the end of the elapsed time;

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Note: The sum of CPU time and system CPU time is CPU time, that is, the total amount of time the command consumes CPU execution. The actual time is greater than the CPU time, because Linux is a multitasking operating system, often when executing a command, the system also handles other tasks. Another problem to be aware of is that even though the same command is executed every time, the time spent is not the same, and the time spent is related to the operation of the system.

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21. Date

Date Displays the system date

Date 041217002007.00 sets the day and time of day-the year of the month. seconds

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22. Cal 2007 Displays the 2007 calendar table

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23. Clock-w Save time to BIOS

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24, Shutdown (System shutdown, restart and logout)

SHUTDOWN-H now shut down system (1)

Init 0 Shutdown System (2)

Telinit 0 Shutdown System (3)

Shutdown-h Hours:minutes & Shutdown system at scheduled times

Shutdown-c Cancel the system at a predetermined time

Shutdown-r now restart (1)

Reboot restart (2)

Logout logoff

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25, MkDir

mkdir dir1 Create a directory called ' Dir1 '

mkdir dir1 DIR2 Create two directories at a time

Mkdir-p/tmp/dir1/dir2 Create a directory tree

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26. Touch

Create a file

Linux Common commands