Files and directories
- cd command is used to switch the current directory. Its parameter is the path of the directory to be switched to, which can be absolute path or relative path.
cd /home get into '/ home' catalogue cd .. Return to the previous directory cd ../.. Return to the upper two directories cd Enter personal home directory cd ~user1 Enter personal home directory cd - Return to the last directory
- pwd command, displaying the working path
[root@mailvip ~]# pwd /root
- ls command, the command to view files and directories, which means list
ls View files in directory ls -l Displays details of files and directories ls -a Lists all files, including hidden files ls -R List together with the contents of the subdirectory (recursive list), which means that all files in the directory will be displayed ls [0-9] Displays the file and directory names that contain numbers
4.cp command is used to copy files, which means copy. It can also copy multiple files to a directory at one time
-a : Copy the properties of the file together -p : Copy along with the properties of the file instead of using the default method, and-a Similar, often used for backup -i : If the target file already exists, the operation will be queried first when overwriting -r : Recursive continuous replication is used for directory replication behavior //Recursive replication is often used -u : The target file is copied only when there is a difference between the target file and the source file
- mv command, used to move files, directories or rename, which means move
-f : force Mandatory means that if the target file already exists, it will not be queried but directly overwritten -i : If the target file already exists, you will be asked whether to overwrite it -u : If the target file already exists and is newer than the target file, it will be updated
- rm command, used to delete files or directories, which means remove
-f : namely force Ignore nonexistent files and no warning message will appear -i : Interactive mode, the user will be asked whether to operate before deletion -r : Recursive deletion is most commonly used for directory deletion. It is a very dangerous parameter
view file contents
- cat command is used to view the contents of a text file followed by the file name to be viewed. It can usually be used with more and less through a pipeline
cat file1 View the contents of the file forward from the first byte tac file1 View the contents of a file in reverse from the last line cat -n file1 Indicates the number of lines in the file more file1 View the contents of a long file head -n 2 file1 View the first two lines of a file tail -n 2 file1 View the last two lines of a file tail -n +1000 file1 Display from 1000 lines, and display the data after 1000 lines cat filename | head -n 3000 | tail -n +1000 Display 1000 to 3000 lines cat filename | tail -n +3000 | head -n 1000 Starting at line 3000, 1000 is displayed(3000 is displayed~3999 that 's ok)
File search
- The find command is used to find the name of the system
find / -name file1 from '/' Start searching the root file system for files and directories find / -user user1 Search for users 'user1' Files and directories for find /usr/bin -type f -atime +100 Search for executables that have not been used in the past 100 days find /usr/bin -type f -mtime -10 Search for files created or modified within 10 days whereis halt Displays a binary file, source code, or man Location of which halt Displays the full path of a binary or executable file
Delete files larger than 50M:
find /var/mail/ -size +50M -exec rm {} ＼;
File permissions - use "+" to set permissions, and "-" to cancel permissions
- chmod command to change file / folder permissions
ls -lh Display permissions chmod ugo+rwx directory1 Set the owner of the directory(u),group (g)And others(o)To read( r，4 ),write(w，2)And Implementation(x，1)Permissions for chmod go-rwx directory1 Delete Group (g)With others(o)Read / write execute permissions on the directory
- chown command to change the owner of the file
chown user1 file1 Change the owner attribute of a file chown -R user1 directory1 Change the owner attribute of a directory and change the attributes of all files in the directory at the same time chown user1:group1 file1 Change the owner and group properties of a file
- chgrp command to change the user group to which the file belongs
chgrp group1 file1 Change the group of files
text processing
- grep command analyzes a line of information. If there is any information we need, it will be displayed. This command is usually used together with pipeline command to filter and process the output of some commands, etc
grep Aug /var/log/messages In file '/var/log/messages'Find keywords in"Aug" grep ^Aug /var/log/messages In file '/var/log/messages'Find in to"Aug"Starting vocabulary grep [0-9] /var/log/messages choice '/var/log/messages' All lines in the file that contain numbers grep Aug -R /var/log/* In directory '/var/log' And subsequent directories"Aug" sed 's/stringa1/stringa2/g' example.txt take example.txt In file "string1" replace with "string2" sed '/^$/d' example.txt from example.txt Delete all blank lines from the file
- paste command
paste file1 file2 Merge the contents of two files or two columns paste -d '+' file1 file2 Merge the contents of two files or two columns, with"+"distinguish
- sort command
sort file1 file2 Sort the contents of two files sort file1 file2 | uniq Take out the union of two files(Keep only one copy of duplicate lines) sort file1 file2 | uniq -u Delete the intersection and leave other rows sort file1 file2 | uniq -d Take out the intersection of two files(Only files that exist in both files are left)
- comm command
comm -1 file1 file2 Compare the contents of two files and delete only 'file1' Content included comm -2 file1 file2 Compare the contents of two files and delete only 'file2' Content included comm -3 file1 file2 Compare the contents of two files and delete only the parts common to the two files
Packaging and compressing files
- The tar command packages the files. By default, the files will not be compressed. If the corresponding parameters are specified, it will also call the corresponding compression programs (such as gzip and bzip) for compression and decompression
-c : New package file -t : See what file names are included in the contents of the packaged file -x : Unpacking or decompression functions can be matched-C((in uppercase) specify the directory to extract. Note:-c,-t,-x Cannot appear in the same command at the same time -j : adopt bzip2 Support for compression/decompression -z : adopt gzip Support for compression/decompression -v : In compression/During decompression, the file name being processed is displayed -f filename : filename For files to process -C dir : Specify compression/Unzipped directory dir
Compression: tar -jcv -f filename.tar.bz2 file or directory name to be processed query: tar -jtv -f filename.tar.bz2 decompression: tar -jxv -f filename.tar.bz2 -C directory to be decompressed
bunzip2 file1.bz2 Unzip a file called 'file1.bz2'File bzip2 file1 Compress one called 'file1' File gunzip file1.gz Unzip a file called 'file1.gz'File gzip file1 Compress one called 'file1'File gzip -9 file1 Maximum compression rar a file1.rar test_file Create one called 'file1.rar' My bag rar a file1.rar file1 file2 dir1 Simultaneous compression 'file1', 'file2' And catalog 'dir1' rar x file1.rar decompression rar package zip file1.zip file1 Create a zip Compressed package in format unzip file1.zip Unzip one zip Format compressed package zip -r file1.zip file1 file2 dir1 Compress several files and directories into one at the same time zip Compressed package in format
System shutdown (shutdown, restart and logout)
shutdown -h now Shut down the system(1) init 0 Shut down the system(2) telinit 0 Shut down the system(3) shutdown -h hours:minutes & Shut down the system at a predetermined time shutdown -c Cancel system shutdown at scheduled time shutdown -r now restart(1) reboot restart(2) logout cancellation time Measure the execution time of a command (i.e. program)
Process related commands
- jps command, which displays the java process of the current system and its id number
jps(Java Virtual Machine Process Status Tool) is a command provided by JDK 1.5 to display the pid of all current java processes. It is simple and practical. It is very suitable for simply viewing some simple situations of current java processes on linux/unix platform. - ps command is used to select and output the process operation at a certain point in time. It means process
-A : All processes are displayed -a : Not with terminal All processes related to -u : Processes related to valid users -x : General and a Parameters can be used together to list more complete information -l : Longer, more detailed PID Information list for ps aux # View all process data of the system ps ax # View all processes not related to terminal ps -lA # View all process data of the system ps axjf # View the status of a part of the process tree
- The kill command is used to send a signal to a job (% jobnumber) or a PID (number). It is usually used together with ps and jobs commands. The command format is: kill [command parameter] [process id]
Command parameters:
-l Signal. If the number parameter of the signal is not added, it is used“-l"The parameter lists all signal names -a When processing the current process, the correspondence between command name and process number is not limited -p appoint kill The command prints only the process number of the related process without sending any signal -s Specify send signal -u Designated user
Example 1: list all signal names command: kill -l output:
[root@localhost test6]# kill -l 1) SIGHUP 2) SIGINT 3) SIGQUIT 4) SIGILL 5) SIGTRAP 6) SIGABRT 7) SIGBUS 8) SIGFPE 9) SIGKILL 10) SIGUSR1 11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM 16) SIGSTKFLT 17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP 21) SIGTTIN 22) SIGTTOU 23) SIGURG 24) SIGXCPU 25) SIGXFSZ 26) SIGVTALRM 27) SIGPROF 28) SIGWINCH 29) SIGIO 30) SIGPWR 31) SIGSYS 34) SIGRTMIN 35) SIGRTMIN+1 36) SIGRTMIN+2 37) SIGRTMIN+3 38) SIGRTMIN+4 39) SIGRTMIN+5 40) SIGRTMIN+6 41) SIGRTMIN+7 42) SIGRTMIN+8 43) SIGRTMIN+9 44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13 48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12 53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9 56) SIGRTMAX-8 57) SIGRTMAX-7 58) SIGRTMAX-6 59) SIGRTMAX-5 60) SIGRTMAX-4 61) SIGRTMAX-3 62) SIGRTMAX-2 63) SIGRTMAX-1 64) SIGRTMAX
explain:
Only the 9th Signal (SIGKILL) can unconditionally terminate the process, and other signal processes have the right to ignore. The following are common signals:
HUP 1 Terminal disconnection INT 2 Interrupt (same as Ctrl + C) QUIT 3 Exit (same as Ctrl + \) TERM 15 termination KILL 9 Compulsory termination CONT 18 Continue (with STOP contrary, fg/bg (command) STOP 19 Pause (same as Ctrl + Z)
Example 2: get the value of the specified signal
[root@localhost test6]# kill -l KILL [root@localhost test6]# kill -l SIGKILL [root@localhost test6]# kill -l TERM [root@localhost test6]# kill -l SIGTERM [root@localhost test6]#
Example 3: first find the process with ps, and then kill it with kill
Command: kill 3268 [root@localhost test6]# ps -ef|grep vim root 3268 2884 0 16:21 pts/1 00:00:00 vim install.log root 3370 2822 0 16:21 pts/0 00:00:00 grep vim [root@localhost test6]# kill 3268
Example 4: completely kill the process
Command: kill –9 3268 // -9 force kill process
- Kill Command sends a signal to the process started by a command to kill the process with the specified name
Command format: kill [command parameter] [process name]
Command parameters: -Z Kill only those who have scontext Process of -e Matching process name is required -I Ignore lowercase -g Kill process groups instead of processes -i Interactive mode, ask the user before killing the process -l List all known signal names -q Do not output warning information -s Send the specified signal -v Whether the report signal is successfully sent -w Wait for the process to die --help display help information --version Display version display
Example
1: Kill all processes with the same name
killall nginx
killall -9 bash
2.Sends the specified signal to the process
killall -TERM ngixn perhaps killall -KILL nginx
- top command is a commonly used performance analysis tool under Linux. It can display the resource occupation of each process in the system in real time, similar to the task manager of Windows.
How to kill a process:
(1)Graphical interface (2)kill -9 pid (-9 (indicates forced shutdown) (3)killall -9 Program name (4)pkill Program name
View process port number:
netstat -tunlp|grep Port number