search command
file search command
1. Command name: which
Command path: /usr/bin/which
Execution authority: all users
Function description: Search the directory and alias where the system command is located
Syntax: which [command name]
Ex:which ls
2.. Command name: whereis
Command path: /usr/bin/whereis
Execution authority: All users
Function description: The path where the search command (only system commands are found) and the location of the help documentation
Syntax: whereis [command name]
Options:
-b: Find executable files
only -m: Find help files only
Ex:whereis -b ls
whereis -m ls
Note: (The cd command shell comes with it, so the file cannot be found through this)
file search command
1. Command name: findCommand path: /usr/bin/find
Execution permission: all users
Function description: Find a file or directory
Syntax: find [search path] [search keyword]
There are many search keywords for the find command, some of which are introduced below
find /etc -name init
finds files with the name init in the directory /etc, the -name option is based on the name search
find / -size +204800
finds files larger than 100 M in the root directory, the -size option is based on the size Retrieve
find / -user sam to find files with owner sam in the root directory, -user is to retrieve find /etc -ctime -1
based on username
Find files or directories whose attributes have been modified within 24 hours under /etc
Here -ctime is based on the number of days to retrieve, -1 is within one day, +1 is one day ago
- atime file access time
-ctime change file attribute time.
-mtime change file content time
Can also be cmin amin mmin means minutes
find /etc -size +163840 -a -size -204800
Find files larger than 80M and smaller than 100M under /etc
#The 80 megabytes and 100 megabytes are calculated according to the minimum unit of the Linux file system is 512b, for example, the unit of 204800 is 512b
then its so 204800*512b/1024*1024=100M
find /etc -name inittab -exec Is -l {} \;
Find the inittab file under /etc and display the details
#: exec command{} \;You can put it after any command to continue executing the command after exec
For example, in this example, find will find things into {}, and then ls will display them. When exec is replaced with -ok, the same effect can be achieved, but each time it asks whether it is how or not. This works great when deleting
find /root -nouser
finds files without an owner
#Explanation: ------- A file without an owner is a garbage file in Linux, but it is
generated by the kernel in sys and proc and cannot be regarded as a file. In addition, foreign files such as CD-ROM, U disk, etc. cannot be deleted. In addition to this, non-user files
All are junk files and can be deleted.
2. Command name: locate
Command original meaning: list files in databases
Command path: /usr/bin/locate
Execution authority: all users
Function description: Find files and directories
Syntax: locate [command name]
Ex:locate file
list all files with file Related Documents
#Note
locate file name (can only search by file name, not by size, file type, etc.)
The background database searched by the locate command------so locate generally cannot search for newly created files in real time, because
it is necessary to update the database before searching. The search is in the /var/lib/mlocate directory, so Benefits are
Can be faster. (usually update the database one day)
The command to update the data road is:
updatedb
3. Command name: grep
command original meaning:
command path: /bin/grep
execution authority: all users
Function description: search the file for the line matching the string and output
Syntax: grep [specified character] [source file]
Options:
-i ignore case
-v exclude the specified string, even if it means negated
Ex:grep ftp /etc/services
help command
1.
Command name: man
Command original meaning: manual
command path: /usr/bin/man
Execution authority: all users
Function description: Get help information
Syntax: man [command or configuration file]
Ex: man ls
View the help information of the Is command
man services
View the help letter for the configuration file services
2. Command --help #Get
help command
such as
ls --help
help shell internal command #Get
shell internal command
. whereis cd #Determine
whether it is an internal command
. help cd ------ can only get internal commands, but no command location in bin subdirectory
# get internal commands
3. Command name: info
Command original meaning: information
Command path: /usr/bin/info
Execution authority: All users
Function description: Get help information
Syntax: info [any keyword]
Ex:info ls
View help information for the Is command
Compression and decompression command:
Before writing common commands, I want to popularize a knowledge, although many people do not need my popularization, that is, the definitions of packaging, unpacking and compression and decompression
Packing: that is to organize different folders or files into one folder, unpacking is the opposite
Compression: It is to recombine files or folders into a smaller file according to certain rules according to a certain algorithm, and decompression is the opposite.
The following are commonly used commands, which do not follow the above format.
Commonly used compression formats
1----: .zip .gz .bz2
2----: .tar.gz .tar.bz2
1) zip compressed file name source file
#compress file
zip -r compressed file name source directory
#compress Directory
(zip is the same as Windows, and can be transferred to each other)
decompress:
unzip compressed file -d directory Compress the file into the directory #decompress
the .zip file
2) gzip source file
# compress the compressed file in .gz format, The source file will disappear
gzip -c source file > compress file
#compress to .gz format, the source file retains
gzip -r directory
#all sub-files in the compressed directory, but the directory cannot be compressed.
gzip -d compresses files
#decompress the file
gunzip compressed file
#decompress the file
gunzip -r compress the directory #decompress
the compressed file in the directory
3) bzip2 source file
#compress to .bz2 format, do not keep the source file
bzip2 -k source file #retain the source file
after compression
Note: The bzip2 command cannot compress the directory
bzip2 -d compressed file #decompress
, -k keep compressed file
bunzip2 compressed file #compress
file, -k keep compressed file
4)
tar -cvf package file name source file
option
-c: package
-v : show process
-f ; specify the name of the packaged file
. For example
tar -cvf longzls.tar longzls
unpacking command
tar -xvf packing file name
option;
-x : unpacking
5) tar -jcvf archive name .tar.bz2 source file
option
-j : compressing to .tar.bz2 format
tar - jxvf archive name.tar.bz2
#decompress
6) tar -zcvf archive name.tar.bz2 source file
option
-z: compress to .tar.bz2 format
tar -zxvf archive name.tar.bz2 #decompress
tar
- zxvf
archive name.tar.bz2 -C directory-------extract to
the specified directory
tar -ztvf archive name.tar.bz2
Options
-t; view the compressed file, but modify
Description: The f command must be placed after options such as zcvtj, otherwise an error will be reported.
network communication commands
1. Command name: write
Command original meaning:
command path: /usr/bin/write
Execution authority: all users
Function description: Send a message to another user, ending with ctrl+D
Syntax:
write <username>
Ex:write webmaster
2. Command name: wall
command original meaning:
command path: /usr/bin/wall
Execute permission: all users
Function description: broadcast information to all users
Syntax:
wall [message] [filename]
Ex:wall Happy New Year
3. Command name: ping
command original meaning:
command path: /usr/sbin/ping
Execute permission: all users
Function description: Test network connectivity
Syntax:
ping 192.168.1.120
4. Command name: ifconfig
Command original meaning:
Command path: /usr/sbin/ifconfig
Execution authority: root
Function description: View network setting information
Syntax:
ifconfig option [network card device identification]
-a Display all network card information
Ex:ifconfig -a
Linux Shutdown and Restart Commands
shutdown [options] time (can be now, or a specified time) (&: if you add an and symbol after it, it means it can be placed in the background without affecting the current terminal, if not, you can add Ctrl+c to stop current command)
option;
-c: cancel the previous shutdown command
-h: shutdown
-r: restart (date is; the command to get the current time in Linux)
other shutdown commands
halt Enter-----shutdown
poweroff Enter -----Shut down
init 0 Enter -----Shut down
(these three are not particularly safe, try to shutdown)
Other reboot commands
reboot