Date Displays the system date

Curl ifconfig.me Curl ifconfig.me curl ifconfig.me

Disk space:

Df -h Displays the list of mounted partitions

Du -sh dir5 (-s indicates summary) lists only one summary value

Du -ah dir5 (-a indicates directories and files)

File and directory operations:

Ls -l Displays detailed information about files and directories

Ls -l test. TXT Displays details about files and directories

Ls -a Displays hidden files

Ls -f Displays files in the directory

PWD Displays the working path

Mkdir dir1 dir2 Create two directories simultaneously

Mkdir -p/TMP /dir1/dir2 Creates a directory tree

Rm file Drop a file called ‘file’

Rmdir dir delete an empty directory called ‘dir’

Rm -r dir Deletes a directory named ‘dir’ and deletes the files in the directory

Rm -r dir1 dir2 Delete both directories and their contents

Mv dir new_dir Renames or moves a directory

Cp file1 file2 Copies a file

Cp -a dir1 dir2 Copies a directory

Cp -a/TMP/dir1. copy a directory to the current working directory

File search:

Find / -name file Searches for files and directories in the root file system starting with ‘/’

Find /home/user-name *. Bin Searches for files ending in’.bin’ in the directory ‘/home/user’

Log file operations:

Grep ‘2020-07-06 11:3[4-7]’ pay.log Query logs generated between 11:34 and 11:37

Grep -e “word1 | word2 | word3” file. TXT satisfy any conditions (word1 word2, and one of word3) will match.

Grep word1 file. TXT | grep word2 | grep word3 must to satisfy the three conditions “(word1 word2 and word3) to match.

The grep word1 *. The log | grep word2 | more paging view what accords with a condition.

Grep -c 5 foo file Displays the line matching the string foo and the five lines above and below in file

Grep -b 5 foo file Displays foo and the first five lines

Grep -a 5 foo file Displays foo and the next five lines

Grep –color word1 file. TXT Displays the word1 in the query result in color

View file contents:

Cat file1 Forwards the file from the first byte

Tac file1 looks at the contents of a file in reverse, starting with the last line

More file1 Displays the contents of a long file

Less file1 is similar to the ‘more’ command, but it allows the same reverse operation in the file as the forward operation

Head-2 file1 Displays the first two lines of a file

Tail-2 file1 Displays the last two lines of a file

Tail -f /var/log/messages View the contents added to a file in real time

File packaging, compression, and decompression

Packaging is to make a large number of files or directories into a total file; Compression is the process of turning a large file into a small file using some compression algorithms.

Many Linux compressors can compress only one file, so if you want to compress a large number of files, you need to first pack the large number of files into a package (tar) and then use the compression program (gzip bzip2).

Gzip program

Disadvantages: Cannot compress the directory, the original file will be deleted after the compressed file is generated.

Compressed file:

gzip tt.txt

Unzip files:

gunzip tt.txt.gz

Zip program:

Compare with gzip: you can compress directories and keep the original files.

Compressed file:

zip test.zip tt.txt

Compressed directory (always include -r) :

zip -r tt.zip dir5

Unzip files:

unzip test.zip

Tar itself does not have compression. It is implemented by calling other compression functions.

Format of the tar command:

Tar [required parameters][Select parameters][file]

The required parameters are as follows:

-c Creates a new compressed file

-r Adds a file to a compressed file

-x Extracts files from compressed files

-t Displays the contents of compressed files

-z Supports gzip file compression or decompression

-j Supports bzip2 to compress or decompress files

-v Displays the operation process

-k Keeps the original file

-m Indicates that the file is not overwritten

-f(file) Uses archive files or devices. This option is usually mandatory.

Package files :(can be files and directories)

tar -vcf test.tar test.txt tt.txt

Unpack file:

tar -xvf test.tar

Compression:

Tar -zxcf test.gz Dir5 Exception information RTF

Tar -jvcf test.bz2 Dir5 Exception information RTF

Extract:

tar -zxvf test.bz2

tar -jxvf test.bz2

1.1 Searching for logs generated during a certain period of time in log files

sed -n ‘/2018-07-05 13:20:00/,/2018-07-05 13:25:00/p’ logfile.log

1.2 Do not Decompress the GZ File Perform search in the file

gunzip -c logfile.gz | grep ‘test’