Linux Common Commands — English Explanation
参考文档：菜鸟教程 https://www.runoob.com/w3cnote/linux-common-command-2.html
- ls
Meaning: list files and directories.
You use ls to see what is inside a folder. It can also show hidden files, file permissions, file size, and modification time.
Common options:
ls -a → show all files, including hidden ones
ls -l → show detailed information
ls -h → show file sizes in human-readable form
ls -t → sort by modification time
ls -S → sort by file size
Example:
ls -lhrt
This means:
-l detailed list
-h readable sizes
-r reverse order
-t sort by time
- cd
Meaning: change directory.
Used to move from one folder to another.
Examples:
cd /
Go to the root directory.
cd ~
Go to the home directory.
cd -
Go back to the previous directory.
- pwd
Meaning: print working directory.
It shows your current directory path.
Example:
pwd
pwd -P
Shows the real path, not the symbolic link path.
- mkdir
Meaning: make directory.
Used to create new folders.
Examples:
mkdir t
Create a folder named t.
mkdir -p /tmp/test/t1/t
Create nested directories at once.
-p means create parent directories if needed.
- rm
Meaning: remove files or directories.
Examples:
rm -i *.log
Delete .log files, but ask for confirmation first.
rm -rf test
Delete the test directory and everything inside it.
-r recursive
-f force
This command is powerful and dangerous.
- rmdir
Meaning: remove empty directories only.
Example:
rmdir -p parent/child/child11
Delete the last empty directory, and also remove parent directories if they become empty.
- mv
Meaning: move or rename files.
Examples:
mv test.log test1.txt
Rename test.log to test1.txt.
mv log1.txt log2.txt log3.txt /test3
Move multiple files into /test3.
- cp
Meaning: copy files or directories.
Examples:
cp -ai a.txt test
Copy a.txt to test, keep original time, and ask before overwriting.
cp -s a.txt link_a.txt
Create a symbolic link to a.txt.
- cat
Meaning: display file content, create files, or combine files.
Examples:
cat filename
Display the whole file.
cat > filename
Create a new file from keyboard input.
cat file1 file2 > file
Combine two files into one.
Also:
cat -n → show line numbers
cat -b → show line numbers only for non-empty lines
- more
Meaning: view a file page by page.
Useful when a file is too long for one screen.
Example:
more +3 text.txt
Start showing the file from line 3.
You can press:
Space → next page
b → previous page
q → quit
- less
Meaning: better file viewer than more.
It lets you scroll forward and backward more freely.
Examples:
less 1.log 2.log
Open multiple files.
Useful keys:
/text → search forward
?text → search backward
n → next match
N → previous match
Q → quit
- head
Meaning: show the beginning of a file.
Example:
head -n 20 1.log
Show the first 20 lines.
- tail
Meaning: show the end of a file.
Example:
tail -f ping.log
Continuously monitor new content added to a log file.
Very useful for watching logs in real time.
- which
Meaning: find the location of an executable command.
Example:
which ls
Shows where the ls command is located.
It only searches commands in the PATH.
- whereis
Meaning: find the binary file, source code, and manual page of a command.
Example:
whereis locate
Compared with which, whereis gives more related locations.
- locate
Meaning: quickly search for files by name using a database.
Example:
locate pwd
It is fast, but may miss very new files because it depends on a database that updates periodically.
- find
Meaning: search files and directories in the file system.
This is one of the most important Linux commands.
Examples:
find ./ -name '*.log'
Find all .log files in the current directory.
find /opt -perm 777
Find files with permission 777.
find . -type f -mtime +10 -exec rm -f {} \;
Find files older than 10 days and delete them.
find can search by:
name
type
size
time
owner
permissions
It can also run commands on the results using -exec.
- chmod
Meaning: change file permissions.
Linux permissions include:
r = read
w = write
x = execute
Examples:
chmod a+x t.log
Give execute permission to everyone.
chmod 751 t.log
Set permissions numerically:
owner = 7 = rwx
group = 5 = r-x
others = 1 = --x
- tar
Meaning: archive files, and often compress them.
Important idea:
archive = pack many files into one
compress = reduce file size
Examples:
tar -zcvf /tmp/etc.tar.gz /etc
Create a compressed archive of /etc.
tar -ztvf /tmp/etc.tar.gz
List contents of a compressed archive.
Common options:
-c create
-x extract
-t list contents
-f specify filename
-z gzip
-j bzip2
-v verbose
- chown
Meaning: change file owner and group.
Examples:
chown -c mail:mail log2012.log
Change the owner and group to mail.
chown -cR mail: test/
Recursively change ownership for a directory.
- df
Meaning: display disk space usage.
Example:
df -haT
Show all file systems, in readable format, with file system type.
Use this to check how much disk space is left.
- du
Meaning: show disk usage of files and directories.
Example:
du -ah scf/
Show the size of all files and subdirectories.
du -hc test/ scf/
Show sizes plus a total.
Difference:
df = disk free space of the whole filesystem
du = size used by specific files/folders
- ln
Meaning: create links.
Two types:
soft link (ln -s) = like a shortcut
hard link = another name for the same file data
Examples:
ln -sv source.log link.log
Create a symbolic link.
ln -v source.log link1.log
Create a hard link.
- date
Meaning: display or set the system date and time.
Examples:
date
Show current date and time.
date -d tomorrow +%Y%m%d
Show tomorrow’s date in YYYYMMDD format.
Useful for scripts.
- cal
Meaning: display a calendar.
Examples:
cal 9 2012
Show the calendar for September 2012.
cal -y 2013
Show the full calendar for 2013.
- grep
Meaning: search text by pattern.
This is one of the most useful commands in Linux.
Examples:
ps -ef | grep svn
Search for processes containing svn.
grep -lR '^grep' /tmp
Recursively find files in /tmp whose content starts with grep.
Useful options:
-i ignore case
-n show line numbers
-c count matches
-R recursive search
- wc
Meaning: count lines, words, and bytes.
Example:
wc text.txt
Shows:
number of lines
number of words
number of bytes
filename
cat test.txt | wc -l
Count lines in output.
- ps
Meaning: show current running processes.
Examples:
ps -ef
Show all processes in full format.
ps -aux | grep apache
Find the Apache process.
This command helps you inspect what programs are running.
- top
Meaning: dynamic process monitor.
It shows:
CPU usage
memory usage
running processes
system load
It updates in real time.
Useful interactive keys:
P sort by CPU
m sort by memory
c show full command line
h help
- kill
Meaning: send a signal to a process.
Example:
kill -9 PID
Forcefully stop a process.
-9 means SIGKILL, which cannot be ignored.
Safer default:
kill PID
This sends SIGTERM first.
- free
Meaning: show memory usage.
Examples:
free -m
Show memory usage in MB.
free -s 10
Refresh every 10 seconds.
Useful for checking RAM and swap usage.
Main idea of the whole article
This article is trying to teach basic Linux command-line operations.
It covers 4 major areas:
- File and directory operations
Examples:
ls
cd
pwd
mkdir
rm
mv
cp
- File viewing and searching
Examples:
cat
more
less
head
tail
grep
find
- System monitoring
Examples:
ps
top
free
df
du
- Permissions and archive management
Examples:
chmod
chown
tar
ln
A more natural English summary
You could describe this page like this:
This article introduces commonly used Linux commands for beginners. It explains how to navigate directories, manage files, search for content, check system resources, change file permissions, and handle processes. These commands are essential for daily Linux usage and system administration.
中文意思：
这篇文章向初学者介绍了常用的 Linux 命令，内容包括目录切换、文件管理、内容搜索、系统资源查看、权限修改以及进程管理。这些命令是日常使用 Linux 和进行系统管理的基础。
If you want to study this efficiently
I’d group them like this:
Must learn first
ls
cd
pwd
mkdir
rm
cp
mv
cat
Very practical next
grep
find
head
tail
less
For system monitoring
ps
top
df
du
free
For admin tasks
chmod
chown
kill
tar
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