Learn Together for a Lifetime Here is Programmer Android

This article mainly introduces some knowledge points in Android development. By reading this article, you will gain the following content:

1. cd command 2. –help command 3. ls command 4. touch command 5. mkdir command 6. pwd command 7. echo command 8. cat command 9. Tab key 10. vi or vim command 11. rm command 12. mv command 13. cp command 14. find command 15. grep command 16. chmod command 17. Compression and decompression commands 18. Top command 19. Find strings in a specific type of file (e.g., *.xml) 20. String replacement command 21. Tree command 22. Display all files in a directory 23. Count the number of files in a directory

1. cd Command

The cd command is one of the commonly used commands in Linux, mainly used to enter a directory (equivalent to a folder in Windows). For example, if I want to enter the TestLinuxCommond directory, I can use cd TestLinuxCommond/

programAndroid@ubuntu:~$ cd TestLinuxCommond/
programAndroid@ubuntu:~/TestLinuxCommond$ 

If I want to exit the TestLinuxCommond directory, I can use cd ..

programAndroid@ubuntu:~/TestLinuxCommond$ cd ..
programAndroid@ubuntu:~$ 

If I want to go back two levels, I can use cd ../..

programAndroid@ubuntu:~/TestLinuxCommond/testmv/test$ ls
programAndroid@ubuntu:~/TestLinuxCommond/testmv/test$ cd ../..
programAndroid@ubuntu:~/TestLinuxCommond$ 

2. –help Command

When we do not know how to use a command, we can use --help to see what this command does. --help is equivalent to a user command help manual. For example, if I want to see how to use the cd command, I can use cd ---help

programAndroid@ubuntu:~/TestLinuxCommond$ cd ---help
-bash: cd: --: invalid option
cd: usage: cd [-L|[-P [-e]] [-@]] [dir]
programAndroid@ubuntu:~/TestLinuxCommond$ 

If I want to see how to use the ls command and what parameters it has, I can use ls ---help

programAndroid@ubuntu:~/TestLinuxCommond$ ls --help
Usage: ls [OPTION]... [FILE]...
List information about the FILEs (the current directory by default).
Sort entries alphabetically if none of -cftuvSUX nor --sort is specified.

Mandatory arguments to long options are mandatory for short options too.
  -a, --all                  do not ignore entries starting with .
  -A, --almost-all           do not list implied . and ..
      --author               with -l, print the author of each file
  -b, --escape               print C-style escapes for nongraphic characters
      --block-size=SIZE      scale sizes by SIZE before printing them.  E.g.,
                               '--block-size=M' prints sizes in units of
                               1,048,576 bytes.  See SIZE format below.
  -B, --ignore-backups       do not list implied entries ending with ~
  -c                         with -lt: sort by, and show, ctime (time of last
                               modification of file status information)
                               with -l: show ctime and sort by name
                               otherwise: sort by ctime, newest first
  -C                         list entries by columns
      --color[=WHEN]         colorize the output.  WHEN defaults to 'always'
                               or can be 'never' or 'auto'.  More info below
  -d, --directory            list directory entries instead of contents,
                               and do not dereference symbolic links
  -D, --dired                generate output designed for Emacs' dired mode
  -f                         do not sort, enable -aU, disable -ls --color
  -F, --classify             append indicator (one of */=>@|) to entries
      --file-type            likewise, except do not append '*'
      --format=WORD          across -x, commas -m, horizontal -x, long -l,
                               single-column -1, verbose -l, vertical -C
      --full-time            like -l --time-style=full-iso
  -g                         like -l, but do not list owner
      --group-directories-first
                             group directories before files.
                               augment with a --sort option, but any
                               use of --sort=none (-U) disables grouping
  -G, --no-group             in a long listing, don't print group names
  -h, --human-readable       with -l, print sizes in human readable format
                               (e.g., 1K 234M 2G)
      --si                   likewise, but use powers of 1000 not 1024
  -H, --dereference-command-line
                             follow symbolic links listed on the command line
      --dereference-command-line-symlink-to-dir
                             follow each command line symbolic link
                             that points to a directory
      --hide=PATTERN         do not list implied entries matching shell PATTERN
                               (overridden by -a or -A)
      --indicator-style=WORD  append indicator with style WORD to entry names:
                               none (default), slash (-p),
                               file-type (--file-type), classify (-F)
  -i, --inode                print the index number of each file
  -I, --ignore=PATTERN       do not list implied entries matching shell PATTERN
  -k, --kibibytes            use 1024-byte blocks
  -l                         use a long listing format
  -L, --dereference          when showing file information for a symbolic
                               link, show information for the file the link
                               references rather than for the link itself
  -m                         fill width with a comma separated list of entries
  -n, --numeric-uid-gid      like -l, but list numeric user and group IDs
  -N, --literal              print raw entry names (don't treat e.g. control
                               characters specially)
  -o                         like -l, but do not list group information
  -p, --indicator-style=slash
                             append / indicator to directories
  -q, --hide-control-chars   print ? instead of non graphic characters
      --show-control-chars   show non graphic characters as-is (default
                             unless program is 'ls' and output is a terminal)
  -Q, --quote-name           enclose entry names in double quotes
      --quoting-style=WORD   use quoting style WORD for entry names:
                               literal, locale, shell, shell-always, c, escape
  -r, --reverse              reverse order while sorting
  -R, --recursive            list subdirectories recursively
  -s, --size                 print the allocated size of each file, in blocks
  -S                         sort by file size
      --sort=WORD            sort by WORD instead of name: none -U,
                             extension -X, size -S, time -t, version -v
      --time=WORD            with -l, show time as WORD instead of modification
                             time: atime -u, access -u, use -u, ctime -c,
                             or status -c; use specified time as sort key
                             if --sort=time
      --time-style=STYLE     with -l, show times using style STYLE:
                             full-iso, long-iso, iso, locale, +FORMAT.
                             FORMAT is interpreted like 'date'; if FORMAT is
                             FORMAT1<newline>FORMAT2, FORMAT1 applies to
                             non-recent files and FORMAT2 to recent files;
                             if STYLE is prefixed with 'posix-', STYLE
                             takes effect only outside the POSIX locale
  -t                         sort by modification time, newest first
  -T, --tabsize=COLS         assume tab stops at each COLS instead of 8
  -u                         with -lt: sort by, and show, access time
                               with -l: show access time and sort by name
                               otherwise: sort by access time
  -U                         do not sort; list entries in directory order
  -v                         natural sort of (version) numbers within text
  -w, --width=COLS           assume screen width instead of current value
  -x                         list entries by lines instead of by columns
  -X                         sort alphabetically by entry extension
  -Z, --context              print any SELinux security context of each file
  -1                         list one file per line
      --help     display this help and exit
      --version  output version information and exit

SIZE is an integer and optional unit (example: 10M is 10*1024*1024).  Units
are K, M, G, T, P, E, Z, Y (powers of 1024) or KB, MB, ... (powers of 1000).

Using color to distinguish file types is disabled both by default and
with --color=never.  With --color=auto, ls emits color codes only when
standard output is connected to a terminal.  The LS_COLORS environment
variable can change the settings.  Use the dircolors command to set it.

Exit status:
 0  if OK,
 1  if minor problems (e.g., cannot access subdirectory),
 2  if serious trouble (e.g., cannot access command-line argument).

Report ls bugs to [email protected]
GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
General help using GNU software: <http://www.gnu.org/gethelp/>
For complete documentation, run: info coreutils 'ls invocation'
programAndroid@ubuntu:~/TestLinuxCommond$ 

3. ls Command

The ls command is used to display the files or directories (called folders in Windows) in the current directory. Note: Using ls -l can display all contents of the current directory in a list format, along with detailed information about the files. For example, if I want to see what files are in the current directory, I can use ls.

programAndroid@ubuntu:~/TestLinuxCommond$ ls
test.txt
programAndroid@ubuntu:~/TestLinuxCommond$

If I want to see detailed information about the files in the current directory, I can use ls -l

programAndroid@ubuntu:~/TestLinuxCommond$ ls -l
total 0
-rw-rw-r-- 1 programAndroid programAndroid 0 Jul 18 16:24 test.txt
programAndroid@ubuntu:~/TestLinuxCommond$

4. touch Command

The touch command is used to create text files, which can have extensions or not, depending on personal preference. For example, if I want to create a testlinux.txt file, I can use touch testlinux.txt

programAndroid@ubuntu:~/TestLinuxCommond$ touch testlinux.txt
programAndroid@ubuntu:~/TestLinuxCommond$ ls
testlinux.txt  test.txt
programAndroid@ubuntu:~/TestLinuxCommond$

5. mkdir Command

The mkdir command is used to create directories, which in Linux are equivalent to folders in Windows. For example, if I want to create a test directory, I can use mkdir test

programAndroid@ubuntu:~/TestLinuxCommond$ mkdir test
programAndroid@ubuntu:~/TestLinuxCommond$ ls
test  testlinux.txt  test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ 

6. pwd Command

The pwd command is used to display the path of the current directory. For example, if I want to see what the path of my current directory is, I can use pwd

programAndroid@ubuntu:~/TestLinuxCommond$ pwd
/home/programAndroid/TestLinuxCommond
programAndroid@ubuntu:~/TestLinuxCommond$ 

7. echo Command

The echo command is mainly used to append content to text files. For example, if I want to write hello Linux into the testlinux.txt file, I can use echo "hello Linux" > testlinux.txt

programAndroid@ubuntu:~/TestLinuxCommond$ echo "hello Linux" > testlinux.txt 
programAndroid@ubuntu:~/TestLinuxCommond$ cat testlinux.txt 
hello Linux
programAndroid@ubuntu:~/TestLinuxCommond$ 

8. cat Command

The cat command is mainly used to display the contents of text files. For example, if I want to display the contents of testlinux.txt , I can use cat testlinux.txt

programAndroid@ubuntu:~/TestLinuxCommond$ cat testlinux.txt 
hello Linux
programAndroid@ubuntu:~/TestLinuxCommond$ 

9. Tab Key

The Tab key in Linux is mainly used to assist input and provide a quick completion function. For example, if we want to see the directories or files starting with test in the current directory, but we forget the full name of the file or directory, we can press the Tab key after entering the beginning, and the system will list all files or directories starting with test. Here is an example:

programAndroid@ubuntu:~/TestLinuxCommond$ ls test
test/          testlinux.txt  test.txt       
programAndroid@ubuntu:~/TestLinuxCommond$ 

10. vi or vim Command

The vi or vim command is mainly used to edit text files through the vim editor. For example, if we want to edit the testlinux.txt file, we can use vim testlinux.txt or vim testlinux.txt. After entering the command, you need to press i or a to perform input operations on the text file.

1. Press i or a to insert into the text file

2. Press the Esc key, then enter : to save the file

Command	Meaning
w	Save
q	Exit
!	Force
wq	Save and exit
q!	Discard changes and force exit

3. set nu to display line numbers, set nonu to cancel displaying line numbers

Usage format: set nu or set nonu

set nu

4. /search_string is used to search for strings

Usage format: /search_string For example, to search for e, pressing N key can globally switch between searching for the previous and next strings.

/search_string

11. rm Command

The rm command is mainly used to delete files or directories, noting that there is a difference between the two.

Delete files

Usage format: rm filename For example, if I want to delete test.txt, I can use rm test.txt

programAndroid@ubuntu:~/TestLinuxCommond$ ls
test  testlinux.txt  test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ rm test.txt 
programAndroid@ubuntu:~/TestLinuxCommond$ ls
test  testlinux.txt
programAndroid@ubuntu:~/TestLinuxCommond$ 

Delete directories

Usage format: rm -r filename When deleting a directory, you need to add the -r parameter, which is mainly used to recursively delete all contents within the directory (including directories, files, etc.). For example, if I want to delete the test directory

programAndroid@ubuntu:~/TestLinuxCommond$ ls
test  testlinux.txt
programAndroid@ubuntu:~/TestLinuxCommond$ rm test
rm: cannot remove ‘test’: Is a directory
programAndroid@ubuntu:~/TestLinuxCommond$ ls
test  testlinux.txt
programAndroid@ubuntu:~/TestLinuxCommond$ rm -r test
programAndroid@ubuntu:~/TestLinuxCommond$ ls
testlinux.txt
programAndroid@ubuntu:~/TestLinuxCommond$ 

12. mv Command

The mv command is mainly used to move or rename files.

Rename

Usage format: mv old_filename new_filename For example, if I want to rename testlinux.txt to test.txt, I can use mv testlinux.txt test.txt as shown below:

programAndroid@ubuntu:~/TestLinuxCommond$ mkdir testmv
programAndroid@ubuntu:~/TestLinuxCommond$ ls
testlinux.txt  testmv
programAndroid@ubuntu:~/TestLinuxCommond$ mv testlinux.txt  test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ ls
testmv  test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ 

Move

Usage format: mv file_to_move destination_directory For example, if I want to move test.txt from the current directory to the testmv directory, I can use mv test.txt testmv/

programAndroid@ubuntu:~/TestLinuxCommond$ ls
testmv  test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ mv test.txt testmv/
programAndroid@ubuntu:~/TestLinuxCommond$ ls
testmv
programAndroid@ubuntu:~/TestLinuxCommond$ cd testmv/
programAndroid@ubuntu:~/TestLinuxCommond/testmv$ ls
test  test.txt
programAndroid@ubuntu:~/TestLinuxCommond/testmv$ 

13. cp Command

Usage format: cp file_to_copy destination_directory The cp command is used to copy files. For example, if I want to copy test.txt to the test directory, I can use cp test.txt test

programAndroid@ubuntu:~/TestLinuxCommond/testmv$ ls
test  test.txt
programAndroid@ubuntu:~/TestLinuxCommond/testmv$ cp test.txt test
programAndroid@ubuntu:~/TestLinuxCommond/testmv$ cd test/
programAndroid@ubuntu:~/TestLinuxCommond/testmv/test$ ls
test.txt
programAndroid@ubuntu:~/TestLinuxCommond/testmv/test$ 

To copy and include detailed directory information, use the following method:

programAndroid@programAndroid:$  cp --parents -av   tools/releasetools/build_image.py   /programAndroid/log/ 

14. find Command

The find command is used to search for files. For example, if I want to find a file named test.txt in the current directory, I can use find . -name test.txt command to search. Here is an example:

programAndroid@ubuntu:~/TestLinuxCommond$ find . -name test.txt
./testmv/test.txt
./testmv/test/test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ 

To find a path that includes three levels of directories, use the following command:

find /home/test -type d -maxdepth 3

15. grep Command

The grep command is used to search for string resources in files.

Case-sensitive

For example, if I want to search for the string Sprocomm, I can use grep "Sprocomm" -r . This search is strictly case-sensitive.

programAndroid@ubuntu:~/TestLinuxCommond$ grep "Sprocomm" -r .
./testmv/test.txt:Welcome to Sprocomm
./testmv/test/test.txt:Welcome to Sprocomm
programAndroid@ubuntu:~/TestLinuxCommond$ 

Case-insensitive

Add -i to ignore case sensitivity. For example, if I want to search for the string Sprocomm, I can use grep "Sprocomm" -ri .

programAndroid@ubuntu:~/TestLinuxCommond$ grep "sprocomm" -r .
programAndroid@ubuntu:~/TestLinuxCommond$ grep "sprocomm" -ri .
./testmv/test.txt:Welcome to Sprocomm
./testmv/test/test.txt:Welcome to Sprocomm

16. chmod Command

The chmod command is mainly used to modify the permissions of directories or files.

programAndroid@ubuntu:~/TestLinuxCommond$ ls -l
total 4
drwxrwxr-x 3 programAndroid programAndroid 4096 Jul 18 17:56 testmv
programAndroid@ubuntu:~/TestLinuxCommond$ 

Name	Abbreviation	Meaning	Value
d	dir	Directory	–
r	read	Read file permission	4
w	write	Write file permission	2
x	–	Executable permission (usually for sh scripts, library files, etc.)	1

If I want to change the read, write, and execute permissions for all files in the testmv directory, I can use chmod 777 -R .

programAndroid@ubuntu:~/TestLinuxCommond$ ls -l
total 4
drwxrwxr-x 3 programAndroid programAndroid 4096 Jul 18 17:56 testmv
programAndroid@ubuntu:~/TestLinuxCommond$ chmod 777 -R .
programAndroid@ubuntu:~/TestLinuxCommond$ ls -l
total 4
drwxrwxrwx 3 programAndroid programAndroid 4096 Jul 18 17:56 testmv
programAndroid@ubuntu:~/TestLinuxCommond$ 

17. Compression and Decompression Commands

tar Compression and Decompression Command

Compression command format: tar -cvf *.tar files_to_compress For example, if I want to compress a testmv.tar , I can use tar -cvf test.tar testmv/

programAndroid@ubuntu:~/TestLinuxCommond$ tar -cvf test.tar testmv/
testmv/
testmv/test.txt
testmv/test/
testmv/test/test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ ls
testmv  test.tar
programAndroid@ubuntu:~/TestLinuxCommond$ 

Decompression command format: tar -xvf test.tar For example, if I want to decompress a test.tar , I can use tar -xvf test.tar

programAndroid@ubuntu:~/TestLinuxCommond$ rm -rf testmv/
programAndroid@ubuntu:~/TestLinuxCommond$ ls
test.tar
programAndroid@ubuntu:~/TestLinuxCommond$ tar -xvf test.tar  
testmv/
testmv/test.txt
testmv/test/
testmv/test/test.txt
programAndroid@ubuntu:~/TestLinuxCommond$ ls
testmv  test.tar
programAndroid@ubuntu:~/TestLinuxCommond$ 

zip Compression Command

programAndroid@programAndroid:/programAndroid/log$ zip  -r test.zip test.bat 
  adding: test.bat (stored 0%)
programAndroid@programAndroid:/programAndroid/log$ 

18. Top Command

Usage of the Top command

adb shell top -n 30 -m 10  -k -%CPU > top1.txt

19. Find Strings in a Specific Type of File (e.g., *.xml)

find . -type f -name "*.xml" | xargs grep "xxx"

20. String Replacement Command

Command to replace all strings in a directory

For example, replace WLAN with WiFi

sed -i 's/WLAN/WiFi/g' `grep WLAN . -rl`

21. Tree Command

E:\AOSP\android_10_0_0_r40\frameworks\av\camera>tree
Volume in drive Document's folder
Volume serial number is 00000233 65F3:3762
E:.
├─aidl
│  └─android
│      └─hardware
│          └─camera2
│              ├─impl
│              ├─params
│              └─utils
├─camera2
├─cameraserver
├─include
│  └─camera
│      ├─android
│      │  └─hardware
│      └─camera2
├─ndk
│  ├─impl
│  ├─include
│  │  └─camera
│  └─ndk_vendor
│      ├─impl
│      └─tests
└─tests

E:\AOSP\android_10_0_0_r40\frameworks\av\camera>

22. Display All Files in a Directory

find -type f -print

Usage example:

$ find -type f -print
./Android.bp
./Barrier.h
./BufferLayer.cpp
./BufferLayer.h
./BufferLayerConsumer.cpp
./BufferLayerConsumer.h
./BufferQueueLayer.cpp
./BufferQueueLayer.h
./BufferStateLayer.cpp
./BufferStateLayer.h

23. Count the Number of Files in a Directory

The command is as follows: ls -lR |grep '^-' |wc -l Usage example:

/e/AOSP/android_10_0_0_r40/frameworks/native/services/surfaceflinger (master)
$ ls -lR |grep '^-' |wc -l
294

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