- Layer-1: Hardware: It consists of all hardware related information.
- Layer-2: Kernel: This is the core of the Operating System. It is a software that acts as the interface between the hardware and the software. Most of the tasks like memory management, file management, network management, process management, etc., are done by the kernel.
- Layer-3: Shell commands: This is the interface between the user and the kernel. Shell is the utility that processes your requests. When you type in a command at the terminal, the shell interprets the command and calls the program that you want. There are various commands like cp, mv, cat, grep, id, wc, nroff, a.out and more.
- Layer-4: Application Layer: It is the outermost layer that executes the given external applications.
| Sr. no | Command (playlist link https://youtube.com/playlist?list=PLUDwpEzHYYLtjJWMCJJDoPXjeSfzrCF-F&si=Us2oluI9b7WIpafz)) | Description | Command tags |
|---|---|---|---|
| 1 | asismisr@CTIPL-MAC-348 lynxPlayground % cat >myFile.txt hello, im creating the file content during run time. ^C asismisr@CTIPL-MAC-348 lynxPlayground % |
This cat command will allow you to create a file along with entering the content during the execution. once the file content is done, user has to break it. | cat |
| 2 | asismisr@CTIPL-MAC-348 lynxPlayground % cat myfile.txt hello, im creating the file content during run time. asismisr@CTIPL-MAC-348 lynxPlayground % |
this cat command will display the content of the file. | cat |
| 3 | asismisr@CTIPL-MAC-348 lynxPlayground % cat >fileOne.text File one content ^C asismisr@CTIPL-MAC-348 lynxPlayground % cat >fileTwo.txt File two content ^C asismisr@CTIPL-MAC-348 lynxPlayground % cat >fileThree.txt File three content ^C asismisr@CTIPL-MAC-348 lynxPlayground % cat fileOne.text fileTwo.txt fileThree.txt File one content File two content File three content asismisr@CTIPL-MAC-348 lynxPlayground % cat fileOne.text fileTwo.txt File one content File two content asismisr@CTIPL-MAC-348 lynxPlayground % |
we can also use cat command to combine content of multiple files. Note: this command will not create a file with combined content. |
cat |
| 4 | asismisr@CTIPL-MAC-348 lynxPlayground % cat fileOne.text File one content asismisr@CTIPL-MAC-348 lynxPlayground % cat >>fileOne.text Appending the new content to file ^C asismisr@CTIPL-MAC-348 lynxPlayground % cat fileOne.text File one content Appending the new content to file asismisr@CTIPL-MAC-348 lynxPlayground % |
This command can be used to append data into and existing file. | cat |
| 5 | asismisr@CTIPL-MAC-348 lynxPlayground % cat >source.txt This data is precious. ^C asismisr@CTIPL-MAC-348 lynxPlayground % cp source.txt destination.txt asismisr@CTIPL-MAC-348 lynxPlayground % cat destination.txt This data is precious. asismisr@CTIPL-MAC-348 lynxPlayground % |
The cp command will copy the content of one file to another file. - If suppose the Destination file does not exist it will create a new one. - If supose the destination file exist, it will replace the entire content of it with the copied data |
cp |
| 6 | asismisr@CTIPL-MAC-348 lynxPlayground % cat destination.txt This data is precious. asismisr@CTIPL-MAC-348 lynxPlayground % mv destination.txt finalDestination.txt asismisr@CTIPL-MAC-348 lynxPlayground % cat finalDestination.txt This data is precious. asismisr@CTIPL-MAC-348 lynxPlayground % cat destination.txt cat: destination.txt: No such file or directory asismisr@CTIPL-MAC-348 lynxPlayground % |
The mv command can be used for below operations: - Rename the file - rename the directory - Move file from 1 directory to another |
mv |
| 7 | asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text fileThree.txt finalDestination.txt myFile.txt fileThree.text fileTwo.txt lynxCommands.docx source.txt asismisr@CTIPL-MAC-348 lynxPlayground % mkdir mydir asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text fileThree.txt finalDestination.txt myFile.txt source.txt fileThree.text fileTwo.txt lynxCommands.docx mydir asismisr@CTIPL-MAC-348 lynxPlayground % mv mydir yourdir asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text fileThree.txt finalDestination.txt myFile.txt yourdir fileThree.text fileTwo.txt lynxCommands.docx source.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
using mv command to rename a directory | mv |
| 8 | asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text fileTwo.txt myFile.txt fileThree.text finalDestination.txt source.txt fileThree.txt lynxCommands.docx yourdir asismisr@CTIPL-MAC-348 lynxPlayground % cat fileToMove cat: fileToMove: No such file or directory asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text fileTwo.txt myFile.txt fileThree.text finalDestination.txt source.txt fileThree.txt lynxCommands.docx yourdir asismisr@CTIPL-MAC-348 lynxPlayground % touch fileToMove asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text fileTwo.txt source.txt fileThree.text finalDestination.txt yourdir fileThree.txt lynxCommands.docx fileToMove myFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % mv fileToMove yourdir asismisr@CTIPL-MAC-348 lynxPlayground % cd yourdir asismisr@CTIPL-MAC-348 yourdir % ls fileToMove asismisr@CTIPL-MAC-348 yourdir % |
using mv command to Move file from 1 directory to another | mv |
| 9 | asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text fileTwo.txt myFile.txt fileThree.text finalDestination.txt source.txt fileThree.txt lynxCommands.docx yourdir asismisr@CTIPL-MAC-348 lynxPlayground % rm fileTwo.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text finalDestination.txt source.txt fileThree.text lynxCommands.docx yourdir fileThree.txt myFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
rm command to delete a file | rm |
| 10 | asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text finalDestination.txt source.txt fileThree.text lynxCommands.docx yourdir fileThree.txt myFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % rm yourdir rm: yourdir: is a directory asismisr@CTIPL-MAC-348 lynxPlayground % rm -r yourdir asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text finalDestination.txt source.txt fileThree.text lynxCommands.docx fileThree.txt myFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
using rm command to remove a directory. - rm yourdir: will not allow you to delete a directory unless its empty. - '-r' in rm -r yourdir : This flag stands for "recursive." It tells rm to remove the directory and all of its contents, including any subdirectories and files within it. |
rm |
| 11 | asismisr@CTIPL-MAC-348 lynxPlayground % mkdir testdir1 testdir2 testdir3 asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text lynxCommands.docx testdir2 fileThree.text myFile.txt testdir3 fileThree.txt source.txt finalDestination.txt testdir1 asismisr@CTIPL-MAC-348 lynxPlayground % |
using mkdir to create multiple directories | mkdir |
| 12 | asismisr@CTIPL-MAC-348 lynxPlayground % mkdir -p world/countries/state asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text lynxCommands.docx testdir2 fileThree.text myFile.txt testdir3 fileThree.txt source.txt world finalDestination.txt testdir1 asismisr@CTIPL-MAC-348 lynxPlayground % ls world countries asismisr@CTIPL-MAC-348 lynxPlayground % ls world/countries state asismisr@CTIPL-MAC-348 lynxPlayground % |
using mkdir to create multiple nested directories. - '-p': This option stands for "parents." It tells mkdir to create the parent directories if they do not already exist. |
mkdir |
| 13 | asismisr@CTIPL-MAC-348 lynxPlayground % cd world asismisr@CTIPL-MAC-348 world % cd countries asismisr@CTIPL-MAC-348 countries % pwd /Users/asismisr/lynxPlayground/world/countries asismisr@CTIPL-MAC-348 countries % cd ~ asismisr@CTIPL-MAC-348 ~ % pwd /Users/asismisr asismisr@CTIPL-MAC-348 ~ % |
using cd ~ command to go to Home directory | cd |
| 14 | asismisr@CTIPL-MAC-348 ~ % pwd /Users/asismisr asismisr@CTIPL-MAC-348 ~ % cd lynxPlayground asismisr@CTIPL-MAC-348 lynxPlayground % pwd /Users/asismisr/lynxPlayground |
using cd command to change directory | cd |
| 15 | asismisr@CTIPL-MAC-348 lynxPlayground % pwd /Users/asismisr/lynxPlayground asismisr@CTIPL-MAC-348 lynxPlayground % cd .. asismisr@CTIPL-MAC-348 ~ % pwd /Users/asismisr asismisr@CTIPL-MAC-348 ~ % |
using cd .. to go to parent directory | cd |
| 16 | asismisr@CTIPL-MAC-348 lynxPlayground % cd world asismisr@CTIPL-MAC-348 world % ls countries asismisr@CTIPL-MAC-348 world % rmdir countries rmdir: countries: Directory not empty |
using rmdir to remove a directory, in this case rmdir command will fail since we have nested folders here. - use rm -r countries to remove it alsong with all the nested directories |
rmdir |
| 17 | asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text lynxCommands.docx testdir2 fileThree.text myFile.txt testdir3 fileThree.txt source.txt world finalDestination.txt testdir1 asismisr@CTIPL-MAC-348 lynxPlayground % rmdir testdir1 testdir2 testdir3 asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text finalDestination.txt source.txt fileThree.text lynxCommands.docx world fileThree.txt myFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
using rmdir to delete multiple directories | rmdir |
| 18 | asismisr@CTIPL-MAC-348 ~ % ls AppData Karate-Automation TaxAutomation Applications Library cmsApiAutomation CmsAutomation Movies lynxPlayground Desktop Music runnerUiMainBranch Documents Pictures ~zshrc Downloads Postman IdeaProjects Public asismisr@CTIPL-MAC-348 ~ % ls -a . .zprofile .-CheckPointSecuredDirectoryDon'tRemove .zsh_history .. .zsh_sessions .CFUserTextEncoding .zshrc .DS_Store AppData .Trash Applications .android CmsAutomation .azure Desktop .config Documents .gitconfig Downloads .gradle IdeaProjects .hawtjni Karate-Automation .k8slens Library .karate Movies .kube Music .lesshst Pictures .local Postman .m2 Public .mysql_history TaxAutomation .offsetexplorer3 cmsApiAutomation .putty lynxPlayground .rp runnerUiMainBranch .viminfo ~zshrc asismisr@CTIPL-MAC-348 ~ % |
by using ls command we can display all the visible files. - ls -a : will display all the hidden files |
ls |
| 19 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -a . fileOne.text lynxCommands.docx world .. fileThree.text myFile.txt .DS_Store fileThree.txt source.txt .hiddenTouchFile.txt finalDestination.txt touchFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls -l total 48 -rw-r--r--@ 1 asismisr staff 51 Aug 9 08:34 fileOne.text -rw-r--r--@ 1 asismisr staff 23 Aug 9 08:44 fileThree.text -rw-r--r--@ 1 asismisr staff 19 Aug 9 08:18 fileThree.txt -rw-r--r--@ 1 asismisr staff 23 Aug 9 08:40 finalDestination.txt -rw-r--r--@ 1 asismisr staff 0 Aug 9 08:04 lynxCommands.docx -rw-r--r--@ 1 asismisr staff 53 Aug 9 08:10 myFile.txt -rw-r--r--@ 1 asismisr staff 23 Aug 9 08:40 source.txt -rw-r--r-- 1 asismisr staff 0 Aug 11 13:36 touchFile.txt drwxr-xr-x 3 asismisr staff 96 Aug 11 13:20 world asismisr@CTIPL-MAC-348 lynxPlayground % |
using ls -l we can display other info like: File Permissions, Number of Links, Owner, Group, File Size, Modification Date and Time, File Name | ls |
| 20 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -F fileOne.text finalDestination.txt source.txt fileThree.text lynxCommands.docx touchFile.txt fileThree.txt myFile.txt world/ asismisr@CTIPL-MAC-348 lynxPlayground % |
ls -F will add / at the end of a directory | ls |
| 21 | asismisr@CTIPL-MAC-348 lynxPlayground % touch touchFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls fileOne.text finalDestination.txt source.txt fileThree.text lynxCommands.docx touchFile.txt fileThree.txt myFile.txt world asismisr@CTIPL-MAC-348 lynxPlayground % |
using touch command to create files | touch |
| 22 | asismisr@CTIPL-MAC-348 lynxPlayground % touch .hiddenTouchFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls -a . fileOne.text lynxCommands.docx world .. fileThree.text myFile.txt .DS_Store fileThree.txt source.txt .hiddenTouchFile.txt finalDestination.txt touchFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
using touch command to create hidden files. - using '.' before file name will make it hidden |
touch |
| 23 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -R fileOne.text finalDestination.txt source.txt fileThree.text lynxCommands.docx touchFile.txt fileThree.txt myFile.txt world ./world: countries ./world/countries: state ./world/countries/state: asismisr@CTIPL-MAC-348 lynxPlayground % |
ls -R will display the list with all the sub directories | ls |
| 24 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -lS total 48 drwxr-xr-x 3 asismisr staff 96 Aug 11 13:20 world -rw-r--r--@ 1 asismisr staff 53 Aug 9 08:10 myFile.txt -rw-r--r--@ 1 asismisr staff 51 Aug 9 08:34 fileOne.text -rw-r--r--@ 1 asismisr staff 23 Aug 9 08:44 fileThree.text -rw-r--r--@ 1 asismisr staff 23 Aug 9 08:40 finalDestination.txt -rw-r--r--@ 1 asismisr staff 23 Aug 9 08:40 source.txt -rw-r--r--@ 1 asismisr staff 19 Aug 9 08:18 fileThree.txt -rw-r--r--@ 1 asismisr staff 0 Aug 9 08:04 lynxCommands.docx -rw-r--r-- 1 asismisr staff 0 Aug 11 13:36 touchFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
ls -lS will display the order of the file in Descending order based on the file size. | ls |
| 25 | asismisr@CTIPL-MAC-348 lynxPlayground % ls a.txt fileThree.text lynxCommands.docx touchFile.txt b.docx fileThree.txt myFile.txt world fileOne.text finalDestination.txt source.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls ?.* a.txt b.docx asismisr@CTIPL-MAC-348 lynxPlayground % |
here ls command is used to display the file name having only 1 character and any extension. - '?' : here represents only 1 character. |
ls |
| 26 | asismisr@CTIPL-MAC-348 lynxPlayground % ls a.txt fileThree.text lynxCommands.docx touchFile.txt b.docx fileThree.txt myFile.txt world fileOne.text finalDestination.txt source.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls file*.text fileOne.text fileThree.text asismisr@CTIPL-MAC-348 lynxPlayground % |
here, * represents any character | ls |
| 27 | asismisr@CTIPL-MAC-348 lynxPlayground % ls a.txt fileThree.text lynxCommands.docx touchFile.txt b.docx fileThree.txt myFile.txt world fileOne.text finalDestination.txt source.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls [a-z]*.txt a.txt finalDestination.txt source.txt fileThree.txt myFile.txt touchFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
here [a-z] represnts range of character. | ls |
| 28 | head -20 myFile.txt | here Head command will display the top 20 lines form the file | head |
| 29 | tail -20 myFile.txt | here tail command will display the last 20 lines form the file | tail |
| 30 | more myFile.txt | here more command will display the content page by page | more |
| 31 | asismisr@CTIPL-MAC-348 ~ % who Ashish.Mishra@dpworld.com console Aug 5 12:08 asismisr ttys000 Aug 11 13:00 asismisr@CTIPL-MAC-348 ~ % |
who command in Unix-like operating systems (such as Linux and macOS) is used to display information about users who are currently logged into the system. 1. Username: Ashish.Mishra@dpworld.com: The full email format indicates the user Ashish.Mishra is logged in. asismisr: This is another user (or possibly the same user under a different session) logged in with the username asismisr. 2.Terminal or Line: console: This indicates the session is directly on the system console (likely the main graphical login session). ttys000: This is a terminal session, often associated with a virtual terminal or an SSH session. 3.Login Date and Time: Aug 5 12:08: The user Ashish.Mishra logged in on August 5th at 12:08 PM. Aug 11 13:00: The user asismisr logged in on August 11th at 1:00 PM. |
who |
| 32 | asismisr@CTIPL-MAC-348 ~ % who Ashish.Mishra@dpworld.com console Aug 5 12:08 asismisr ttys000 Aug 11 13:00 asismisr@CTIPL-MAC-348 ~ % whoami asismisr asismisr@CTIPL-MAC-348 ~ % |
whoami will display the user name of the current user | whoami |
| 33 | asismisr@CTIPL-MAC-348 ~ % hostname CTIPL-MAC-348.local asismisr@CTIPL-MAC-348 ~ % |
hostname will display the hostname of the unix | hostname |
| 34 | asismisr@CTIPL-MAC-348 ~ % uptime 15:41 up 6 days, 3:37, 2 users, load averages: 2.19 2.13 9.65 asismisr@CTIPL-MAC-348 ~ % |
uptime command in Unix-like operating systems provides a summary of how long the system has been running, how many users are currently logged in, and the system's load averages. Current Time: 15:41: The current time is 3:41 PM. System Uptime: up 6 days, 3:37: The system has been running continuously for 6 days and 3 hours 37 minutes. Number of Users: 2 users: There are currently 2 users logged into the system. Load Averages: load averages: 2.19 2.13 9.65: These are the system's load averages over the last 1, 5, and 15 minutes, respectively. |
uptime |
| 35 | asismisr@CTIPL-MAC-348 ~ % cal | the cal command will show the calendar for the current month | cal |
| 36 | asismisr@CTIPL-MAC-348 ~ % cal 2024 | displays the calendar for specific year | cal |
| 37 | asismisr@CTIPL-MAC-348 ~ % cal 8 2024 | displays the calendar month 8 of year 2024 | cal |
| 38 | asismisr@CTIPL-MAC-348 ~ % cal -y | displays the calendar of the current year | cal |
| 39 | asismisr@CTIPL-MAC-348 ~ % date Sun Aug 11 15:51:15 IST 2024 |
displays the current date and time | date |
| 40 | asismisr@CTIPL-MAC-348 ~ % date "+%Y" 2024 |
date command to display the current year | date |
| 41 | asismisr@CTIPL-MAC-348 ~ % date "+%m" 08 |
date command to display the current Month in number | date |
| 42 | asismisr@CTIPL-MAC-348 ~ % date "+%d-%m-%Y" 11-08-2024 |
date formatting to display the entire date | date |
| 43 | asismisr@CTIPL-MAC-348 ~ % date "+%a" Sun asismisr@CTIPL-MAC-348 ~ % date "+%A" Sunday |
to display week day | date |
| 44 | asismisr@CTIPL-MAC-348 ~ % date "+%b" Aug asismisr@CTIPL-MAC-348 ~ % date "+%B" August |
date command to display the current Month in alphabet | date |
| 45 | asismisr@CTIPL-MAC-348 ~ % date "+%H" 15 asismisr@CTIPL-MAC-348 ~ % date "+%I" 03 |
date command to display the current time in hour - %H will display in 24hrs - %I will display in 12hrs |
date |
| 46 | asismisr@CTIPL-MAC-348 ~ % date "+%H:%M:%S" 16:00:39 asismisr@CTIPL-MAC-348 ~ % date "+%I:%M:%S" 04:02:32 |
date formatting to display the time | date |
| 47 | asismisr@CTIPL-MAC-348 ~ % date "+today's date and time is %d-%B-%Y %H:%m:%S" today's date and time is 11-August-2024 16:08:58 |
date formatting to display the date and time together | date |
| 48 | wc fileName O/P: 12 56 345 fileName |
The wc command in Unix/Linux is used to count the number of lines, words, and characters in a file. Here's what the numbers represent: 12: The number of lines in file1. 56: The number of words in file1. 345: The number of bytes in file1. You can also use specific options with wc: wc -l file1 to count the lines only. wc -w file1 to count the words only. wc -c file1 to count the bytes (or characters) only. |
wc |
| 49 | sort file1 | The sort command in Unix/Linux is used to sort the lines of text files. When you run sort file1, it sorts the lines in file1 in alphabetical order by default and prints the sorted output to the terminal. Common Options with sort: sort -r file1: Sorts the lines in reverse (descending) order. sort -n file1: Sorts lines as numbers (useful if the file contains numeric data). sort -u file1: Removes duplicate lines and sorts the result. sort -o output.txt file1: Writes the sorted output directly to output.txt. |
sort |
| 50 | sort file1.txt >file2.txt | sort the file data of file1.txt and put it into file2.txt | sort |
| 51 | uniq file1.txt | The uniq command in Unix/Linux is used to report or filter out repeated lines in a file. If you want to remove duplicate lines and get unique lines from file1.txt | uniq |
| 52 | uniq file1.txt > unique_file1.txt | This command will save the unique lines from file1.txt into unique_file1.txt. | uniq |
| 53 | uniq -d file1.txt | print only the duplicate line | uniq |
| 54 | uniq -u file1.txt | print only the unique line which appear only once | uniq |
| 55 | cmp file1 file2 | The cmp command is used to compare two files byte by byte. | cmp |
| 56 | diff -u file1 file2 | The diff command is used to compare the contents of two files and show the differences between them | diff |
| 57 | sort file1 -o file1_sorted sort file2 -o file2_sorted comm file1_sorted file2_sorted |
The comm command is used to compare two sorted files line by line and output the lines that are unique to each file and the lines that are common to both. Note: Ensure the files are sorted This will output three columns: Lines only in file1_sorted Lines only in file2_sorted Lines common to both files |
comm |
| 58 | Redirection are of 3 types: 1. Error redirection : is denoted by > or >> or 2, it redirects the error to some other file 2. output redirection : is denoted by > or >> or 1, it redirects the output to some other file 3. Input redirection : is denoted by < or 0, it redirects the input from some other file > : will replace the old content of the file >> : will append over the old content - Whenever a program is executed at the terminal, 3 files are generated: standard input(0), standard output(1), standard error(2). These files are always created whenever a program is run. By default, an error stream is displayed on the screen. - Always use number (2) in case of error redirection. - in case of Input & output redirection the numbers are optional |
redirection | |
| 59 | asismisr@CTIPL-MAC-348 lynxPlayground % pwd /Users/asismisr/lynxPlayground asismisr@CTIPL-MAC-348 lynxPlayground % pwd > pwd.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls a.txt fileThree.txt pwd.txt b.docx finalDestination.txt source.txt fileOne.text lynxCommands.docx touchFile.txt fileThree.text myFile.txt world asismisr@CTIPL-MAC-348 lynxPlayground % cat pwd.txt /Users/asismisr/lynxPlayground asismisr@CTIPL-MAC-348 lynxPlayground % |
Output redirection: read input from keyboard and store the output in output.txt file (1st solution) - note here the when pwd was used with redirection no output was generated in console. |
redirection |
| 60 | asismisr@CTIPL-MAC-348 lynxPlayground % pwd /Users/asismisr/lynxPlayground asismisr@CTIPL-MAC-348 lynxPlayground % pwd 1> pwd.txt asismisr@CTIPL-MAC-348 lynxPlayground % cat pwd.txt /Users/asismisr/lynxPlayground asismisr@CTIPL-MAC-348 lynxPlayground % |
Output redirection: read input from keyboard and store the output in output.txt file (2nd solution) - note here the when pwd was used with redirection no output was generated in console. |
redirection |
| 61 | asismisr@CTIPL-MAC-348 lynxPlayground % rm noSuchFile.txt rm: noSuchFile.txt: No such file or directory asismisr@CTIPL-MAC-348 lynxPlayground % rm noSuchFile.txt 2> errorLog.txt asismisr@CTIPL-MAC-348 lynxPlayground % cat errorLog.txt rm: noSuchFile.txt: No such file or directory asismisr@CTIPL-MAC-348 lynxPlayground % |
Error redirection: read input from keyboard and store the error in errorLog.txt file - note here use 2 to explicitly mention it as an standard error log, if not used the error will be displaced in the terminal since it will consider it as an output redirection |
redirection |
| 62 | asismisr@CTIPL-MAC-348 lynxPlayground % rm noSuchFile.txt > output.txt 2>errorLog.txt | Output redirection & Error redirection Combined - Over here if the the output will go to output.txt file and error message will got to errorLog.txt file |
redirection |
| 63 | asismisr@CTIPL-MAC-348 lynxPlayground % cat > inputfile.txt my file data ^C asismisr@CTIPL-MAC-348 lynxPlayground % cat 0< inputfile.txt my file data asismisr@CTIPL-MAC-348 lynxPlayground % |
Input redirection: - read the input/command from input.txt file and display the output in terminal. |
redirection |
| 64 | asismisr@CTIPL-MAC-348 lynxPlayground % cat 0< inputfile.txt 1> outputfile.txt asismisr@CTIPL-MAC-348 lynxPlayground % cat outputfile.txt my file data asismisr@CTIPL-MAC-348 lynxPlayground % |
Input & Output redirection combined: - read the input/command from input.txt file and Store the output in outfile.txt. |
redirection |
| 65 | asismisr@CTIPL-MAC-348 lynxPlayground % tty /dev/ttys000 asismisr@CTIPL-MAC-348 lynxPlayground % pwd >/dev/ttys001 asismisr@CTIPL-MAC-348 lynxPlayground % echo "hello" 1> /dev/ttys001 |
write the command in terminal one and print the out put in second terminal, pwd and echo will be displayed in second terminal for which tty value would be '/dev/ttys001' - Every terminal is a file and to know its location use command 'tty'. |
redirection |
| 66 | asismisr@CTIPL-MAC-348 lynxPlayground % tty /dev/ttys000 |
- Every terminal is a file and to know its location use command 'tty'. |
tty |
| 67 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -l | head -5 total 72 -rw-r--r-- 1 asismisr staff 0 Aug 11 15:03 a.txt -rw-r--r-- 1 asismisr staff 0 Aug 11 15:03 b.docx -rw-r--r--@ 1 asismisr staff 46 Aug 22 19:58 errorLog.txt -rw-r--r--@ 1 asismisr staff 51 Aug 9 08:34 fileOne.text |
A pipe is a form of redirection (transfer of standard output to some other destination) that is used in Linux and other Unix-like operating systems to send the output of one command/program/process to another command/program/process for further processing. The Unix/Linux systems allow the stdout of a command to be connected to the stdin of another command. You can make it do so by using the pipe character ‘|’. The pipe is used to combine two or more commands, and in this, the output of one command acts as input to another command, and this command’s output may act as input to the next command, and so on. It can also be visualized as a temporary connection between two or more commands/ programs/ processes. The command line programs that do the further processing are referred to as filters. Pipes are unidirectional i.e., data flows from left to right through the pipeline. |
piping |
| 68 | Tee reads the standard input and writes it to both the standard output and one or more files. The command is named after the T-splitter used in plumbing. It basically breaks the output of a program so that it can be both displayed and saved in a file. It does both the tasks simultaneously, copies the result into the specified files or variables and also display the result. | tee | |
| 69 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -l | tee allFiles.txt | wc -l 16 asismisr@CTIPL-MAC-348 lynxPlayground % cat allFiles.txt | wc -l 16 |
write a command to 'save the ls command in an output file and that should be provided as an input to the wc command ' | tee |
| 70 | xargs is a Unix command which can be used to build and execute commands from standard input. Xargs is a great command that reads streams of data from standard input, then generates and executes command lines; meaning it can take output of a command and passes it as argument of another command. If no command is specified, xargs executes echo by default. You many also instruct it to read data from a file instead of stdin. |
xargs | |
| 71 | asismisr@CTIPL-MAC-348 lynxPlayground % cat iterativedeletion.txt test1 test2 test3 test4 asismisr@CTIPL-MAC-348 lynxPlayground % cat iterativedeletion.txt | xargs rm asismisr@CTIPL-MAC-348 lynxPlayground % ls a.txt fileThree.txt output.txt allFiles.txt finalDestination.txt outputfile.txt b.docx inputfile.txt source.txt errorLog.txt iterativedeletion.txt touchFile.txt fileOne.text lynxCommands.docx world fileThree.text myFile.txt asismisr@CTIPL-MAC-348 lynxPlayground % |
iterativedeletion.txt contains the name of files, and we have to delete those files whose name are available in iterativedeletion.txt | xargs |
| 72 | asismisr@CTIPL-MAC-348 lynxPlayground % date | xargs echo Sun Aug 25 16:07:47 IST 2024 |
Display the output of date command using echo command | xargs |
| 73 | The following are some basic regular expressions: Sr. Symbol Description 1. . It is called a wild card character, It matches any one character other than the new line. 2. ^ It matches the start of the string. 3. $ It matches the end of the string. 4. * It matches up to zero or more occurrences i.e. any number of times of the character of the string. 5. \ It is used for escape following character. 6. () It is used to match or search for a set of regular expressions. 7. ? It matches exactly one character in the string or stream. Below is the link to the text file that we are going to use: |
regRex | |
| 74 | asismisr@CTIPL-MAC-348 lynxPlayground % ls *.txt a.txt finalDestination.txt output.txt allFiles.txt inputfile.txt outputfile.txt errorLog.txt iterativedeletion.txt source.txt fileThree.txt myFile.txt touchFile.txt |
- list out all the files with .txt extension | regRex |
| 75 | asismisr@CTIPL-MAC-348 lynxPlayground % ls ??.* on.txt se.txt |
- list out the files having only 2 characters - a single '?' represents only 1 character |
regRex |
| 76 | asismisr@CTIPL-MAC-348 lynxPlayground % ls ???*.* allFiles.txt finalDestination.txt output.txt errorLog.txt inputfile.txt outputfile.txt fileOne.text iterativedeletion.txt source.txt fileThree.text lynxCommands.docx touchFile.txt fileThree.txt myFile.txt |
- list the file having only 3 characters | regRex |
| 77 | asismisr@CTIPL-MAC-348 lynxPlayground % ls [fil]* fileOne.text finalDestination.txt lynxCommands.docx fileThree.text inputfile.txt fileThree.txt iterativedeletion.txt |
- list all the files whose name starts with 'f', 'i', 'l' | regRex |
| 78 | asismisr@CTIPL-MAC-348 lynxPlayground % ls [\!fil]* a.txt errorLog.txt output.txt source.txt allFiles.txt myFile.txt outputfile.txt touchFile.txt b.docx on.txt se.txt world: countries |
- list all the files whose name should not starts with 'f', 'i', 'l' | regRex |
| 79 | asismisr@CTIPL-MAC-348 lynxPlayground % ls [a-z]* a.txt fileThree.txt on.txt allFiles.txt finalDestination.txt output.txt b.docx inputfile.txt outputfile.txt errorLog.txt iterativedeletion.txt se.txt fileOne.text lynxCommands.docx source.txt fileThree.text myFile.txt touchFile.txt world: countries |
- list out the file name starts with [a to z] | regRex |
| 80 | ls [a-z][0-9][A-Z]* | - list out the file name which start with 1st character a lower case character, 2nd charcter as 0-9, 3rd chacter as A-Z | regRex |
| 81 | ls {*.java , *.py} | - list out all the file having .java or .py extension | regRex |
| 82 | The grep command will get the entire line having that string to be searched Options Available in grep Command Options Description -c This prints only a count of the lines that match a pattern -h Display the matched lines, but do not display the filenames. –i Ignores, case for matching -l Displays list of a filenames only. -n Display the matched lines and their line numbers. -v This prints out all the lines that do not matches the pattern -e exp Specifies expression with this option. Can use multiple times. -f file Takes patterns from file, one per line. -E Treats pattern as an extended regular expression (ERE) -w Match whole word -o Print only the matched parts of a matching line, with each such part on a separate output line. -A n Prints searched line and nlines after the result. -B n Prints searched line and n line before the result. -C n Prints searched line and n lines after before the result. |
grep | |
| 83 | asismisr@CTIPL-MAC-348 lynxPlayground % cat logfile.txt My name is Ashish. My name is Aditya. My name is Mushes. My name is Akhilesh. My name is Aamir. My name is Ashish. My name is Rock.% asismisr@CTIPL-MAC-348 lynxPlayground % grep "Ashish" logfile.txt My name is Ashish. My name is Ashish. |
The grep command will get the entire line having that string to be searched | grep |
| 84 | asismisr@CTIPL-MAC-348 lynxPlayground % grep -i "aSHisH" logfile.txt My name is Ashish. My name is Ashish. |
–i Ignores, case for matching | grep |
| 85 | asismisr@CTIPL-MAC-348 lynxPlayground % grep -n "Ashish" logfile.txt 1:My name is Ashish. 6:My name is Ashish. |
-n Display the matched lines and their line numbers. | grep |
| 86 | asismisr@CTIPL-MAC-348 lynxPlayground % grep -c "Ashish" logfile.txt 2 |
-c This prints only a count of the lines that match a pattern |
grep |
| 87 | asismisr@CTIPL-MAC-348 lynxPlayground % grep -v "Ashish" logfile.txt My name is Aditya. My name is Mushes. My name is Akhilesh. My name is Aamir. My name is Rock. |
-v This prints out all the lines that do not matches the pattern |
grep |
| 88 | grep -l "Ashish" file1 file2 | this will show the string found in which which file -l Displays list of a filenames only. |
grep |
| 89 | grep "^D" Logfile.txt | Display all the lines that starts with 'D' | grep |
| 90 | grep "i$" Logfile.txt | Display all the lines that ends with 'i' | grep |
| 91 | grep '[ABCD]' logfile.txt | Display all the lines that contains any of the given characters (A,B,C,D) | grep |
| 92 | grep '[^ABCD]' logfile.txt | Display all the lines that Does not contains any of the given characters (A,B,C,D) | grep |
| 93 | asismisr@CTIPL-MAC-348 lynxPlayground % cat logfile.txt My name is Ashish. My name is Aditya. My name is Mushes. My name is Akhilesh. My name is Aamir. My name is Ashish. My name is Rock.% asismisr@CTIPL-MAC-348 lynxPlayground % grep -e "Ashish" -e "Rock" logfile.txt My name is Ashish. My name is Ashish. My name is Rock. |
using -e to search mutiple strings in a file | grep |
| 94 | asismisr@CTIPL-MAC-348 lynxPlayground % egrep "(Ashish|Rock)" logfile.txt My name is Ashish. My name is Ashish. My name is Rock. |
using egrep to search mutiple strings in a file | egrep |
| 95 | In Unix operating systems, the chmod command is used to change the access mode of a file. The name is an abbreviation of change mode. Which states that every file and directory has a set of permissions that control the permissions like who can read, write or execute the file. In this the permissions have three categories: read, write, and execute simultaneously represented by `r`, `w` and `x`. These letters combine together to form a specific permission for a group of users. Options Available in chmod Command Linux Options Description `-R` Apply the permission change recursively to all the files and directories within the specified directory. `-v` It will display a message for each file that is processed. while indicating the permission change that was made. `-c` It works same as `-v` but in this case it only displays messages for files whose permission is changed. `-f` It helps in avoiding display of error messages. `-h` Change the permissions of symbolic links instead of the files they point to. 1) Symbolic mode If we talk about symbolic mode, we can say that it is the most common method used for specifying fir permissions. In this we have to make a combination of letters and operators to set or tell what to do with permissions. The following operators can be used with the symbolic mode: Operators Definition `+` Add permissions `-` Remove permissions `=` Set the permissions to the specified values The following letters that can be used in symbolic mode: Letters Definition `r` Read permission `w` Write permission `x` Execute permission The following Reference that are used: Reference Class u Owner g Group o Others a All (owner,groups,others) 2) Octal mode It is also a method for specifying permissions. In this method we specify permission using three-digit number. Where.. First digit specify the permission for Owner. Second digit specify the permission for Group. Third digit specify the permission for Others. The digits NOTE: The digits are calculated by adding the values of the individual permissions. Value Permission 4 Read Permission 2 Write Permission 1 Execute Permission |
chmod | |
| 96 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -l allFiles.txt -rw-r--r--@ 1 asismisr staff 903 Aug 25 15:47 allFiles.txt asismisr@CTIPL-MAC-348 lynxPlayground % chmod u+x allFiles.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls -l allFiles.txt -rwxr--r--@ 1 asismisr staff 903 Aug 25 15:47 allFiles.txt |
write a command to add execute permission to the owner of the file Note: rwx: represents Owner is having read, write, execute permission. (middle)r--: represents group having read permission. (last)r--: represents others having read permission. |
chmod |
| 97 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -l allFiles.txt -rw-r--r--@ 1 asismisr staff 903 Aug 25 15:47 allFiles.txt asismisr@CTIPL-MAC-348 lynxPlayground % chmod u+x,g+rw,o+rw allFiles.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls -l allFiles.txt -rwxrw-rw-@ 1 asismisr staff 903 Aug 25 15:47 allFiles.txt |
write a command to add execute permission to the owner of the file and add read, write permission to group and others | chmod |
| 98 | asismisr@CTIPL-MAC-348 lynxPlayground % ls -l allFiles.txt -rwxrw-rw-@ 1 asismisr staff 903 Aug 25 15:47 allFiles.txt asismisr@CTIPL-MAC-348 lynxPlayground % chmod g-r,o-r allFiles.txt asismisr@CTIPL-MAC-348 lynxPlayground % ls -l allFiles.txt -rwx-w--w-@ 1 asismisr staff 903 Aug 25 15:47 allFiles.txt |
write a command to remove read permission from group and others | chmod |
| 99 | Process are of 2 types: - foreground - background (we can trigger the back ground command by putting & after the command ) |
ps | |
| 100 | asismisr@CTIPL-MAC-348 lynxPlayground % ps -f UID PID PPID C STIME TTY TIME CMD 502 52088 52082 0 10:05PM ttys000 0:00.20 -zsh 502 53052 52088 0 10:24PM ttys000 0:00.01 sh shellScript.sh 502 53053 53052 0 10:24PM ttys000 0:00.01 sleep 100 502 53055 52088 0 10:24PM ttys000 0:00.01 sh shellScript.sh 502 53056 53055 0 10:24PM ttys000 0:00.00 sleep 100 502 53061 52088 0 10:24PM ttys000 0:00.02 sh shellScript.sh 502 53062 53061 0 10:24PM ttys000 0:00.00 sleep 100 |
ps command will show the processes running. -f meaning the processes running by the user. - Pid(parent id) and PPid(parent process id) : there are some process which are having a prarent and child relation, if suppose PPID of one of the process matches with the PID of any other process then it means it is its parent process |
ps |
| 101 | asismisr@CTIPL-MAC-348 lynxPlayground % ps -e PID TTY TIME CMD 1 ?? 278:41.19 /sbin/launchd 509 ?? 0:56.78 /System/Library/PrivateFrameworks/CoreParsec.framework/parsecd 1108 ?? 99:11.12 /usr/libexec/logd 1110 ?? 6:25.55 /usr/libexec/UserEventAgent (System) 1112 ?? 0:35.56 /System/Library/PrivateFrameworks/Uninstall.framework/Resources/uninstalld 1113 ?? 45:05.89 /System/Library/Frameworks/CoreServices.framework/Versions/A/Frameworks/FSEvents.framework/Versi 1114 ?? 9:06.77 /System/Library/PrivateFrameworks/MediaRemote.framework/Support/mediaremoted 1117 ?? 4:15.37 /usr/sbin/systemstats --daemon 1120 ?? 23:34.48 /usr/libexec/configd 1122 ?? 14:16.66 /System/Library/CoreServices/powerd.bundle/powerd 1123 ?? 0:12.83 /usr/libexec/IOMFB_bics_daemon |
ps command will show the processes running. -e meaning the processes running by the machine. |
ps |
| 102 | asismisr@CTIPL-MAC-348 lynxPlayground % ps 1108 PID TT STAT TIME COMMAND 1108 ?? Ss 99:11.55 /usr/libexec/logd |
this ps command along with PID, will display the process info | ps |
| 103 | ps -h | will dsplay th process with Pid(parent id) and PPid(parent process id) structure | ps |
| 104 | asismisr@CTIPL-MAC-348 lynxPlayground % ps -f UID PID PPID C STIME TTY TIME CMD 502 52088 52082 0 10:05PM ttys000 0:00.22 -zsh 502 53147 52088 0 10:27PM ttys000 0:00.01 sh shellScript.sh 502 53148 53147 0 10:27PM ttys000 0:00.01 sleep 100 asismisr@CTIPL-MAC-348 lynxPlayground % kill 53148 asismisr@CTIPL-MAC-348 lynxPlayground % shellScript.sh: line 3: 53148 Terminated: 15 sleep 100 [1] + done sh shellScript.sh asismisr@CTIPL-MAC-348 lynxPlayground % ps -f UID PID PPID C STIME TTY TIME CMD 502 52088 52082 0 10:05PM ttys000 0:00.23 -zsh asismisr@CTIPL-MAC-348 lynxPlayground % |
the kill command will kill the process corresponding to the PID | kill |
| 105 | asismisr@CTIPL-MAC-348 lynxPlayground % ps -f UID PID PPID C STIME TTY TIME CMD 502 52088 52082 0 10:05PM ttys000 0:00.24 -zsh 502 53259 52088 0 10:29PM ttys000 0:00.01 sh shellScript.sh 502 53260 53259 0 10:29PM ttys000 0:00.00 sleep 100 asismisr@CTIPL-MAC-348 lynxPlayground % kill -9 53259 53260 [1] + killed sh shellScript.sh asismisr@CTIPL-MAC-348 lynxPlayground % ps -f UID PID PPID C STIME TTY TIME CMD 502 52088 52082 0 10:05PM ttys000 0:00.25 -zsh |
kill command to kill mutiple process in one go | kill |
| 106 | nano filename.txt | nano command can be used to open the editor to edit file content | nano |
| 107 | vim filename.txt | vim command can be used to open the editor to edit file content | vim |
| 108 | gedit filename.txt | gedit command can be used to open the editor to edit file content | gedit |
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