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Command to know the version of UNIX/LINUX installed
uname –a
Command to know Home directory of User
echo $HOME
- cd .
- Current Directory
- cd ..
- Parent Directory
- cd
- Home Directory
- cd –
- to go back to previous directory
- pwd
- Present working directory
- cd $HOME
- will go to home directory
- cd
- will go to root directory
- cd $HOME
- will go to home directory
Listing Command
ls : list down the files in current directory
File Command
Creation of File
vi <File_Name_To Create>
Note: It will open VI editor to write the content in File.
OR
Touch <File_Name_To_Create>
Note*: It will only create the file with given name if it doesn’t exist.
Editing the File
vi <File_Name_To Edit>
- Enter into input mode – i (Click small I)
- Save the content and exit – :wq (! Can be used to force the exit)
- Exit the file without saving it – :q (! Can be used to force the exit)
View the Content of File
Read only View can be done using cat command.
cat <File_Name_To_View>
Note*: It will display the content and return to command prompt.
Remove the File
rm <File_Name_To_Remove>
Change File Permission
chmod <Numeric Value of File Permission> <File_Name_To_Change_Mode>
Attribute
Readable : 4
Not Readable : 0
Writable : 2
Not Writtable : 0
Executable : 1
Not Executable : 0
Every file or directory has 3 type of permission.
- Owner Permission (Read,Write,Execute)
- Group Permission (Read,Write,Execute)
- Public Permission (Read,Write,Execute)
So the final permission of a file will look like this XXXXXXXXX (Owner – Group - Public).
How to calculate Numeric Value of File Permission
Numeric value is file permission would be of length 3. First number will represent the permission of Owner, second is for Group and third is for public permission.
Now we will calculate permission for different category individually and then we will add it to get final permission.
Owner Permission
As given above look for the permission an owner has and then integer value of it to get the final number.
Readable + Writable + Executable = 4+2+1 = 7
Subtract the corresponding number if permission is not allowed for given action. Like no readable permission is there than final value would be 7-4= 3
Group Permission
As given above look for the permission a group has and then integer value of it to get the final number.
Readable + Writable + Executable = 4+2+1 = 7
Subtract the corresponding number if permission is not allowed for given action. Like no readable permission is there than final value would be 7-4= 3
Public Permission
As given above look for the permission public has and then integer value of it to get the final number.
Readable + Writable + Executable = 4+2+1 = 7
Subtract the corresponding number if permission is not allowed for given action. Like no readable permission is there than final value would be 7-4= 3
In the end we will add all 3 numbers obtained through above process. So if all category only has read property then Permission would be “333”.
If all permission is there then permission would be “777”.
Search File
File searching can be done using find command.
To search a file in current directory only (Not in subdirectory)
To search a file in current directory and subdirectory
find . -name MFSB*.pc
Search a term in Files
To search a term in files grep command can be used.
Look for word JBT in all file in current directory only.
grep -il “JBT” *
i–ignore case
l–file name (only)
n–line no’s
c–No of occurrence of a word
find . -name MFSB*.pc
find . -name–command
Other Commands
Clear Console : clear
Previous command fired in same session : Esc + k
Current logged in user : whoami
All running processes : ps -ef
All logged in user : who
Remove all content of a file (Empty File) : > file_name
Display the list of Command Fired in Current Session
history // will display the last 10 commands fired
history 100 // will display the last 100 command fired
Alias Creation
In order to create ALIAS you need to make an entry in “.profile” file in user home directory.
alias — needs to be added in .profile in $HOME path
How to create Alias
Step 1: Look for the home directory of current user (Use Command “echo $HOME”).
Step 2: Switch to home directory (Use Command “cd $HOME”).
Step 3: Open “.profile” file (Use Command “vi .profile”).
Step 4: Enter the line “ alias jbt=”echo Hello JBT” ”
Step 5: Save and exit file. (Use Command Esc+:+wq)
Step 6: Log off and Log in again
Step 7: Use Alias (jbt)
Log File Creation
How to create a file containing the output of a command / Shell (Success or Failure).
Add the output of a command to a file
ls -ltr > viveka.temp // Here new file named viveka.tmp will be created in case no file exist with given name and it will have content as the output of given command. If file with given name is there then content of the file will be overridden.
ls -ltr >> viveka.temp // Here new file named viveka.tmp will be created in case no file exist with given name and it will have content as the output of given command. If file with given name is there then content of the file will be appended.
Creating file with error message occurred while executing the command.
find . -name file 2>JBT2 1>JBT2
Here two file will be created JBT1 and JBT2. JBT1 will contain the error message (if any) and JBT2 will contain success message (If any).
How to search for text in executables
nm NCSRGDFS|grep -iw wrt_curr_dt
It will search for something in executable. (GREP will not work in case of executable)
-w it will look for the exact word if you are looking for word @ any position then remove it
find . -name [Aa][Pp][Pp]* -exec grep -ie nextSysDate {} \+
| (Pipe doesn’t work with find so exec needs to be used in case of grep)
