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Linux Commands – Basic commands

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Linux is a intensely fix and secured reply source nimble system. I will attempt to explain some totally basic level of commands which are commonly used:

There are two types of commands, shell commands and linux commands.

Shell Commands

Shell commands are share of the shell program. There are several oscillate shells (C shell, bash shell, bourne shell etc) to pick from, and each will have a variation of the shell commands built in. The commands adjust between shells, but each shell is the connected across every second linux distros.

Linux Commands

Linux commands are not part of the shell. Each one is a separate executable program, probably written in the C programming language.
These executable s are stored in various directories set up for binary files, such as /bin and /usr/bin. The location of these directories can be defined with the $PATH variable so the shells know where to find them. These commands vary between different linux distributions, and remain the same whichever shell you are using.

The Command Prompt

What your prompt looks like will depend on the shell you use (bash, borne, csh etc), and the settings you have for that shell.
I use a bash shell, and have the prompt set up to look like this……

[root@cirrus home]#

This shows me I am logged in as root, to the computer called cirrus, and I am in a folder called home.
TIP: To see the full path of the folder ‘home’, use the pwd command.

Your prompt is bound to look different, so for the purpose of this section I will just use the > to represent the prompt.

Show is a list of commonly used commands with explanations aimed at Linux command prompt beginners.
Command Example Description
cat Sends file contents to standard output. This is a way to list the contents of short files to the screen. It works well with piping.
cat .bashrc Sends the contents of the “.bashrc” file to the screen.
cd Change directory
cd /home Change the current working directory to /home. The ‘/’ indicates relative to root, and no matter what directory you are in when you execute this command, the directory will be changed to “/home”.
cd httpd Change the current working directory to httpd, relative to the current location which is “/home”. The full path of the new working directory is “/home/httpd”.
cd .. Move to the parent directory of the current directory. This command will make the current working directory “/home.
cd ~ Move to the user’s home directory which is “/home/username”. The ‘~’ indicates the users home directory.
cp Copy files
cp myfile yourfile Copy the files “myfile” to the file “yourfile” in the current working directory. This command will create the file “yourfile” if it doesn’t exist. It will normally overwrite it without warning if it exists.
cp -i myfile yourfile With the “-i” option, if the file “yourfile” exists, you will be prompted before it is overwritten.
cp -i /data/myfile . Copy the file “/data/myfile” to the current working directory and name it “myfile”. Prompt before overwriting the file.
cp -dpr srcdir destdir Copy all files from the directory “srcdir” to the directory “destdir” preserving links (-p option), file attributes (-p option), and copy recursively (-r option). With these options, a directory and all it contents can be copied to another directory.
dd dd if=/dev/hdb1 of=/backup/ Disk duplicate. The man page says this command is to “Convert and copy a file”, but although used by more advanced users, it can be a very handy command. The “if” means input file, “of” means output file.
df Show the amount of disk space used on each mounted filesystem.
less less textfile Similar to the more command, but the user can page up and down through the file. The example displays the contents of textfile.
ln Creates a symbolic link to a file.
ln -s test symlink Creates a symbolic link named symlink that points to the file test Typing “ls -i test symlink” will show the two files are different with different inodes. Typing “ls -l test symlink” will show that symlink points to the file test.
locate A fast database driven file locator.
slocate -u This command builds the slocate database. It will take several minutes to complete this command. This command must be used before searching for files, however cron runs this command periodically on most systems.
locate whereis Lists all files whose names contain the string “whereis”.
logout Logs the current user off the system.
ls List files
ls List files in the current working directory except those starting with . and only show the file name.
ls -al List all files in the current working directory in long listing format showing permissions, ownership, size, and time and date stamp
more Allows file contents or piped output to be sent to the screen one page at a time.
more /etc/profile Lists the contents of the “/etc/profile” file to the screen one page at a time.
ls -al |more Performs a directory listing of all files and pipes the output of the listing through more. If the directory listing is longer than a page, it will be listed one page at a time.
mv Move or rename files
mv -i myfile yourfile Move the file from “myfile” to “yourfile”. This effectively changes the name of “myfile” to “yourfile”.
mv -i /data/myfile . Move the file from “myfile” from the directory “/data” to the current working directory.
pwd Show the name of the current working directory
more /etc/profile Lists the contents of the “/etc/profile” file to the screen one page at a time.
shutdown Shuts the system down.
shutdown -h now Shuts the system down to halt immediately.
shutdown -r now Shuts the system down immediately and the system reboots.
whereis Show where the binary, source and manual page files are for a command
whereis ls Locates binaries and manual pages for the ls command.

 

For easy and better understanding of Linux – Shell refer Here

For a complete bash commands click here

 

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