ls Command:
ls command is one of the most frequently used command in Linux.I believe ls command is the first command you may use when you get into the command prompt of Linux Box. We use ls command daily basis and frequently even through we may not aware and never use all the option available.In this article,we'll be discussing basis ls command where we have tried to cover as much parameters as possible
a) List Files using ls with no option
[divakar@divakar BD]# ls
a.txt b.txt
[divakar@divakar BD]#
b) List Files With option –l
[divakar@localhost ~]$ ls -l
-rw-rw-r--. 1 divakar divakar 0 Feb 11 18:51 divakar.txt
-rwxr-xr-x. 1 divakar divakar 0 Feb 12 18:22 diva.txt
c) View Hidden Files
List all files including hidden file starting with ‘.‘.
[divakar@divakar ~]$ ls -al
drwx------. 27 divakar divakar 4096 Feb 21 14:22 .
drwxr-xr-x. 3 root root 4096 Feb 10 13:52 ..
-rw-rw-r--. 1 divakar divakar 0 Feb 11 18:51 divakar.txt
-rwxr-xr-x. 1 divakar divakar 0 Feb 12 18:22 diva.txt
[divakar@localhost ~]$
d) List Files with Human Readable Format with option -lh
With combination of -lh option, shows sizes in human readable format.
[divakar@localhost ~]$ ls -lh
-rw-rw-r--. 1 divakar divakar 0 Feb 12 18:25 d1.txt
-rw-rw-r--. 1 divakar divakar 0 Feb 12 18:25 d2.txt
[divakar@localhost ~]$
e) List Files and Directories with ‘/’ Character at the end
Using -F option with ls command, will add the ‘/’ Character at the end each directory.
[divakar@localhost ~]$ ls -F
d1.txt Desktop/ diva.txt* Downloads/ Pictures/ Templates/ xyz/
d2.txt divakar.txt Documents/ Music/ Public/ Videos/
[divakar@localhost ~]$
f) List Files in Reverse Order
The following command with ls -r option display files and directories in reverse order.
[divakar@localhost ~]$ ls -r
xyz Templates Pictures Downloads diva.txt Desktop d1.txt Videos Public divakar.txt d2.txt
[divakar@localhost ~]$
g) Recursively list Sub-Directories
ls -R option will list very long listing directory trees. See an example of output of the command.
[divakar@localhost ~]$ ls -R
d1.txt Desktop diva.txt Downloads Pictures Templates xyz
h) Reverse Output Order
With combination of -ltr will shows latest modification file or directory date as last.
[divakar@localhost ~]$ ls -ltr
drwxr-xr-x. 2 divakar divakar 4096 Feb 10 18:55 Templates
drwxr-xr-x. 2 divakar divakar 4096 Feb 10 18:55 Downloads
drwxr-xr-x. 2 divakar divakar 4096 Feb 10 18:55 Videos
drwxr-xr-x. 2 divakar divakar 4096 Feb 10 18:55 Public
i) Sort Files by File Size
With combination of -lS displays file size in order, will display big in size first.
[divakar@localhost ~]$ ls -ls
0 -rw-rw-r--. 1 divakar divakar 0 Feb 12 18:25 d1.txt
0 -rw-rw-r--. 1 divakar divakar 0 Feb 12 18:25 d2.txt
4 drwxr-xr-x. 4 divakar divakar 4096 Feb 11 18:03 Desktop
0 -rw-rw-r--. 1 divakar divakar 0 Feb 11 18:51 divakar.
j) Display Inode number of File or Directory
We can see some number printed before file / directory name. With -i options list file /directory with inode number
[divakar@localhost ~]$ ls -i
272870 d1.txt 272869 diva.txt 397175 Pictures 397282 xyz
272871 d2.txt 397173 Documents 397172 Public
k) Shows version of ls command
Check version of ls command.
[divakar@localhost ~]$ ls --version
ls (GNU coreutils) 8.4
Copyright (C) 2010 Free Software Foundation, Inc
l) Show Help Page
List help page of ls command with their option.
[divakar@localhost ~]$ 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.
m) List Directory Information
With ls -l command list files under directory /tmp. Wherein with -ld parameters displays information of /tmp directory.
[divakar@localhost ~]$ ls -l /
dr-xr-xr-x. 2 root root 4096 Feb 10 19:34 bin
dr-xr-xr-x. 5 root root 1024 Feb 10 13:52 boot
n) Display UID and GID of Files
To display UID and GID of files and directories. use option -n with ls command.
[divakar@localhost ~]$ ls -n
-rw-rw-r--. 1 500 500 0 Feb 12 18:25 d1.txt
-rw-rw-r--. 1 500 500 0 Feb 12 18:25 d2.txt
Copying with the cp Command
a) How do I copy files?
cp filename1 filename2 ->
copies a file.
b) How do I copy recursively?
cp –r dir1 dir2
c) To see copy progress pass –v option to cp command.
cp –v –r
dir1 dir2
d) How do I confirm file overwriting?
cp –i dir1 dir2
e) Preserve the file permission and other attributes.
cp –p file1 file2
Deleting Files with the 'rm' Command
The rm command deletes the files.This command has several options,but should be used cautiously.
a) The rm command will delete one or several files from the command line.
rm file1
rm file1 file2 file3
b) One of the safer ways to use rm is through the -i or interactive option, where you'll be asked if you want to delete the file.
rm -i file1
c) you can also force file deletion by using -f option
rm -f file1
d) when we combine -f and -r, the recursive option , you can delete directories and all files or directories found.
rm -rf <directoryname>
Creating Directories with the 'mkdir' Command
The mkdir command can create one or several directories with a single command line.
a) Creating directories
mkdir <directoryName>
b) Creating multiple directories
mkdir <directoryName1> <directoryname2>
c) Creating Child under directories
mkdir temp/child
d) To build a hierarchy of directories with mkdir, you must use the -p,or parent option, for example
mkdir -p temp5/parent/child
Removing Directories with the 'rmdir' Command
a) The rmdir command is used to remove directories. To remove a directory, all you have to do is type
rmdir <DirectoryName>
b) Removing directories and sub directories as well
rm -rf
Renaming Files with the 'mv' command.
The mv command, called a rename command but know to many as a move command
a) Move the data file1 to file2
mv <file1> <file2>
b) The mv command can work silently, or as with rm, you can use the -i (interactive) option
mv -i <file1> <file2>
Creating Hard and Symbolic Links with the 'ln' Command
The ln command creates both types of links.If you use the ln command to create a hard link, you specify a second file on the command line you can use to reference the original file,for Ex
# ln file1 file2
#ln -s file1 file 2
ps command: The ps command will
show information about current system process.
Ps-> The user’s currently running processes.
Ps –f -> Full listing of the user’s currently running process.
ps –ef -> Full listing of all process, except kernel process.
Ps –A -> All process, including kernel process.
Ps auxw -> wide listing sorted by percentage of CPU usage.
Last: The last command shows the
history of who has logged in to the system since the wtmp file was created.
Who: The who command gives this output for each logged-in user:
username,tty .login time and where the user logged in from.
W: The W command is really an extended who
Checking your installation Files
rpm –qa | grep ^x
you should receive the output similar to the following..
xorg-x11-drv-apm-1.2.2-1.1.el6.x86_64
xorg-x11-drv-penmount-1.4.0-5.el6.x86_64
xorg-x11-drv-ast-0.89.9-1.1.el6.x86_64
xorg-x11-drv-aiptek-1.3.0-2.el6.x86_64
Installing the X Files
rpm –ivh <filename>
Moving to different directories
with the cd command.
cd /usr/bin
cd ..
cd ../..
cd or cd –
Knowing where you are with the
pwd command.
pwd
pwd –help
/bin/pwd --help
Searching directories for
matching files with the find command
Syntax: find where-to-look criteria what-to-do
Find /usr –name spell –print
Listing and Combining Files with
the cat Command
The cat (Concatenate file) commands are used to send the contents of
files to your screen.
a) cat a.txt
[abc@master]$ cat a.txt
Hello Hello Hello
Hello hello hello
[abc@master]$
b) The cat command also has a number of options. If you’d like to see your
file with line numbers, you can use the n-option
#cat –n a.txt
1 Hello Hello Hello
2 Hello hello hello
c) You can also use cat to look at several files at once.
# cat –n test*
1 Hello Hello Hello
2 Hello hello hello
[root@localhost ~]# cat a.txt
aksjlkdj
[root@localhost ~]#
[root@localhost ~]# cat b.txt
alksjdjkjaskjkaj
;lajslkdjja
lkashdjfajs
[root@localhost ~]#
d) As you can see, cat has also
include a second file in its output.
[root@localhost ~]# cat a.txt b.txt
aksjlkdj
alksjdjkjaskjkaj
;lajslkdjja
lkashdjfajs
[root@localhost ~]#
cat > c.txt
e) To see the numbers using cat
# cat -n divakar.txt
100 divakar 20000
200 diiia 10000
399 ksjjkj 30999[
Reading the files with the 'more' command
[root@localhost ~]# more c.txt
kajslkj
lkasjdkfjjs
klakjshkdjfhkahs
[root@localhost ~]#
Browsing Files with the 'less' command.
less c.txt
Reading the Beginning or End of
Files with the head and tail Commands.
head -5 /usr/man/man.txt
head -5 –q /usr/man/man.txt
tail -12 /var/log/message/a.txt
The more command is one of a
family of Linux commands called pagers.
Creating Files with the 'touch' Command
The touch command is easy to use, and generally, there are two reasons
to use it .The first reason is to create a file, and the second is to update a
file’s modification date.
a) To create a file with touch,use
# touch newfile
#ls –l newfile
-rw-r--r-- 1 divakar divakar 0 Feb 21 14:12 newfile
b) To Change time stamp
# touch –t 1225110099 newfile2
Trap: when the program is
terminated before it would normal end, we can catch an exit signal.
0-
Normal termination, end of script.
1-SIGHUP -> hang up, line
disconnected
2-singint-> terminal interrupts,
usually ctrl+c
3- SIGQUIT -> Quit Key, Child process
to die before terminating.
9-SIGKILL->kill -9 commands can’t
trap this type of exit status.
15-SIGTERM Ã kill
command’s default action.
19-SIGSTOP->stop, usually ctrl+z
17 -> dintfunc
Ex: Kill
–9 <ps Id>
df -> Report how much free
disk space is available for each mount you have.
df –a
--all -> include dummy file system.
df –B
100, --block-size=SIZE -> use SIZE –byte blocks
df –h ->human readable à print sizes in human
readable format.
df –I -> list inode information
instead of block usage.
Df –k -> like --block –Size =1 k.
df –T ->Print file System Type.
du -> disk usage
du ->tells you how much disk space a
file occupies.
du –a ->display the space that each file is taking up.
Du –h -> which can make the output
easier to read by displaying it in KB /M/G.
Du –sh -> The -s (for suppress or summarize)
option tells du to report only the total disk space occupied by a directory
tree and to suppress individual reports for its subdirectories
top à displays
top CPU process.
The top program provides a dynamic real-time
view of a running system.
Uname
Free -> displays information
about free and used memory on the system.
-b,-k,-m,-g show output in bytes, KB,
MB, or GB
-l show detailed low and high memory
statistics
-o use old format (no -/+buffers/cache
line)
-t display total for RAM + swap
-s update every [delay] seconds
-c update [count] times
-V display version information and exit
awk-> The awk command is
powerful method for processing or analyzing text files,in particulat data files
that are organized by lines (rows) and cloumns.
How to add user:
Useradd div --to add user Id
Passwd div –to set password
Set Account disable date:
useradd
-e {yyyy-mm-dd} {username}
useradd -e 2008-12-31 jerry
Set default password expiry:
useradd -f {days} {username}
useradd -e 2009-12-31 -f 30 jerry
How Can I see the entire users list on Linux Server?
cat /etc/passwd
Vim /etc/passwd
cat /etc/passwd | grep
home | cut -d':' -f1
How to convert you as root, create new user and setting
password.
[divakar@localhost
Desktop]$ su root
Password: <give your
user passwd>
[root@localhost
Desktop]# useradd diva1
[root@localhost Desktop]#
passwd diva1
Changing password for
user diva1.
New password:
BAD PASSWORD: it is too
short
BAD PASSWORD: is too
simple
Retype new password:
passwd: all
authentication tokens updated successfully.
[root@localhost
Desktop]#
How to add user in sudo list.
Go to vi /etc/sudoers
## Allow root to run any
commands anywhere
root ALL=(ALL) ALL
divakar ALL=(ALL)
ALL
Man ->
Find files with the whereis
command.
Whereis find
You can also use whereis to find only the binary version of the program
with
Whereis –b find
If whereis cann’t find your request , you’ll get an empty return
string, for example
Whreis foo
It will search in entire system.
Not limiting searches to known directories such as /usr/man, /usr/bin,
or /usr/sbin can speed up the task of finding files.
Although whereis is faster than using find to locate programs or manual
pages.
Locate is faster than whereis
Locating files with locate
command.
Finding a file using locate is much faster than the find command
because locate will go directly to the database file,find any matching
filenames, and print its results.
Locate *.ps
Locate resides in /var/lib
Moving different directories
with cd command.
cd or
cd ../.. or
cd or cd –
Knowing where you are wit pwd
command.
Go to /user/local and type pwd to know your directory.
ps -ef | grep aneel
pkill -f
Link while copying the data?
cp –i test 1 test2
Getting command Summaries with
whatis and apropos
Specifying other directories
with ls
# ls /usr/bin
Listing Directories with the dir
and vdir commands
#dir :-> this command works like the default ls command,listing the
files in sorted columns
Vdir -> The vdir command works like the ls –l option, and presents a
long format listing by default,
Graphic Directory listings with the tree command
# tree /var/lib
# tree –d /usr/local/netscape/
Search Inside Files with the 'grep' Command
grep command will help to search any words in file
Ex: cat hive.log | grep loaded [Here we are searching loaded files in log]
Compressing files with the 'gzip' command
# gzip file.tar
Compressing Files with the 'compress' Command
#compress file
To uncompress a file,use
# uncompress file.Z
Running Programs in the Background
# nohup ./divakar.sh &
Checking the Connection
Using the 'ipconfig' Command, This Command will help to identify the IP address of your system
# ifconfig
[divakar@localhost ~]$ ifconfig
eth0 Link encap:Ethernet HWaddr 00:0C:29:7F:24:89
inet addr:192.168.64.130 Bcast:192.168.64.255 Mask:255.255.255.0
inet6 addr: fe80::20c:29ff:fe7f:2489/64 Scope:Link
Using the 'netstat' Command
The netstat command is the definitive command for checking your network activity,connections,routing tables,and other network messages and statistics.
# netstat
Using the ping Command
# ping <hostname>.com
Find Hostname of the System
#hostname
How to replace One word with another word in vi:
:%s/old-text/new-text/g
Hadoop File system Commands
The FileSystem (FS) shell is invoked by bin/hadoop fs <args>. All the FS shell commands take path URIs as arguments. The URI format is scheme://autority/path. For HDFS the scheme is hdfs, and for the local filesystem the scheme is file. The scheme and authority are optional. If not specified, the default scheme specified in the configuration is used. An HDFS file or directory such as /parent/child can be specified as hdfs://namenodehost/parent/child or simply as /parent/child (given that your configuration is set to point to hdfs://namenodehost). Most of the commands in FS shell behave like corresponding Unix commands. Differences are described with each of the commands. Error information is sent to stderr and the output is sent to stdout.
Ex : hadoop fs -ls /R
[-ls <path>]
[-lsr <path>]
[-df [<path>]]
[-du <path>]
[-dus <path>]
[-count[-q] <path>]
[-mv <src> <dst>]
[-cp <src> <dst>]
[-rm [-skipTrash] <path>]
[-rmr [-skipTrash] <path>]
[-expunge]
[-put <localsrc> ... <dst>]
[-copyFromLocal <localsrc> ... <dst>]
[-moveFromLocal <localsrc> ... <dst>]
[-get [-ignoreCrc] [-crc] <src> <localdst>]
[-getmerge <src> <localdst> [addnl]]
[-cat <src>]
[-text <src>]
[-copyToLocal [-ignoreCrc] [-crc] <src> <localdst>]
[-moveToLocal [-crc] <src> <localdst>]
[-mkdir <path>]
[-touchz <path>]
[-test -[ezd] <path>]
[-stat [format] <path>]
[-tail [-f] <file>]
[-chmod [-R] <MODE[,MODE]... | OCTALMODE> PATH...]
[-chown [-R] [OWNER][:[GROUP]] PATH...]
[-chgrp [-R] GROUP PATH...]
[-help [cmd]]
distcp:
hadoop distcp <Source Directory> <Destination Directory>
lsblk :To display block device information
[root@uuuuuuu]# lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 2.7T 0 disk
├─sda1 8:1 0 200M 0 part /boot/efi
├─sda2 8:2 0 512M 0 part /boot
├─sda3 8:3 0 500G 0 part
│ ├─RootVolGroup00-lv_root (dm-0) 253:0 0 16G 0 lvm /
│ ├─RootVolGroup00-lv_swap (dm-1) 253:1 0 32G 0 lvm [SWAP]
│ ├─RootVolGroup00-lv_var (dm-2) 253:2 0 16G 0 lvm /var
│ ├─RootVolGroup00-lv_opt (dm-3) 253:3 0 15G 0 lvm /opt
│ ├─RootVolGroup00-lv_home (dm-4) 253:4 0 15G 0 lvm /home
│ ├─RootVolGroup00-lv_optmapr (dm-5) 253:5 0 200G 0 lvm /opt/mapr
│ └─RootVolGroup00-lv_optcores (dm-6) 253:6 0 100G 0 lvm /opt/cores
└─sda4 8:4 0 2.2T 0 part
How to Check installed packages:
# rpm -qa | grep hive
To Locate Java:
# locate java | grep bin |less
General Startup on VI
To use vi: vi filename
To exit vi and save changes:
ZZ or
:wq
To exit vi without saving
changes: :q!
To enter vi command mode:
[esc]
Counts
A number preceding any vi
command tells vi to repeat that command
that many times.
Cursor Movement
h move left (backspace)
j move down
k move up
l move right (spacebar)
[return] move to the beginning of the
next line
$ last column on the
current line
0 move cursor to the first
column on the current line
^ move cursor to first
nonblank column on the current line
w move to the beginning of
the next word or punctuation mark
W move past the next space
b move to the beginning of
the previous word or punctuation mark
B move to the beginning of
the previous word,ignores punctuation
e end of next word or
punctuation mark
E end of next word,
ignoring punctuation
H move cursor to the top of
the screen
M move cursor to the middle
of the screen
L move cursor to the bottom
of the screen Screen Movement
G move to the last line in
the file
xG move to line x
z+ move current line to top
of screen
z move current line to the
middle of screen
z- move current line to the
bottom of screen
^F move forward one screen
^B move backward one line
^D move forward one half
screen
^U move backward one half
screen
^R redraw screen ( does not
work with VT100 type terminals )
^L redraw screen ( does not
work with Televideo terminals ) Inserting
r replace character under cursor with
next character typed
R keep replacing character
until [esc] is hit
i insert before cursor
a append after cursor
A append at end of line
O open line above cursor
and enter append mode
Deleting
x delete character under
cursor
dd delete line under cursor
dw delete word under cursor
db delete word before cursor
Copying Code
yy (yank)'copies' line which
may then be put by the p(put) command.
Precede with a count for
multiple lines.
Put Command brings back previous deletion or yank of lines,words, or
characters
P bring back before cursor
p bring back after cursor
Find Commands
? finds a word going
backwards
/ finds a word going
forwards
f finds a character on the
line under the cursor going forward
F finds a character on the
line under the cursor going backwards
t find a character on the
current line going forward and stop one character before it
T find a character on the
current line going backward and stop one character before it;
repeat last f, F, t, T
Miscellaneous Commands
. repeat last
command
u undoes last command
issued
U undoes all commands
on one line
xp deletes first
character and inserts after second (swap)
J join current line
with the next line
^G display current line
number
% if at one
parenthesis, will jump to its mate
mx mark current line with
character x
'x find line marked
with character x
NOTE: Marks are
internal and not written to the file.
Line Editor Mode
Any commands form the line editor ex can be issued upon entering line mode.
To enter: type ':
To exit: press[return] or [esc]
ex Commands
For a complete list consult the
UNIX Programmer's Manual
READING FILES
copies (reads) filename after cursor in file currently editing
:r filename
WRITE FILE
:w saves the current
file without quitting
MOVING
:# move to line #
:$ move to last line of
file
SHELL ESCAPE
executes 'cmd' as a shell command.
:!'cmd'
$ scp foobar.txt your_username@remotehost.edu:/some/remote/directory
MapR Regular Commands
Use the following commands to list MapR services
maprcli service list
