Know the UNIX Commands

U N I X
made by B Chari K working in semiconductors domain

UNIX OS
 Unix is a multi-user, multi-tasking, multi-
processing, efficient, fast and very powerful
operating system.
 The OS is build on top of the kernel, and
consists of
additional commands,
utilities,
command interpreters or shells,
language compilers and debuggers,
text processors etc.
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Kernel
 The kernel is the heart of the any operating
system.
 This is relatively small piece of code that
directly sits on the hardware.
 It is a collection of programs that are mostly
written in C
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Shell Prompt
 Shell provides an interface to the user and UNIX
OS.
 A shell is an environment in which we can run our
commands, programs, and shell scripts.
 It gathers input from user and executes programs
based on that input.
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Different shells
 Different flavor of
shells, each has own
set of recognized
commands and
functions
 Borne shell(sh)
 Korn shell(sh)
 C shell
 TENEX C
shell(tcsh)
 Shells are usually
installed in /bin/B Chari K

Super User
 Unix is a case-sensitive operating system.
 A special account root that is reserved for the
system administrator or super user.
 It has all system resources, including all files,
directories, and data.
 The super user has full access and control
over every thing and a slight mistake can cause
irreparable damage to the system.
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Absolute path & Relative path
 Absolute path : starts from root(/) and follow the
tree
 Relative path : starts from current directory
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Changing directory
 cd is used to change from
one directory to another
directory
cd ~  to home directory
cd /  to root directory
cd -  to last directory
cd ..  to immediate parent
directory
cd <dir_name> or cd <path>
pwd  know the path for
current directory
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Creating and Removing Directories
 mkdir creates a
directory
mkdir <dir_name>
mkdir path>/<dir_name>
 rmdir removes a
directory
rmdir <dir_name>
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Listing Files
 ls list the files and
directories in current
directory
 ls –l  long listing the all
details of files
 ls –a  hidden files
 ls –t  sort the files
 Ls -R recursively
displays all files in
subdirectories
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Creating Files
touch is used to create
new, empty files
touch <file_name>
The argument to the
command taken as new
file name
Touch
<fie1><file2><file3>
Can create any no.of files
simultaneously
This command can
change timestamps for
existing files
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Creating and Editing files
vi editor to create an
ordinary files
vi <file_name>
Press i - come into insert
mode
esc - come to command
mode
:wq to save and come out
of file completely.
vim, gvim, gedit, nedit,
emacs are some of editors
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Display or concatenate files
cat displays the file
content on terminal.
Or display two files’
contents together
cat file1 file2
Combines and displays
file1 and file2
cat file1 file2 > filex
Moves file1 and file2
to filex
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Chmod 755 <file1>
Change permissions
chmod alters the
permissions on files and
directories using either
symbolic or octal numeric
codes.
+ to add a permission
- to add a permission
= to assign a permission
chmod u=rw <file1>
chmod u+x, g+w, o-w
<file1>
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Copying and Moving files
cp used to make
copies of files and
directories
Cp <source_file>
<destination_file>
Cp file1 file2 dir1
Copies file1 and file2
into dir1 directory
Cp –r dir1 dir2
Copies directories
using -r
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Moving and Renaming files
mv used to change the
name of the files or move
the files into other
directories
mv file1 file2
Renames the file1 to
file2
mv file1 file2 dir1
Moves file1 and file2
to dir1 directory
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Getting help
man used to get the
manuals pages about the
command
man <command>
(or)
<command> --help
Info used to get the
description of all available
commands.
info
Info <command>
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Removing files
rm is used to remove
files
rm <file1>
Deletes the existing file
rm -i <file1>
You will be asked that
you wish to be delete or
not
rm -r <directory>
Recursively deletes the
contents of directory,
its subdirectories and
deletes directory itself
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Commands on files
Sort this command sort
and combines all the lines in
file
Sort -d <file1>
Sorts based on
dictionary order in which
letters, digits,
whitespaces considered
Sort -r <file1>
Reverse the order of
the combining sequence
diff display difference
between two files
Diff <file1> <file2>
Reports line by line
difference between the text
files
file tests named files to
determine the categories their
contents belongs to.
File <file1>
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Display commands
echo prints the given
argument in standard output
device
echo “type a string”
head displays the head
or start of the file
head -number <file1>
Head -10 file1
taildisplays the tail or end of
the file
tail -number <file1>
Tail -20 <file1>
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Display commands(more, less)
more display the large
file in one screenful at a time
more <file1>
Allows only forward
control
less similar to more
Less <file1>
Allows forward and
backward movement
more, less can also be
used for pattern searching
 more +/pattern <file1>
Less +/pattern <file1>
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System resource commands
date report current
date and time
which reports path for
the specified command
which <command>
du report the disk
usage of specified file or
directory
du <dirname>
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System resource commands
uname display or set the
name of the current machine
passwd change or set
the password
who report who is logged
in and what processes are
running
script saves everything that
appears on the screen to a file
until exit is executed.
script <file>
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Find files of a specified name or
type
find searches for files in
a named directory and all its
subdirectories.
find . -type f -name “*.txt”
Searches current directory
for the files end with .txt
extension
find < > -type < > -name “pattern”
Path from where
You want to search
d – directory
f – files
l - link
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Pattern Matching
grep searches for lines
containing specified pattern
grep <pattern>
<file_name>
grep -i <pattern>
<file_name>
For insensitive
search
grep -wocv <pattern>
<file>
-w Prints line which
have individual word
-o it prints only the
word
-c it gives the count
-v prints lines which
didn't match
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Piping
 Connect two commands together so that the
output from one program becomes the input of
the next program.
 ls –l | grep “Aug”
 This would extract all the files created in August
month
B Chari K

T h a n k Y o u
made by B Chari K working in semiconductors domain

Know the UNIX Commands

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