Basic unix commands

Linju C John
Jerin Mathew George
S5 MCA

 date: Used to display the current system date and
time.
Eg:
[vijai@localhost vijai]$ date
Sat Apr 9 13:03:47 IST 2011
 date +%D: Displays date only.
Eg:
[vijai@localhost vijai]$ date +%D
04/09/11
General Commands

 date +%T: Displays time only
[vijai@localhost vijai]$ date +%T
13:05:33
 date +% Y: Displays the year part of date
[vijai@localhost vijai]$ date +%Y
2011
 date +% H: Displays the hour part of time
[vijai@localhost vijai]$ date +%H
13

 cal: Calendar of the current month
[vijai@localhost vijai]$ cal
April 2011
Su Mo Tu We Th Fr Sa
1 2
3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30

 cal year: Displays calendar for all months of the
specified year
[vijai@localhost vijai]$ cal 1800
1800
#shows full calender of 1800

 cal month year: Displays calendar for the specified
month of the year
[vijai@localhost vijai]$ cal 08 1998
August 1998
Su Mo Tu We Th Fr Sa
1
2 3 4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31

 who: Login details of all users such as their IP,
Terminal No, User name
[vijai@localhost vijai]$ who
root :0 Apr 9 08:41
vijai pts/0 Apr 9 13:00 (scl-64)
cse1 pts/3 Apr 9 13:18 (scl-41.smkfomra.com)
ecea pts/4 Apr 9 13:18 (scl-29.smkfomra.com)
 who am i: Used to display the login details of the user
[vijai@localhost vijai]$ who am i
vijai pts/0 Apr 9 13:00 (scl-64)

 tty: Used to display the terminal name
[vijai@localhost vijai]$ tty
/dev/pts/0
 uname: Displays the Operating System
[vijai@localhost vijai]$ uname
Linux
 uname –r: Shows version number of the OS (kernel).
[vijai@localhost vijai]$ uname -r
2.4.20-8smp

 uname –n: Displays domain name of the server
[vijai@localhost vijai]$ uname -n
localhost.localdomain
 echo "txt“: Displays the given text on the screen
[vijai@localhost vijai]$ echo "How are you"
How are you

 echo $HOME: Displays the user's home directory
[vijai@localhost vijai]$ echo $HOME
/home/vijai
[vijai@localhost vijai]$ echo $USER
vijai

 bc: Basic calculator. Press Ctrl+d to quit
[vijai@localhost vijai]$ bc
bc 1.06
Copyright 1991-1994, 1997, 1998, 2000 Free
Software Foundation, Inc.
3+5
8 2%3
2

 man cmdname: Manual for the given command.
Press q to exit
 history: To display the commands used by the user
since log on.
 exit: Exit from a process. If shell is the only process
then logs out

 pwd: Path of the present working directory
[vijai@localhost loops]$ pwd
/home/vijai/shellscripts/loops
 mkdir dir: A directory is created in the given name
under the current directory
 mkdir dir1 dir2: A number of sub-directories can be
created under one stroke
[vijai@localhost vijai]$ mkdir filter
[vijai@localhost vijai]$ ls
filter list.sh regexpr shellscripts
Directory Commands

 cd subdir: Change Directory. If the subdir starts with /
then path starts from root (absolute) otherwise from
current working directory.
[vijai@localhost vijai]$ cd shellscripts/loops/
[vijai@localhost loops]$
[vijai@localhost loops]$ cd
[vijai@localhost vijai]$

 cd: To switch to the home directory.
[vijai@localhost loops]$ cd /
[vijai@localhost /]$
 cd /: To switch to the root directory.
[vijai@localhost /]$cd/home/vijai/shellscripts/loops/

 cd ..: To move back to the parent directory
[vijai@localhost loops]$ cd ..
[vijai@localhost shellscripts]$
 rmdir subdir: Removes an empty sub-directory.
[vijai@localhost vijai]$ rmdir filter
list.sh regexpr shellscripts

 cat > filename: To create a file with some contents. To
end typing press Ctrl+d. The > symbol means
redirecting output to a file. (< for input)
[vijai@localhost vijai]$ cat > greet
hi s5mca
wishing u the best
 cat filename: Displays the file contents.
[vijai@localhost vijai]$ cat greet
hi s5mca
wishing u the best
File Commands

 cat >> filename: Used to append contents to a file
[vijai@localhost vijai]$ cat >> greet
bye
[vijai@localhost vijai]$ cat greet
hi s5mca
wishing u the best
bye

 cp src des: Copy files to given location. If already exists, it
will be overwritten
[vijai@localhost vijai]$ cp greet ./regexpr/
greet list.sh regexpr shellscripts
[vijai@localhost vijai]$ ls ./regexpr
demo greet
 cp –r src des: Copies the entire directory, all its sub-
directories and files.
 cp –i src des: Warns the user prior to overwriting the
destination file
[vijai@localhost vijai]$ cp -i greet ./regexpr/
cp: overwrite 'greet'? n

 mv old new: To rename an existing file or directory. –i
option can also be used
 mv f1 f2 f3 dir: To move a group of files to a directory.
 mv –v old new: Display name of each file as it is
moved.
[vijai@localhost vijai]$ mv greet greet.txt
greet.txt list.sh regexpr shellscripts
[vijai@localhost vijai]$ mv greet.txt ./regexpr/
[vijai@localhost vijai]$ ls ./regexpr/
demo greet.txt

 rm file: Used to delete a file or group of files. –i option
can also be used
 rm *: To delete all the files in the directory.
 rm –r *: Deletes all files and sub-directories
 rm –f *: To forcibly remove even write-protected files
[vijai@localhost vijai]$ rm -i *.sh
rm: remove regular file `fact.sh'? y
rm: remove regular file `list.sh'? n
rm: remove regular file `prime.sh'? y

 ls: Lists all files and subdirectories (blue colored) in
sorted manner.
greet list.sh regexpr shellscripts
 ls name: To check whether a file or directory exists.
 ls name*: Short-hand notation to list out filenames of
a specific pattern.
 ls –a: Lists all files including hidden files (files
beginning with .)
[vijai@localhost vijai]$ ls -a
. .bash_logout .canna .gtkrc regexpr .viminfo.tmp
.. .bash_profile .emacs .kde shellscripts .xemacs
.bash_history .bashrc greet list.sh .viminfo

 ls –x dirname: To have specific listing of a directory.
 ls –R: Recursive listing of all files in the subdirectories
 ls –l: Long listing showing file access rights
(read/write/execute-rwx for user/group/others-ugo).
[vijai@localhost vijai]$ ls -l
total 16
-rw-rw-r-- 1 vijai vijai 32 Apr 11 14:52 greet
-rw-rw-r-- 1 vijai vijai 30 Apr 4 13:58 list.sh
drwxrwxr-x 2 vijai vijai 4096 Apr 9 14:30 regexpr
drwxrwxr-x 7 vijai vijai 4096 Apr 4 14:57
shellscripts

 cmp file1 file2: Used to compare two files. Displays
nothing if files are identical.
[vijai@localhost vijai]$ cmp list.sh fact.sh
list.sh fact.sh differ: byte 1, line 1
 wc file: It produces a statistics of lines (l), words(w),
and characters(c).
[vijai@localhost vijai]$ wc list.sh
4 9 30 list.sh
[vijai@localhost vijai]$ wc -l list.sh
4 list.sh

 chmod perm file: Changes permission for the
specified file. (r=4, w=2, x=1, Owner=u, Group=g,
Others=o)
[vijai@localhost vijai]$ ls -l list.sh
-rw-rw-r-- 1 vijai vijai 30 Apr 4 13:58 list.sh
[vijai@localhost vijai]$ chmod ug+x list.sh
-rwxrwxr-- 1 vijai vijai 30 Apr 4 13:58 list.sh
[vijai@localhost vijai]$ chmod 740 list.sh
-rwxr----- 1 vijai vijai 30 Apr 4 13:58 list.sh

 head: Used to display the first few records (10 records by
default)
[vijai@localhost filters]$ head stud
20057801|Aarthi |ECE |CTS |36000
20057702|Albert Jerry |CSE |Wipro |25000
20057903|Arun |IT |Ramco |12000
20057904|Diwakar |IT |TCS |10500
20057705|Geetha |CSE |Infosys |23000
20057806|Irudayaraj |ECE |Polaris |30000
20057707|Jaya Prakash |CSE |Ramco |28000
20058008|Mahesh |EEE |Microsoft |5000
20057909|Manimaran |IT |Microsoft |9000
20058010|Mohammed Mukthar |EEE |Oracle |6000

 head -5: stud Displays first 5 records
[vijai@localhost filters]$ head -4 stud
20057801|Aarthi |ECE |CTS |36000
20057903|Arun |IT |Ramco |12000
20057904|Diwakar |IT |TCS |10500
 head -1 stud | wc –c: length of first record
[vijai@localhost filters]$ head -1 stud | wc -c
49

 Tail: Used to display the last few records (10 records by
default)
[vijai@localhost filters]$ tail stud
20057711|Prithivi Rajan |CSE |Ramco |25000
20057712|Pushpak Chander |CSE |CTS |27500
20057713|Ramesh |CSE |Wipro |24000
20057817|Smitha |ECE |Ramco |30000
20057718|Sri Gurumoorthy |IT |Microsoft |11000
20057719|Tamil Selvi |EEE |CTS |3500
20057720|Thamotharan |IT |CTS |9000

 tail -5 stud | tee last5: Last 5 records listed & stored
in file last5 using tee
[vijai@localhost filters]$ tail -2 stud | tee last2
[vijai@localhost filters]$ cat last2

 cut: Used to extract specific fields. The d option
specifies the delimiter and f for specifying the field
list. The c option may be used if extraction is done
character wise
cut –d | -f 1,3,4 stud Fields 1,3,4 listed
cut –d | -f 2-4 stud Fields 2,3,4 listed
paste –d | list1 list2 merges two cut files list1
and list2

[vijai@localhost filters]$ cut -d | -f 1-3 stud
20057801|Aarthi |ECE
20057702|Albert Jerry |CSE
20057903|Arun |IT
20057904|Diwakar |IT
20057705|Geetha |CSE
20057806|Irudayaraj |ECE
20057707|Jaya Prakash |CSE
20058008|Mahesh |EEE
20057909|Manimaran |IT
20058010|Mohammed Mukthar |EEE
20057711|Prithivi Rajan |CSE
20057712|Pushpak Chander |CSE
20057713|Ramesh |CSE
20057817|Smitha |ECE
20057718|Sri Gurumoorthy |IT
20057719|Tamil Selvi |EEE
20057720|Thamotharan |IT

 sort: reorders the file as per ASCII sequence. The t option is used to
specify delimiter sort stud Sorted on 1st column by default
[vijai@localhost filters]$ sort stud
20057801|Aarthi |ECE |CTS |36000
20057903|Arun |IT |Ramco |12000
20057904|Diwakar |IT |TCS |10500

 sort –t | +2 stud: Sort as per 3rd column
[vijai@localhost filters]$ sort -t | +1 stud
20057801|Aarthi |ECE |CTS |36000
20057903|Arun |IT |Ramco |12000
20057904|Diwakar |IT |TCS |10500

 nl:display file content with lines numbered. The s option is used to
specify separator
 nl –s "|" stud Displays entries numbered with separator |
[vijai@localhost filters]$ nl -s "|" stud
1|20057801|Aarthi |ECE |CTS |36000
2|20057702|Albert Jerry |CSE |Wipro |25000
3|20057903|Arun |IT |Ramco |12000
4|20057904|Diwakar |IT |TCS |10500
5|20057705|Geetha |CSE |Infosys |23000
6|20057806|Irudayaraj |ECE |Polaris |30000
7|20057707|Jaya Prakash |CSE |Ramco |28000
8|20058008|Mahesh |EEE |Microsoft |5000
9|20057909|Manimaran |IT |Microsoft |9000
10|20058010|Mohammed Mukthar |EEE |Oracle |6000
11|20057711|Prithivi Rajan |CSE |Ramco |25000
12|20057712|Pushpak Chander |CSE |CTS |27500
13|20057713|Ramesh |CSE |Wipro |24000
14|20057817|Smitha |ECE |Ramco |30000
15|20057718|Sri Gurumoorthy |IT |Microsoft |11000
16|20057719|Tamil Selvi |EEE |CTS |3500
17|20057720|Thamotharan |IT |CTS |9000

 tr: Translates characters. Can be used to change text case. It works
with standard input <
 tr '[a-z]' '[A-Z]' < stud: Changes text to upper case
[vijai@localhost filters]$ tr '[a-z]' '[A-Z]' < stud
20057801|AARTHI |ECE |CTS |36000
20057702|ALBERT JERRY |CSE |WIPRO |25000
20057903|ARUN |IT |RAMCO |12000
20057904|DIWAKAR |IT |TCS |10500
20057705|GEETHA |CSE |INFOSYS |23000
20057806|IRUDAYARAJ |ECE |POLARIS |30000
20057707|JAYA PRAKASH |CSE |RAMCO |28000
20058008|MAHESH |EEE |MICROSOFT |5000
20057909|MANIMARAN |IT |MICROSOFT |9000
20058010|MOHAMMED MUKTHAR |EEE |ORACLE |6000
20057711|PRITHIVI RAJAN |CSE |RAMCO |25000
20057712|PUSHPAK CHANDER |CSE |CTS |27500
20057713|RAMESH |CSE |WIPRO |24000
20057817|SMITHA |ECE |RAMCO |30000
20057718|SRI GURUMOORTHY |IT |MICROSOFT |11000
20057719|TAMIL SELVI |EEE |CTS |3500
20057720|THAMOTHARAN |IT |CTS |9000

 grep this demo: Lists the lines that contains the string
this
[vijai@localhost regexpr]$ grep this demo
this line is the 1st lower case line in this file.
Two lines above this line is empty.
 grep 'end of' demo: Quotes mandatory for text containing
space
[vijai@localhost regexpr]$ grep 'end of' demo
1. e - go to the end of the current word.
2. E - go to the end of the current WORD.
 grep this demo* Search this in multiple files

 grep –c to demo: Number of occurrence of the word
to in the file
[vijai@localhost regexpr]$ grep -c to demo
5
 grep –n sequence demo: Display line numbers along
with matching lines
[vijai@localhost regexpr]$ grep -n sequence
demo
15:WORD - WORD consists of a sequence of non-
blank characters
16:Word - word consists of a sequence of letters,
digits and underscores.

 grep –v word demo: Displays lines that does not contain
the text word
[vijai@localhost regexpr]$ grep -v word demo
THIS LINE IS THE 1ST UPPER CASE LINE IN THIS
FILE.
This Line Has All Its First Character Of The Word
With Upper Case.
Two lines above this line is empty.
vim Word Navigation
4. B - go to the previous WORD.
WORD - WORD consists of a sequence of non-blank
characters
telnet 172.16.4.256

 grep –i WORD demo: Search for text ignoring case
differences
[vijai@localhost regexpr]$ grep -i WORD demo
This Line Has All Its First Character Of The Word
With Upper Case.
vim Word Navigation
You may want to do several navigation in relation to
words, such as:
3. b - go to the previous word.
WORD - WORD consists of a sequence of non-blank
characters
Word - word consists of a sequence of letters, digits
and underscores.

 grep '^[0-9]' demo: Lines that start with a number
[vijai@localhost regexpr]$ grep '^[0-9]' demo
 grep '[0-9]$' demo: Lines that end with a number
[vijai@localhost regexpr]$ grep '[0-9]$' demo
telnet 172.16.4.256

 grep "2....$" stud: Display lines that ends in the range
20000–29999
 egrep "lower|UPPER" demo: Display lines that
match either lower or upper
[vijai@localhost regexpr]$ egrep "lower|UPPER"
demo
THIS LINE IS THE 1ST UPPER CASE LINE IN
THIS FILE.

 egrep "(previous|current)word" demo: Display
lines that match either previous word or current word
[vijai@localhost regexpr]$ egrep
"(previous|current) word" demo
 touch: Create a new file.
[vijai@localhost regexpr]$ touch jmg
[vijai@localhost regexpr]$ ls
jmg demo

 kill: Terminates a process.
kill [options] <process-number>
$kill -9 absolute kill.

Basic unix commands

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Basic unix commands