Various flavors of UNIX

Various flavors of UNIX
  • AIX--major--IBM's version that runs on the RS/6000 series of RISC systems and mainframes. Over 500,000 RS/6000 systems have been sold!
  • BSD--minor--This version has a lesser presence in the marketplace. Although many variants can trace their heritage to BSD, it is not that popular as a product.
  • HP-UX--major--Hewlett Packard's (HP) version with a strong hardware presence in the marketplace and a strong future growth path.
  • IRIX--minor--While the Silicon Graphics (SGI) machines are wonderful for graphics, they have not found wide acceptance in business environments.
  • Linux--minor--Although this is a very nice and free variant, it has little commercial presence in the marketplace (probably because corporations do not want to run their mission-critical applications without a vendor they can sue when there is a problem). See the SAMS Linux Unleashed series books (Red Hat and Slackware) for detailed information.
  • Solaris--major--Sun Microsystems' version with a strong hardware presence in the marketplace and a strong future growth path.
  • SunOs--minor--Largely being superseded by Solaris installations. A good variant, but it is difficult for a company to support two versions of UNIX at a time.
  • SVR4--major--This version has a strong presence in the marketplace. In addition, many variants can trace their heritage to System V Release 4.
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The most commonly used UNIX variants, including:

  • HP-UX (Hewlett Packard)
  • Solaris (SunSoft)
  • SVR4 (AT&T)
  • AIX (IBM)
  • BSD (Berkeley Software)
  • Linux
  • SunOS (predecessor to Solaris)
  • IRIX

47-Basic UNIX Commands

Basic Unix Commands

1.ls -l for listing the files as well as directories those
are kept in the particular working directory

syntax: #ls -l

2.ls -la same as 'ls -l'but by this command we can also see
the hiden files.

syntax: #ls -la

3.ls -li same as 'ls -la' but it will also shows us the inode
number of each and every file

syntax: #ls -li

4.ls by this command we can see only file name nothing
else 

syntax: #ls

5.clear it will clear the screen(short cut ctl+l)

syntax: #clear

6.exit to end a current session as well current terminal
logging

syntax:$exit

7.touch to create a new empty file

syntax: $touch

8.cd to change the working/present directory

syntax: $cd /home/mango
where '/home/mango' is the desired directory to be
change from '/root'

9.cat to view the contents of a file and it is also used for creating a new file with some contents

syntax: $cat to view
file contents
$cat > newfilename
enter,then you can write something in the file and
then to save the file contents press clt+d then enter
10.mkdir to make a new directory

syntax: $mkdir newdirname
you can also create a directory at your desired path without changing your present working directory

syntax: $mkdir /home/mango/newdirname

11.rm to remove a empty file

syntax: $rm filename

12.rmdir to remove a empty directory

syntax: $rmdir directoryname

13.rm [-i/-r/-f] to remove a directory with its subdirectories as well as its files that is to remove a directory which already contains some files in it

syntax: $rm –i directory/filename

-i stands for interactively
-r stands for recursively
-f stands for forcefully

14.cp to copy something in a destination file or directory

syntax: $cp sourcepath destinationpath
example: $cp /home/mango/webmin.rpm   /root/abcd
in this example the webmin.rpm file will be copied in /root/abcd directory

15.mv to move one file or directory from one place to another place, it is also used for renaming adirectory or file

syntax: $mv source destination
$mv oldfilename newfilename [to change the file name]

16.man to view the mannual page of commands for syntax
syntax: $man commandname

17.info to view the information about any command

syntax: $mkdir info

18.--help to view the help doccuments of a command

syntax: $commandname --help

19.dir to view the subdirectories and files under the directory

syntax: $dir

20.su - to become a super user

syntax: [mango@localhost mango]$su -
output wil be [root@localhost root#]

21.who by this command you can see the user name and their ip addresses who have logged in on your server

syntax: $who

22.whoami this command shows your current logged in terminal user name

syntax: $whoami

23.who am i this command shows you the logged in terminal number and user name and more detailed information

syntax: $who am i

24.pwd to view the present working directory

syntax: $pwd

25.rpm -ivh to install a rpm package

syntax: $rpm –ivh packagename.rpm

rpm stands for 'redhat package manager'
-i stands for install
-v stands for verbose mode
-h stands for with hash sign(#)

26.rpm -q to query about any rpm package

syntax: $rpm -q package name

27.rpm -e to uninstall a rpm package

syntax: $rpm -e package

28.find / -name to find any file or directory in linux file system

syntax: $find / -name filename

29.su username to switch from one user to another users home directory

syntax: $su mango
output will be [mango@localhost root]#cd [mango@localhost mango]#

30.su - username to switch from one user to another user users home directory directly

syntax: $su - mango

31.useradd to create a new user

syntax: $useradd username

32.passwd to give a password of a user

syntax: $passwd madhava
output will be give a password for user madhava:(here you have to type a password for madhava user) confirm password:(again type the same password)

33.userdel to remove a user from linux
syntax: $userdel tarun

34.groupadd to add a new group

syntax: $groupadd groupname

35.gruopdel to delete a group

syntax: $groupdel groupname

36.chown to change the ownership of a file or directory

syntax: $chown ownername filename
example:$ls -l
output:
drwxrw-rw- 2 root root 4096 Mar 11 12:03 abcd
(permission) (own) (group own)(size) (name)

$chown tarun /abcd
in this example /abcd directory owner will be change to madhava user effect

$ls -l
drwxrw-rw- 2 madhava root 4096 Mar 11 12:03 abcd

37.chgrp to change the group ownership of a file or directory

syntax: $chgrp newgroupownername filename
example:$ls -l
drwxrw-rw- 2 madhava root 4096 Mar 11 12:03 abcd

$chgrp madhava /abcd
effect:$ls -l
drwxrw-rw- 2 madhava madhava 4096 Mar 11 12:03 abcd

38.chmod to change the permission of a file or directory

drwxrw-rw- 2 root root 4096 Mar 11 12:03 abcd
(permission) (ownr) (grpownr) (size) (name) IN

OCTAL VALUE:d stands for directiry READ=4
r stands for read only permission WRITE=2
w stands for write only permission
EXECUTE=1
x stands for execute only permission

drwxrw-rw- FIRST OCTET FOR DENOTING THE DIRECTORY OR FILE OR LINK FILE ETC.

SECOND THREE OCTET FOR USER OR OWNER PERMISSION (rwx OR 7 IN OCTAL VALUE) THIRD THREE OCTET FOR GROUP PERMISSION (rw- OR 6 IN OCTAL VALUE)
FORTH THREE OCTET FOR OTHERS PERMISSION (rw- OR 6 IN OCTAL VALUE)

SYNTAX: $chmod value fileordirectoryname
example: $ls -l

drwxrw-rw- 2 madhava root 4096 Mar 11 12:03 abcd

$chmod 402 /abcd
$ls -l
drw-----w- 2 madhava madhava 4096 Mar 11 12:03 abcd

40.usermod to modify the user profile

synatx: [root@localhost root]#usermod –parameter groupname username 

41.vi to edit a file.

synatx: $vi filename/absolute_path/relative_path 

42.ipconfig to get information about Ethernet card (for WINDOWS).

synatx: $ipconfig /all 

43.ifconfig to get information about Ethernet card (for LINUX).

synatx: $ifconfig 

44.ping to check whether two machines are connected or not.

synatx: $ping 

45.telnet to login to the server(in which LINUX operating system is running) from a remote machine.

synatx: $telnet

46.init to change the Run Level.

synatx: $init run_level
run_level: 0 --> halt (Do NOT set initdefault to this)
1 --> Single user mode 
2 --> Multiuser, without NFS(The same as 3,
if you do not have networking)
3 --> full multiuser mode
4 --> unused
5 --> for graphics mode(X11)
6 --> reboot (Do NOT set init default to this) 

47.shutdown to halt/restart the machine

syntax: $shutdown -h/-r time
-h --> for halt
-r --> for restart 

UNIX commands


Unix commands
man,banner,cal, calendar,clear,nohup, tty .
Manual command.
man man This is help command, and will explains you about online manual pages you can also use man in conjunction with any command to learn more about that command for example. 
  • man ls will explain about the ls command and how you can use it.
  • man -k pattern command will search for the pattern in given command.

Banner command.
banner prints characters in a sort of ascii art poster, for example to print wait in big letters. I will type 
banner wait at unix command line or in my script. This is how it will look.

  
 #    #    ##       #     #####
 #    #   #  #      #       #
 #    #  #    #     #       #
 # ## #  ######     #       #
 ##  ##  #    #     #       #
 #    #  #    #     #       #
 

Cal command 
cal command will print the calander on current month by default. If you want to print calander of august of 1965. That's eightht month of 1965. 
cal 8 1965 will print following results.

    August 1965
 S  M Tu  W Th  F  S
 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
 

Clear command
clear command clears the screen and puts cursor at beginning of first line.

Calendar command 
calendar command reads your calendar file and displays only lines with current day. 
For example in your calendar file if you have this

12/20   Test new software.
1/15    Test newly developed 3270 product.
1/20    Install memory on HP 9000 machine.
On dec 20th the first line will be displayed. you can use this command with your crontab file or in your login files.

Nohup command. 
nohup command if added in front of any command will continue running the command or process even if you shut down your terminal or close your session to machine. For exmaple, if I want to run a job that takes lot of time and must be run from terminal and is called update_entries_tonight . 
nohup update_entries_tonight will run the job even if terminal is shut down in middle of this job. 


Tty command 
Tty command will display your terminal. Syntax is
tty options

Options
  • -l will print the synchronous line number.
  • -s will return only the codes: 0 (a terminal), 1 (not a terminal), 2 (invalid options) (good for scripts)


cat,cd, cp, file,head,tail, ln,ls,mkdir ,more,mv, pwd, rcp,rm, rmdir, wc.

Pwd command. 
pwd command will print your home directory on screen, pwd means print working directory.

 /u0/ssb/sandeep
is output for the command when I use pwd in /u0/ssb/sandeep directory.

Ls command 
ls command is most widely used command and it displays the contents of directory. 
options
  • ls will list all the files in your home directory, this command has many options.
  • ls -l will list all the file names, permissions, group, etc in long format.
  • ls -a will list all the files including hidden files that start with . .
  • ls -lt will list all files names based on the time of creation, newer files bring first.
  • ls -Fxwill list files and directory names will be followed by slash.
  • ls -Rwill lists all the files and files in the all the directories, recursively.
  • ls -R | more will list all the files and files in all the directories, one page at a time.

Mkdir command. 
mkdir sandeep will create new directory, i.e. here sandeep directory is created.


Cd command. 
cd sandeep will change directory from current directory to sandeep directory. 
Use pwd to check your current directory and ls to see if sandeep directory is there or not. 
You can then use cd sandeep to change the directory to this new directory.


  find . -depth -print | cpio -padm /mydir will move a directory tree.

Dump command is useful to backup the file systems. 
dump command copies all the files in filesystem that have been changed after a certain date. It is good for incremental backups. This information about date is derived from /var/adm/dumpdates and /etc/fstab . 
syntax for HP-UX dump is 
/usr/sbin/dump [option [argument ...] filesystem] 

Options
  • 0-9 This number is dump level. 0 option causes entire filesystem to be dumped.
  • b blocking factor taken into argument.
  • d density of tape default value is 1600.
  • f place the dump on next argument file instead of tape.
  • This example causes the entire file system (/mnt) to be dumped on /dev/rmt/c0t0d0BEST and specifies that the density of the tape is 6250 BPI.
    • /usr/sbin/dump 0df 6250 /dev/rmt/c0t0d0BEST /mnt
  • for more info type man dump at command line.

Pack command. 
pack command compacts each file and combine them together into a filename.z file. The original file is replaced. Pcat and unpack will restore packed files to their original form. 
Syntax is 
Pack options files 

Options
  • - Print number of times each byte is used, relative frequency and byte code.
  • -f Force the pack even when disk space isn't saved.
  • To display Packed files in a file use pcat command 
    pcat filename.z
  • To unpack a packed file use unpack command as unpack filename.z .

Tar command. 
tar command creates an archive of files into a single file.
Tar copies and restore files to a tape or any storage media. Synopsis of tar is
tar [options] [file]

Examples:
tar cvf /dev/rmt/0 /bin /usr/bin creates an archive of /bin and /usr/bin, and store on the tape in /dev/rmt0. 
tar tvf /dev/rmt0 will list the tape's content in a /dev/rmt0 drive. 
tar cvf - 'find . -print' > backup.tar will creates an archive of current directory and store it in file backup.tar.

Functions:
  • c creates a new tape.
  • r append files to a tape.
  • t print the names of files if they are stored on the tape.
  • x extract files from tape.
Options:
  • b n use blocking factor of n.
  • l print error messages about links not found.
  • L follow symbolic links.
  • v print function letter (x for extraction or a for archive) and name of files.

Mt command is used for tape and other device functions like rewinding, ejecting, etc. It give commands to tape device rather than tape itself. Mt command is BSD command and is seldom found in system V unix versions. 
syntax is 
mt [-t tapename] command [count] 

mt for HP-UX accept following commands
  • eof write count EOF marks.
  • fsf Forward space count files.
  • fsr Forward space count records.
  • bsf Backward space count files.
  • bsr Backward space count records.
  • rew Rewind tape.
  • offl Rewind tape and go offline.
  • eod Seek to end of data (DDS and QIC drives only).
  • smk Write count setmarks (DDS drives only).
  • fss Forward space count setmarks (DDS drives only).
  • bss Backward space count setmarks (DDS drives only).
  • Examples
    • mt -t /dev/rmt/0mnb rew will rewind the tape in this device.
    • mt -t /dev/rmt/0mnb offl will eject the tape in this device.

diff,dircmp, cmp, grep, find.

Diff command. 
diff command will compare the two files and print out the differences between. 
Here I have two ascii text files. fileone and file two. 
Contents of fileone are

This is first file 
this is second line
this is third line
this is different    as;lkdjf 
this is not different

filetwo contains
This is first file
this is second line
this is third line
this is different    xxxxxxxas;lkdjf
this is not different

diff fileone filetwo will give following output
 4c4
< this is different    as;lkdjf
---
> this is different    xxxxxxxas;lkdjf

Cmp command. 
cmp command compares the two files. For exmaple I have two different files fileone and filetwo. 
cmp fileone filetwo will give me

fileone filetwo differ: char 80, line 4 

if I run cmp command on similar files nothing is returned.
-s command can be used to return exit codes. i.e. return 0 if files are identical, 1 if files are different, 2 if files are inaccessible. 
This following command prints a message 'no changes' if files are same 
cmp -s fileone file1 && echo 'no changes' .
no changes

Dircmp Command. 
dircmp command compares two directories. If i have two directories in my home directory named
dirone and dirtwo and each has 5-10 files in it. Then 
dircmp dirone dirtwo will return this

 Dec  9 16:06 1997  dirone only and dirtwo only Page 1
 
./cal.txt                                   ./fourth.txt
./dohazaar.txt                              ./rmt.txt
./four.txt                                  ./te.txt
./junk.txt                                  ./third.txt
./test.txt 

Grep Command 
grep command is the most useful search command. You can use it to find processes running on system, to find a pattern in a file, etc. It can be used to search one or more files to match an expression. 
It can also be used in conjunction with other commands as in this following example, output of ps command is passed to grep command, here it means search all processes in system and find the pattern sleep. 
ps -ef | grep sleep will display all the sleep processes running in the system as follows.

     ops 12964 25853  0 16:12:24 ttyAE/AAES  0:00 sleep 60
     dxi 12974 15640  0 16:12:25 ttyAH/AAHP  0:00 sleep 60
     ops 12941 25688  0 16:12:21 ttyAE/AAEt  0:00 sleep 60
     ops 12847 25812  0 16:11:59 ttyAH/AAH6  0:00 sleep 60
     ops 12894 25834  0 16:12:12 ttyAE/AAEX  0:00 sleep 60
     dxi 13067 27253  2 16:12:48 ttyAE/ABEY  0:00 sleep 1
     ops 13046 25761  0 16:12:44 ttyAE/AAE0  0:00 sleep 60
     dxi 12956 13078  0 16:12:23 ttyAG/AAG+  0:00 sleep 60
     ops 12965 25737  0 16:12:24 ttyAE/AAEp  0:00 sleep 60
     ops 12989 25778  0 16:12:28 ttyAH/AAHv  0:00 sleep 60
     ssb 13069 26758  2 16:12:49 ttyAH/AAHs  0:00 grep sleep
     pjk 27049  3353  0 15:20:23 ?           0:00 sleep 3600
Options:
  • -b option will precede each line with its block number.
  • -c option will only print the count of matched lines.
  • -i ignores uppercase and lowercase distinctions.
  • -l lists filenames but not matched lines.
other associated commands with grep are egrep and fgrep. egrep typically runs faster. for more information type man egrep or man fgrep in your system.

Find command. 
Find command is a extremely useful command. you can search for any file anywhere using this command provided that file and directory you are searching has read write attributes set to you ,your, group or all. Find descends directory tree beginning at each pathname and finds the files that meet the specified conditions. Here are some examples.

Some Examples: 
find $HOME -print will lists all files in your home directory. 
find /work -name chapter1 -print will list all files named chapter1 in /work directory. 
find / -type d -name 'man*' -print will list all manpage directories. 
find / -size 0 -ok rm {} \; will remove all empty files on system.

conditions of find
  • -atime +n |-n| n will find files that were last accessed more than n or less than -n days or n days.
  • -ctime +n or -n will find that were changed +n -n or n days ago.
  • -depth descend the directory structure, working on actual files first and then directories. You can use it with cpio command.
  • -exec commad {} \; run the Unix command on each file matched by find. Very useful condition.
  • -print print or list to standard output (screen).
  • -name pattern find the pattern.
  • -perm nnnfind files whole permission flags match octal number nnn.
  • -size n find files that contain n blocks.
  • -type c Find file whole type is c. C could be b or block, c Character special file, d directory, p fifo or named pipe, l symbolic link, or f plain file.

cut,paste, sort, uniq,awk,sed,vi.

Cut command. 
cut command selects a list of columns or fields from one or more files.
Option -c is for columns and -f for fields. It is entered as 
cut options [files] 
for example if a file named testfile contains

this is firstline
this is secondline
this is thirdline
Examples: 
cut -c1,4 testfile will print this to standard output (screen)
ts
ts
ts
It is printing columns 1 and 4 of this file which contains t and s (part of this).
Options:
  • -c list cut the column positions identified in list.
  • -f list will cut the fields identified in list.
  • -s could be used with -f to suppress lines without delimiters.

Paste Command. 
paste command merge the lines of one or more files into vertical columns separated by a tab. 
for example if a file named testfile contains

this is firstline
and a file named testfile2 contains
this is testfile2
then running this command 
paste testfile testfile2 > outputfile
will put this into outputfile
this is firstline       this is testfile2 
it contains contents of both files in columns.
who | paste - - will list users in two columns.
Options:
  • -d'char' separate columns with char instead of a tab.
  • -s merge subsequent lines from one file.

Sort command. 
sort command sort the lines of a file or files, in alphabetical order. for example if you have a file named testfile with these contents

zzz
aaa
1234
yuer
wer
qww
wwe
Then running 
sort testfile 
will give us output of
1234
aaa
qww
wer
wwe
yuer
zzz
Options:
  • -b ignores leading spaces and tabs.
  • -c checks whether files are already sorted.
  • -d ignores punctuation.
  • -i ignores non-printing characters.
  • -n sorts in arithmetic order.
  • -ofile put output in a file.
  • +m[-m] skips n fields before sorting, and sort upto field position m.
  • -r reverse the order of sort.
  • -u identical lines in input file apear only one time in output.

Uniq command. 
uniq command removes duplicate adjacent lines from sorted file while sending one copy of each second file. 
Examples

sort names | uniq -d will show which lines appear more than once in names file.

Options:
  • -c print each line once, counting instances of each.
  • -d print duplicate lines once, but no unique lines.
  • -u print only unique lines.

Awk and Nawk command. 
awk is more like a scripting language builtin on all unix systems. Although mostly used for text processing, etc. 
Here are some examples which are connected with other commands. 
Examples:
df -t | awk 'BEGIN {tot=0} $2 == "total" {tot=tot+$1} END {print (tot*512)/1000000}' Will give total space in your system in megabytes. 
Here the output of command df -t is being passed into awk which is counting the field 1 after pattern "total" appears. Same way if you change $1 to $4 it will accumulate and display the addition of field 4 
which is used space. 
for more information about awk and nawk command in your system enter man awk or man nawk.


Sed command. 
sed command launches a stream line editor which you can use at command line. 
you can enter your sed commands in a file and then using -f option edit your text file. It works as 
sed [options] files 

options:
  • -e 'instruction' Apply the editing instruction to the files.
  • -f script Apply the set of instructions from the editing script.
  • -n suppress default output.

for more information about sed, enter man sed at command line in your system.

Vi editor. 
vi command launches a vi sual editor. To edit a file type 
vi filename
vi editor is a default editor of all Unix systems. It has several modes. In order to write characters you will need to hit i to be in insert mode and then start typing. Make sure that your terminal has correct settings, vt100 emulation works good if you are logged in using pc. 
Once you are done typing then to be in command mode where you can write/search/ you need to hit :w filename to write 
and in case you are done writing and want to exit 
:w! will write and exit. 


options:
  • i for insert mode.
    • I inserts text at the curson
    • A appends text at the end of the line.
    • a appends text after cursor.
    • O open a new line of text above the curson.
    • o open a new line of text below the curson.
  • : for command mode.
    • <escape> to invoke command mode from insert mode.
    • :!sh to run unix commands.
    • x to delete a single character.
    • dd to delete an entire line
    • ndd to delete n number of lines.
    • d$ to delete from cursor to end of line.
    • yy to copy a line to buffer.
    • P to paste text from buffer.
    • nyy copy n number of lines to buffer.
    • :%s/stringA/stringb /g to replace stringA with stringB in whole file.
    • G to go to last line in file.
    • 1G to go to the first line in file.
    • w to move forward to next word.
    • b to move backwards to next word.
    • $ to move to the end of line.
    • J join a line with the one below it.
  • /string to search string in file.
  • n to search for next occurence of string.


Shell programming is integral part of Unix operating systems. Shell is command line userinterface to Unix operating system, User have an option of picking an interface on Unix such as ksh, csh, or default sh., these are called shells(interface). Shell programming is used to automate many tasks. Shell programming is not a programming language in the truest sense of word since it is not compiled but rather an interpreted language. Unix was written in C language and thus c language is integral part of unix and available on all versions. Shells, like ksh and csh are popular shells on unix although there are 5 or 6 different shells available but I will only be discussing ksh and csh as well as sh. Common features among all shells are job control, for example if I am running a processes which is searching the whole system for .Z files and output is directed to a file named compressedfiles.
example:
  • find / -name *.Z -print > compressedfiles 
    then after entering this command hitting
  • <control z> 
    key will suspend this job, then entering
  • bg 
    at command line will put this job in background, entering
  • fg
    will put this job in foreground. Entering
  • jobs 
    at command line will show me all my concurrent jobs that are running.
Other common features
    • > will redirect output from standard out (screen) to file or printer or whatever you like.
    • >> filename will append at the end of a file called filename.
    • < will redirect input to a process or commnand.
    • | pipe output, or redirect output, good for joining commands, i.e. find command with cpio, etc.
    • & at the end of command will run command in background.
    • ; will separate commands on same line.
    • * will match any characters in a file or directories. junk* will match all files with first 4 letters
    • ? will match single characters in a file.
    • [] will match any characters enclosed.
    • () execute in subshell.
    • ` ` to run a command inside another command and use its output.
    • " " partial quote for variables.
    • ' ' full quote for variables.
    • # begin comment (if #/bin/ksh or csh or sh is entered at first line of script it runs script in that shell)
    • bg background execution.
    • break break from loop statements.
    • continue Resume a program loop.
    • Kill pid number will terminate running jobs
    • stop will stop background job.
    • suspend will suspend foreground job.
    • wait will wait for a background job to finish.

Bourne Shell (sh shell). 
sh or Bourne shell is default shell of Unix operating systems and is the most simplest shell in Unix systems. 

Examples:
  • cd; ls execute one after another.
  • (date;who;pwd)> logifile will redirect all the output from three commands to a filenamed logfile.
  • sort file | lp will first sort a file and then print it.
  • alias [options] [name[='command']] will let you create your own commands. i.e.
    • alias ll="ls -la" will execute `ls -la` command whenever ll is entered.
  • let expressions is syntax of let statement.
    • let i=i+1 will work as a counter with i incrementing each time this statement is encountered.
  • for x[in list] do commands done is syntax for for do loop.
  • function name {commands;} is the syntax of a function which can be called from anywhere in program.
  • if condition1 then commands1 elif condition2 then commands2 ... ... ... else commands3 fi

Ksh shell (Korn). 
Ksh or Korn shell is widely used shell.


Csh or C shell 
csh is second most used shell.


Echo command 
echo command in shell programming.


Line command. 
line command in shell programming.


Sleep command. 
sleep command in shell programming.


Test Command. 
test command in shell programming.


CC compiler (c programming language compiler). 
Since Unix is itself written in C programming language, most Unix operating systems come with c compiler called cc.




Cu command. 
cu command is used for communications over a modem or direct line with another Unix system. 
Syntax is 
cu options destination

Options
  • -bn process lines using n-bit characters (7 or 8).
  • -cname Search UUCP's device file and select local area network that matches name.
  • -d Prints diagnostics.
  • -e sends even parity data to remote system
  • -lline communicate on this device (line=/dev/tty001, etc)
  • -n prompts for a telephone number.
  • -sn set transmission rate to n(e.g 1200,2400,9600, BPS)
Destination
  • telno is the telephone number of the modem to connect to.
  • system is call the system known to uucp.
  • aadr is an address specific to LAN.

Ftp command (protocol). 
ftp command is used to execute ftp protocol using which files are transferred over two systems.
Syntax is 
ftp options hostname

options
  • -d enable debugging.
  • -g disable filename globbing.
  • -i turn off interactive prompts.
  • -v verbose on. show all responses from remote server.
ftp hostname by default will connect you to the system, you must have a login id to be able to transfer the files. Two types of files can be transferred, ASCII or Binary. bin at ftp> prompt will set the transfer to binary. Practice FTP by ftping to nic.funet.fi loggin in as anomymous with password being your e-mail address.

Login command. 
login command invokes a login session to a Unix system, which then authenticates the login to a system. System prompts you to enter userid and password.


Rlogin command. 
rlogin command is used to log on to remote Unix systems, user must have permissions on both systems as well as same userid, or an id defined in .rhosts file. Syntax is 
rlogin options host

options
  • -8 will allow 8 bit data to pass, instead of 7-bit data.
  • -e c will let you use escape character c.
  • -l user will let you to login as user to remote host, instead of same as local host.

Talk command. 
talk command is used to invoke talk program available on all unix system which lets two users exchange information back and forth in real time. Syntax is 
talk userid@hostname 


Telnet command. 
Telnet command invokes a telnet protocol which lets you log on to different unix, vms or any machine connected over TCP/IP protocol, IPx protocol or otherwise. Syntax is 
telnet hostname 


Vacation command. 
vacation command is used when you are out of office. It returns a mail message to sender announcing that you are on vacation. to disable this feature, type mail -F " " . 
syntax is 
vacation options

Options
  • -d will append the date to the logfile.
  • -F user will forward mail to user when unable to send mail to mailfile.
  • -l logfile will record in the logfile the names of senders who received automatic reply.
  • -m mailfile will save received messages in mailfile.

Write command will initiate an interactive conversation with user. Syntax is 
write user tty 




Compress command. 
Compress command compresses a file and returns the original file with .z extension, to uncompress this filename.Z file use uncompress filename command. syntax for compress command is 
compress options files

Options
  • -bn limit the number of bits in coding to n.
  • -c write to standard output (do not change files).
  • -f compress conditionally, do not prompt before overwriting files.
  • -v Print the resulting percentage of reduction for files.

Uncompress command. 
Uncompress file uncompresses a file and return it to its original form. 
syntax is 
uncompress filename.Z this uncompresses the compressed file to its original name.

Options
  • -c write to standard output without changing files

Cpio command. 
cpio command is useful to backup the file systems. It copy file archives in from or out to tape or disk, or to another location on the local machine. Its syntax is 
cpio flags [options]

It has three flags, -i, -o, -p
  • cpio -i [options] [patterns]
    • cpio -i copy in files who names match selected patterns.
    • If no pattern is used all files are copied in.
    • It is used to write to a tape.
cpio -o
    • Copy out a list of files whose name are given on standard output.
cpio -p
    • copy files to another directory on the same system.
Options
    • -a reset access times of input files.
    • -A append files to an archive (must use with -o).
    • -b swap bytes and half-words. Words are 4 bytes.
    • -B block input or output using 5120 bytes per record.
    • -c Read or write header information as Ascii character.
    • -d create directories as needed.
    • -l link files instead of copying.
    • -o file direct output to a file.
    • -r rename files interactively.
    • -R ID reassign file ownership and group information to the user's login ID.
    • -V print a dot for each file read or written.
    • -s swap bytes.
    • -S swap half bytes.
    • -v print a list of filenames.
Examples
    • find . -name "*.old" -print | cpio -ocvB > /dev/rst8 will backup all *.old files to a tape in /dev/rst8
    • cpio -icdv "save"" < /dev/rst8 will restore all files whose name contain "save"
    • find . -depth -print | cpio -padm /mydir will move a directory tree.

Dump command is useful to backup the file systems. 
dump command copies all the files in filesystem that have been changed after a certain date. It is good for incremental backups. This information about date is derived from /var/adm/dumpdates and /etc/fstab . 
syntax for HP-UX dump is 
/usr/sbin/dump [option [argument ...] filesystem] 

Options
  • 0-9 This number is dump level. 0 option causes entire filesystem to be dumped.
  • b blocking factor taken into argument.
  • d density of tape default value is 1600.
  • f place the dump on next argument file instead of tape.
  • This example causes the entire file system (/mnt) to be dumped on /dev/rmt/c0t0d0BEST and specifies that the density of the tape is 6250 BPI.
    • /usr/sbin/dump 0df 6250 /dev/rmt/c0t0d0BEST /mnt
  • for more info type man dump at command line.

Pack command. 
pack command compacts each file and combine them together into a filename.z file. The original file is replaced. Pcat and unpack will restore packed files to their original form. 
Syntax is 
Pack options files 

Options
  • - Print number of times each byte is used, relative frequency and byte code.
  • -f Force the pack even when disk space isn't saved.
  • To display Packed files in a file use pcat command 
    pcat filename.z
  • To unpack a packed file use unpack command as unpack filename.z .

Tar command. 
tar command creates an archive of files into a single file.
Tar copies and restore files to a tape or any storage media. Synopsis of tar is
tar [options] [file]

Examples:
tar cvf /dev/rmt/0 /bin /usr/bin creates an archive of /bin and /usr/bin, and store on the tape in /dev/rmt0. 
tar tvf /dev/rmt0 will list the tape's content in a /dev/rmt0 drive. 
tar cvf - 'find . -print' > backup.tar will creates an archive of current directory and store it in file backup.tar.

Functions:
  • c creates a new tape.
  • r append files to a tape.
  • t print the names of files if they are stored on the tape.
  • x extract files from tape.
Options:
  • b n use blocking factor of n.
  • l print error messages about links not found.
  • L follow symbolic links.
  • v print function letter (x for extraction or a for archive) and name of files.


Mt command
Mt command is used for tape and other device functions like rewinding, ejecting, etc. It give commands to tape device rather than tape itself. Mt command is BSD command and is seldom found in system V unix versions. 
syntax is 
mt [-t tapename] command [count] 

mt for HP-UX accept following commands
  • eof write count EOF marks.
  • fsf Forward space count files.
  • fsr Forward space count records.
  • bsf Backward space count files.
  • bsr Backward space count records.
  • rew Rewind tape.
  • offl Rewind tape and go offline.
  • eod Seek to end of data (DDS and QIC drives only).
  • smk Write count setmarks (DDS drives only).
  • fss Forward space count setmarks (DDS drives only).
  • bss Backward space count setmarks (DDS drives only).
  • Examples
    • mt -t /dev/rmt/0mnb rew will rewind the tape in this device.
    • mt -t /dev/rmt/0mnb offl will eject the tape in this device.


at, chmod,chgrp, chown,crontab,date, df,du, env, finger, ps,ruptime, shutdwon,stty, who.

At command. 
at command along with crontab command is used to schedule jobs. 
at options time [ddate] [+increment] is syntax of at command.
for example if I have a script named usersloggedin which contains.

 #!/bin/ksh
who | wc -l
echo "are total number of people logged in at this time."
and I want to run this script at 8:00 AM. So I will first type at 8:00 %lt;enter>
usersloggedin %lt;enter>
I will get following output at 8:00 AM
      30
are total number of people logged in at this time.
Options:
  • -f file will execute commands in a file.
  • -m will send mail to user after job is completed.
  • -l will report all jobs that are scheduled and their jobnumbers.
  • -r jobnumber will remove specified jobs that were previously scheduled.

Chmod command. 
chmod command is used to change permissions on a file. 
for example if I have a text file with calender in it called cal.txt.
initially when this file will be created the permissions for this file depends upon umask set in your profile files. As you can see this file has 666 or -rw-rw-rw attributes. 

ls -la cal.txt

-rw-rw-rw-    1 ssb      dxidev       135 Dec  3 16:14 cal.txt
In this line above I have -rw-rw-rw- meaning respectively that owner can read and write file, member of the owner's group can read and write this file and anyone else connected to this system can read and write this file., next ssb is owner of this file dxidev is the group of this file, there are 135 bytes in this file, this file was created on December 3 at time16:14 and at the end there is name of this file. Learn to read these permissions in binary, like this for example Decimal 644 which is 110 100 100 in binary meand rw-r--r-- or user can read,write this file, group can read only, everyone else can read only. Similarly, if permissions are 755 or 111 101 101 that means rwxr-xr-x or user can read, write and execute, group can read and execute, everyone else can read and execute. All directories have d in front of permissions. So if you don't want anyone to see your files or to do anything with it use chmod command and make permissions so that only you can read and write to that file, i.e. 
chmod 600 filename.


Chgrp command. 
chgrp command is used to change the group of a file or directory. 
You must own the file or be a superuser. 
chgrp [options] newgroup files is syntax of chgrp. 
Newgroup is either a group Id or a group name located in /etc/group .

Options:
  • -h will change the group on symbolic links.
  • -R recursively descend through directory changing group of all files and subdirectories.

Chown command. 
chown command to change ownership of a file or directory to one or more users.
Syntax is 
chown options newowner files

Options
  • -h will change the owner on symbolic links.
  • -R will recursively descend through the directory, including subdirectories and symbolic links.

Crontab command. 
crontab command is used to schedule jobs. You must have permission to run this command by unix Administrator. Jobs are scheduled in five numbers, as follows.

 Minutes                                0-59
 Hour                     0-23
 Day of month       1-31
 month                   1-12
 Day of week         0-6 (0 is sunday) 
so for example you want to schedule a job which runs from script named backup_jobs in /usr/local/bin directory on sunday (day 0) at 11.25 (22:25) on 15th of month. The entry in crontab file will be. * represents all values.
 25 22  15 * 0 /usr/local/bin/backup_jobs 
The * here tells system to run this each month. 
Syntax is 
crontab file So a create a file with the scheduled jobs as above and then type
crontab filename .This will scheduled the jobs.

Date command. 
Date displays todays date, to use it type date at prompt. 

Sun Dec  7 14:23:08 EST 1997 
is similar to what you should see on screen.

Df command. 
df command displays information about mounted filesystems. It reports the number of free disk blocks. Typically a Disk block is 512 bytes (or 1/2 Kilobyte). 
syntax is 
df options name 

Options
  • -b will print only the number of free blocks.
  • -e will print only the number of free files.
  • -f will report free blocks but not free inodes.
  • -F type will report on an umounted file system specified by type.
  • -k will print allocation in kilobytes.
  • -l will report only on local file systems.
  • -n will print only the file system name type, with no arguments it lists type of all filesystems

Du command. 
du command displays disk usage.


Env command. 
env command displays all the variables.


Finger command. 
finger command.


PS command 
ps command is probably the most useful command for systems administrators. It reports information on active processes. 
ps options

options.
  • -a Lists all processes in system except processes not attached to terminals.
  • -e Lists all processes in system.
  • -f Lists a full listing.
  • -j print process group ID and session ID.

Ruptime command. 
ruptime command tells the status of local networked machines.
ruptime options

options.
  • -a include user even if they've been idle for more than one hour.
  • -l sort by load average.
  • -r reverse the sort order.
  • -t sort by uptime.
  • -i sort by number of users.

Shutdown command. 
Shutdown command can only be executed by root. To gracefully bring down a system, shutdown command is used. 

options.
  • -gn use a grace-period of n seconds (default is 60).
  • -ik tell the init command to place system in a state k.
    • s single-user state (default)
    • 0 shutdown for power-off.
    • 1 like s, but mount multi-user file systems.
    • 5 stop system, go to firmware mode.
    • 6 stop system then reboot.
  • -y suppress the default prompt for confirmation.

Stty command 
stty command sets terminal input output options for the current terminal. without options stty reports terminal settings. 
stty options modes < device

options
  • -a report all options.
  • -g report current settings.
Modes
  • 0 hang up phone.
  • n set terminal baud.
  • erase keyname, will change your keyname to be backspace key.

Who command 
who command displays information about the current status of system.
who options file 
Who as default prints login names of users currently logged in.

Options
  • -a use all options.
  • -b Report information about last reboot.
  • -d report expired processes.
  • -H print headings.
  • -p report previously spawned processes.
  • -u report terminal usage.