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$ who

raj   console  Nov 19 09:35

reena   tty01   Nov 19 09:40

priya   tty02    Nov 19 09:41 

$ who-Hu

NAME  LINE   TIME      IDLE          PID        COMMENTS

raj  console  Nov 19 09:35     #                   32 

reena   tty01   Nov 19 09:40    0:20          33 

priya   tty01   Nov 19 09:41    0:40          34

$ who am i

reena   tty01   Nov 1909:40

The command

$ nl cherry.txt

Gives output:

1                    Loveliest of trees, the cherry now

2                    Is hung with bloom along the bough,

3                    And stands about the woodland ride

4                    Wearing white for Eastertide.

It is also possible to start from a different number. The command:

$ nl-v 100 cherry.txt

Gives the output:

100 Loveliest of trees, the cherry now

101 Is hung with bloom along the bough,

102 And stands about the woodland ride

103 Wearing white for Eastertide.

Syntax:

touch [options] expression filename (s)

     Common Options:

-a  change the access time of the file (SVR4 only)

-c  don't create the file if it doesn't already exist

-f  force the touch, regardless of read/write permissions

-m change the modification time of the file (SVR4 only)

-t  time use the time specified, not the current time (SVR4 only)

$ touch emp.lst  Creates file if it doesn't exist

2. When touch is used without options but with expression, it changes both times. The expression consists of an eight-digit number using the format MMDDHHMM (month, day, hour and minute). Optionally, we can suffix a

two- or four-digit year string :

$ touch 03161430 emp.lst

$ ls –l   emp.lst

-rw-r--r-1  kumar metal  870 Mar 16 14:30 emp.lst

arp [-evn] [-H type] [-i if] -a [hostname]

arp [-v] [-i if] -d hostname (pub]

arp [-v] [-H type] [-i if]-s hostname hw_addr [temp]

arp [-v] [-H type] [-i if] -s hostname hw_addr [netmask nm] pub

arp [-v] [-H type] [-i if] - Ds hostname ifa [netmask nm] pub

arp [-vnD] [-H type] [-i if] -f [filename]

Description: Arp manipulates the kernel's ARP cache in various ways. The primary options are clearing an address mapping entry and manually setting up one. For debugging purposes, the arp program also allows a complete dump of the ARP cache.

Options:

-V, --verbose

Tell the user what is going on by being verbose.

-n, --numeric

shows numerical addresses instead of trying to determine symbolic host, port or user names.

-H type, -hw-type type, -t type

When setting or reading the ARP cache, this optional parameter tells arp which class of entries it should check for. The default value of this parameter is ether (ie. hardware code 0x01 for IEEE 802.3 10Mbps Ethernet). Other values might include network technologies such as ARCnet (arcnet) PROnet (pronet), AX.25 (ax25) and NET/ROM (netrom).

-a [hostname), --display [hostname]

Shows the entries of the specified hosts. If the hostname parameter is not used, all entries will be displayed. The entries will be displayed in alternate (BSD) style.

-d hostname, --delete hostname

Remove any entry for the specified host. This can be used if the indicated host is brought down, for example.

-D, -use-device

Use the interface ifa's hardware address.

-e

Shows the entries in default (Linux) style.

Tag

Description

useradd [options] LOGIN

useradd -D

useradd -D [options]

-c, -comment COMMENT

Any text string. It is generally a short description of the login, and is currently used as the field for the user's full name.

-b, -base-dir BASE_DIR

The default base directory for the system if –d dir is not specified. BASE_DIR is concatenated with the account name to define the home directory. If the -m option is not used,

BASE_DIR must exist.

-d, -home HOME DIR

The new user will be created using HOME DIR as the value for the user's login directory. The default is to append the LOGIN name to BASE_DIR and use that as the login directory name. The directory HOME_DIR does not have to exist but will not be created if it is missing.

-e, expiredate EXPIRE_DATE

The date on which the user account will be disabled. The date is specified in the format YYYY-MM-DD.

-f, -inactive INACTIVE

The number of days after a password expires until the account is permanently disabled. A value of 0 disables the account as soon as the password has expired, and a value of -1 disables the feature. The default value is -1.

-g, -gid GROUP

The group name or number of the user's initial login group. The group name must exist. A group number must refer to an already existing group, /etc/default/useradd.

Syntax:

Is [options] [argument]

Common Options: When no argument is used, the listing will be of the current directory. There are many useful options for the Is command. A listing of many of them follows. When using the command, string the desired options together preceded by "."

-a    lists all files, including those beginning with a dot (.)

-d    lists only names of directories, not the files in the directory

-F    indicates type of entry with a trailing symbol:

directories /

sockets =

symbolic links @

executables*

-g   displays Unix group assigned to the file, requires the -l option (BSD      only)-or on an SVR4 machine, e.g. Solaris, this option has the opposite effect

-L    if the file is a symbolic link, lists the information for the file or directory   the link references, not the information for the link itself.

-I long listing: lists the mode, link information, owner. size. last modification time). If the file is a symbolic link, an arrow (-->) precedes the pathname of the linked-to file.

The mode field is given by the -I option and consists of 10 characters. The first character is one of the following:

character if entry is a:

d directory

- plain file

b block-type special file

c character-type special file

1 symbolic link

s socket

The next 9 characters are in 3 sets of 3 characters each. They indicate the file access permissions: the first 3 characters refer to the permissions for the user, the next three for the users in the UNIX group assigned to the file, and the last 3 to the permissions for other users on the system.

Designations are as follows:

r read permission

w write permission

x execute permission

-no permission

There are a few less commonly used permission designations for special circumstances. These are explained in the man page for ls.

Examples:

(i)                To list the files in a directory:

$ ls

Demofiles frank  linda

(ii)              To list all files in a directory, including the hidden (dot) files try:

$ Is –a

..cshrc .history -plan .rhosts frank

...emacs .login .profile demofiles linda

(iii) To show the hidden files, but not the current directory) and (parent directory), use option -A.

(iv) To show all the files recursively, use -R option. When we do this from /, it shows all the unhidden files in the whole file system recursively.

$Is /etc/sysconfig/networking

devices profiles

$Is -R -R/etc/sysconfig/networking

/etc/sysconfig/networking:

devices profiles

/etc/sysconfig/networking/devices:

/etc/sysconfig/networking/profiles:

Default

/etc/sysconfig/networking/profiles/default:

(v) To get a long listing: 

$ Is-al

total 24

drwxr-sr-x  5  workshop  acs  512  Jun7 11:12             .

drwxr-xr-x  6  root   sys  512  May29 09:59         ..

-rw--------  1  workshop  acs  525  May20 21:29         .emacs

-rwxr-xr-x 1  workshop  acs  238  May 14 09:44        .login

-rw-r—r--  1  workshop  acs  273  May 22 23:53        .plan

-rwxr-xr-x 1  workshop  acs  413  May 14 09:36        .profile

drwx------- 3  workshop  acs  512  May 24 11:18     demofiles

drwx------- 2  workshop  acs  512  May 21 10:48  frank

drwx------- 3  workshop  acs  512  May 24 10:59  linda

Instead of doing the 'ls - and then the checking for the first character to determine the type of file. We can use -F which classifies the file with different special character for different kind of files.

$ ls -F

Desktop/ Documents/ Ubuntu-App@ firstfile Music/ Public/ Templates/

Thus in the above output

/-directory.

nothing - normal file.

@- link file.

*- Executable file

(vi) $ Is-d Displays only directories:

(vii) $ Is -r Displays files in reverse order.

(viii) $ Is -f Interprets each name as a directory, not a file.

Syntax :

$ pwd [option]

e.g., /home/frank/src

Option:

-L (logical)        Use PWD from environment, even if it contains symbolic links

-P (physical)       Avoid all symbolic links

-help         Display this help and exit

--version        Output version information and exit

If both -L' and'-P options are used, option 'L' is taken into priority. If no option is specified at the prompt pwd will avoid all symlinks, i.e., take option -P into

 account

(i) To display a message (like echo Sun Solaris).

(ii) To evaluate shell variables (like echo (SHELL)).

Originally, echo was an external command, but today all shells have echo built-in.

Syntax :

echo[option] [string]

Option :

-n  do not output the trailing newline

-e   enable interpretation of backslash escapes

-E   disable interpretation of backslash escapes (default)

--help  display this help and exit

--version  output version information and exit

\0NNN

the character whose ASCII code is NNN (octal)

\\

Backslash

\a

alert (BEL)

\b

Backspace

\c

suppress trailing newline

\f

form feed

\n

new line

\r

carriage return

\t

horizontal tab

\v

vertical tab

Find path_list selection_criteria action

This is how find operates:

(i)          First, it recursively examines all files in the directories specified in path_list.

(ii)        It then matches each file for one or more selection criteria."

(iii)     Finally, it takes some action on those selected files.

The path_list comprises one or more subdirectories separated by whitespace. It can also be a host of selection_criteria that we can use to match a file, and multiple actions to dispose of the file.

Example: As our first example, let's use find to locate all files named a.out (the executable file generated by the C compiler):

$ find / -name a.out –print

/home/kumar/scripts/a.out

/home/tiwary/scripts/reports/a.out

/home/sharma/a.out

The path list () indicates that the search should start from the root directory. Each file in the list is then matched against the selection criteria (-name a. out), which always consists of an expression in the form operator argument. If the expression matches the file (ie, the file has the name a. out), the file is selected. The third section specifics the action (-print) to be taken on the files; in this case, a simple display on the terminal. We can also use relative names (like .) in the path list, and find will then output a list of relative pathnames. When find is used to match a group of filenames with a wild-card pattern, the pattern should be quoted to prevent the shell from looking at it:

$ find.-name "*.c"-print  All files with extension .c

$ find.-name '[A-Z]*’-print     Single quotes will also do

The first command looks for all C program source files in the current directory tree. The second one searches for all files whose names begin with an uppercase letter

We must not forget to use the -print option because without it find on UNIX systems will look for files all right but won't print the list. The-name is not the only operator used in framing the selection criteria.

Locating a File by Inode Number (- inum): Use the -inum option to find all

filenames that have the same inode number:

$ find / -inum 13975 –print

Find: cannot read dir /usr/lost+found: Permission denied

/usr/bin/gzip

/usr/bin/gunzip

/usr/bin/gzcat    "Cats" a compressed file

There is possibility of same inode number for more than one file and find throws an error message when it can't change to a directory. Sometimes, there will be so many of them on our screen that we would find it difficult to spot the files that actually show up as find's output. To avoid these messages, simply redirect the standard error to /dev/null.

File Type and Permissions (-type and -perm): The -type option followed by the letter f, d or I selects files of the ordinary, directory and symbolic link type. Here's how we locate all directories of our home directory tree:

$ cd; find. - type d-print 2>/dev/null.   Shows the . also

./.netscape       Displays hidden directories also

./java_progs

./cjjrogs

./cjjrogs/include

./cj>rogs/lib

./shellscripts

./.ssh

The relative pathname find displays, but that's because the pathname itself was relative (.). Find also doesn't necessarily display an ASCII sorted list. The sequence in which files are displayed depends on the internal organization of the file system

The -perm option specifies the permissions to match. For instance, -perm 666 selects files having read and write permission for all categories of users. Such files are security hazards. We'll often want to use two options in combination to restrict the search to only directories:

$ find SOME -perm 777-type d-print

(i)                Find uses an AND condition (an implied -a operator between -perm and - type) to select directories that provide all access rights to everyone.

(ii)              It selects files only if both selection criteria (-perm and -type) are fulfilled.

Finding Unused Files (-mtime and-atlme): Files tend to build up incessantly on disk. Some of them remain unaccessed or unmodified for months even years. find's options can easily match a file's modification (-mtime) and access (-atime) times to select them, -mtime helps in backup operations by providing a list of those files that have been modified, say in less than 2 days:

$ find. -mtime -2-print

-2 here means less than 2 days. To select from the /home directory all files that have not been accessed for more than a year, a positive value has to be used with - atime:

$ find /home -atime +365 -print | mailx root

Because find uses standard output the list can be stored in a file or used to mail a message. Remember, +365 means greater than 365 days, -365 means less than 365 days. For specifying exactly 365, use 365.

The find Operators (!, -o and -a) : There are three operators that are commonly used with find. The ! operator is used before an option to negate its meaning. So, to selects C program files use:

$ find. ! -name ".c" -print

To look for both Shell and Perl scripts, use the-o operator which represents an OR condition. We need to use an escaped pair of parentheses here:

find /home \(-name "*.sh" -o -name "*.pl" \)-print

The (and) are special characters that are interpreted by the shell to group commands. The same characters are used by find to group expressions using the - o and -a operators, the reason why they need to be escaped.

$ more chap01  Press q to exit

We'll see the contents of chap01 on the screen, one page at a time. At the bottom of the screen, we'll also see the filename and percentage of the file that has been viewed:

--More- (17%)

More has a couple of internal commands that don't show up on the screen when we invoke them, the command used to exit more, is an internal command.

Navigation : Irrespective of version, more uses the spacebar to scroll forward a page at a time. We can also scroll by small and large increments of lines or screens. To move forward one page, use f or the spacebar and to move back one page, use b.

The use of Repeat Factor: As a command prefix simply repeats the command that number of times. This means we can use 10f for scrolling forward by 10 pages and 30b for scrolling back 30 pages. Just ember that the commands themselves are not displayed on the screen-even for a moment.

Searching for a Pattern: We can perform a search for a pattern with the / command followed by the string. For instance, to look for the first while loop in our program, we'll have to enter this:

/while  Press (Enter] also

We can repeat this search for viewing the next whileloop section by pressing n, and we can do that repeatedly until we have scanned the entire file. Move back with b (using a repeat factor, if necessary) to arrive at the first page.

Internal commands:

Spacebar of f one page forward

10f   10 page forward

Enter key   one line forward

B    one page back

10b   10 page back

:n    next file

:P    previous file

.(Dot)    repeat last command

q    Quit

Syntax:

yacc - options grammar

Examples:

The following command:

$ yacc grammar.y

It draws yacc rules from the grammar.y file, and places the output in y.tab.c. We must compile the output file, y.tab.c, with a C language compiler to produce a yyparse function

(i) rw-rw-rw- (octal 666) for regular files.

(ii) rwxrwxrwx (octal 777) for directories.

However, we don't see these permissions when we create a file or directory. Actually, this default is transformed by subtracting the user mask from it to remove one or more permissions. To understand what this means, let's evaluate the current value of the mask by using umask without arguments:

$ umask

022

This is an octal number which has to be subtracted from the system default to obtain the actual default. This becomes 644 (666 - 022) for ordinary files and 755 (777 - 022) for directories. When we create a file on this system, it will have the permissions rw-r-r-. umask is a shell built-in command though it also exists as an external command. A user can also use this command to set a new default. Here's an extreme setting:

$ umask 000     All read-write permissions on

An umask value of 000 means that we haven't subtracted anything and this could be dangerous. The system's default then applies (666 for files and 777 for directories). All files and directories are then writable by all; nothing could be worse than that! However, a mask value of 666 or 777 doesn't make much sense either; we'll then be creating files and directories with no permissions.

$ps

PID   TTY   TIME            CMD

291 console   0:00  bash             The login shell of this user

Full Listing (-f): To get a detailed listing which also shows the parent of every process, use the -f (full) option:

$ ps -f

UID  PID  PPID  C  STIME  TTY        TIME  CMD

raj  367  291  0  12:35:16  console     0:00  vi create_user.sh

raj  291  1  0  10:24:58  console     0:00  -bash

raj 368  367  0  12:35:18  console     0:00  /usr/bin/bash -i

$ ps-u raj

PID   TTY    TIME    CMD

 378    ?   0:05   Xsun

403    ?   0:00   Xsession

339    pts/3  0:00   bash

346    pts/3  0:00   vi

347    pts/3  0:00   bash

478    ?   0:00   dtfile

Example:

To run a job with a low priority, the command name should be prefixed with

nice:

$ nice wc – uxmanual

or better still with

$ nice wc -1 uxmanual &

nice is a built-in command in the C shell, nice values are system-dependent and typically range from 1 to 19. Commands execute with a nice value that is generally in the middle of the range usually 10. A higher nice value implies a lower priority, nice reduces the priority of an process, thereby raising its nice value. We can also specify the nice value explicitly with the -n option:

$ nice -n 5 wc –l uxmanual &  Nice value increased by 5 units

A non-privileged user can't increase the priority of a process; that power is reserved for the super user. The nice value is displayed with the $ ps -o nice command.

$ rmdir pis   Directory must be empty

The rmdir can also delete more than one directory in one shot for instance, the three directories and subdirectories can be removed by using rmdir with a reversed set of arguments:

$ rmdir pis/data pis/progs pis

When we delete a directory and its subdirectories, a reverse logic has to be applied.

$ rmdir pis pis/progs pis/data

rmdir: directory "pis": Directory not empty

We observed one thing from the error message? rmdir, has silently deleted the lowest level subdirectories progs and data.

This error message leads to two important rules that we should remember when deleting directories:

(a) We can't delete a directory with rmdir unless it is empty. In this case, the pis directory couldn't be removed because of the existence of the subdirectories, progs and data, under it.

(b) We can't remove a subdirectory unless we are placed in a directory which is hierarchically above the one we have chosen to remove.

The first rule follows logically from the example above. To illustrate the second cardinal rule, try removing the progs directory by executing the command from the same directory itself:

$ cd progs

pwd

/home/kumar/pis/progs

$ rmdir /home/kumar/pis/progs Trying to remove the current directory rmdir: directory M/home/kumar/pis/progs": Directory does not exist

To remove this directory, we must position ourself in the directory above progs, ie, pis, and then remove it from there:

$ cd /home/kumar/pis

$ pwd

/home/kumar/pis

$ rmdir progs

Syntax:

chmod [options] permissions filename

There are three different permissions. They are:

Read (4): Permitted to read the contents of the file. In case of directory, you can view all the files and sub-directories in that directory

Write (2): Permitted to write to the file. In case of directory, you can create files and sub-directories

Execute (1): Execute the file as a program/shell script. In case of directory, You can enter into that directory.

Here in the above, the numbers in the brackets represents the numeric values for the corresponding permissions. If you want to have a combination of permissions add the required numbers. For example, for read and execute, it is 4+1= 5.

chmod [options]

-R: recursively change the permissions of a directory.

-v: Verbose

Chmod Examples in Linux / Unix:

1. Give read, write and execute permissions to everyone. Read, write and execute: 4+2+1=7

$ chmod 777 sample.sh

In the above example, you can see that the permissions are specified with a three digit number. The first digit is for user permissions, second is for group and third is for others permission. This type of representation is called octal representation. Alternatively, you can use the symbolic representation to give the permissions.

chmod ugo+rwx sample.sh

We will see more details about the symbolic representation later.

2. Give read permission to user, write permission to group and execute permission to others

$ chmod 421 sample.sh

3. Recursive permissions to directory

To give read and write permissions to all the users to a directory (including files and subdirectories) use the recursive option -R.

chmod -R 666 /dir

Symbolic Representation of Permissions: The following symbols are used to represent the users, groups and others:

• u: User
• g: Group
• o: Others
• a: All (user, group and others)

The following symbols represent the permissions:

• r: read
• W: write
• X: execute

The following symbols represent the permissions grant or revoke:

• + : Additional permissions. Selected permissions are added.
• -  : Revoke the permissions. Selected permissions are revoked.
• = : Specific permissions. Only selected permissions are assigned.

Examples

1. Remove write permission from group

$ chmod g-w sample.sh

This will only removes the write permission for the group.

2. Add new permission execute to others

$ chmod o+x sample.sh

In addition to the existing permissions, this will add execute permission to others.

3. Give only read permissions to the user

$chmod u=w sample.sh

This will remove the existing permissions to the user and gives only write permission to the user.

Syntax:

man <options> <command name>

Description: man is the system's manual viewer, it can be used to display manual pages, scroll up and down, search for occurrences of specific text and other useful functions.

Each argument given to man is normally the name of a program, utility or function. The manual page associated with each of these arguments is then found and displayed. A section number, if provided, will direct man to look only in that section of the manual. The default action is to search in all of the available sections, following a pre-defined order and to show only the first page found, even if page exists in several sections, General Options

-h,--help    Print a help message and exit.

-V,--version     Display version information and exit

-C file,--config-file=file   Use configuration file rather the defaut

of ~/.man path.

-d, --debug     Print debugging information

-D,--default   This option when used, is normally specified as the first soption; it resets man's behavior to its default. Its use is to reset those options that may have been set in $MANOPT. Any options that follow -I will have their usual effect.

--warnings[=wamings]  Enable warnings from the groff text formatter. Warnings are a comma-separated list of warning names, if it is not supplied, the default is "mac". See the "Warnings" node

                                     the groff info page for a list of available warning names.

Syntax:

telnet [option] [host [port]]

-4

Force IPv4 address resolution

-6

Force IPv6 address resolution

-8

Request 8-bit operation. This causes an attempt to negotiate the TELNET BINARYoption for both input and output. By default telnet is not "8-bit clean" (it does not recognize 8-bit character encodings such as Unicode).

-E

Disables the escape character functionality; that is, sets the escape character to "no character".

-L

Specifies an 8-bit data path on output. This causes the TELNET BINARY option to be negotiated on just output

-a

Attempt automatic login. Currently, this sends the user name via the USER variable of the ENVIRON option if supported by the remote system. The username is retrieved via the getlogin system call

-b address

Use bind on the local socket to bind it to a specific local address.

-d

Sets the initial value of the debug toggle to TRUE.

-r

Emulate rlogin. In this mode, the default escape character is a tilde. Also, the interpretation of the escape character is changed: an escape character followed by a dot causes telnet to disconnect from the remote host. A^Z (Control-Z) instead of a dot suspends telnet, and a ^] (Control-Close Bracket, the default telnet escape character) generates a normal telnet prompt. These codes are accepted only at the beginning of a line.

-S tos

Sets the IP type-of-service (TOS) option for the telnet connection to the value tos.

-eescapechar

Sets the escape character to escapechar. If no character is supplied, no escape character will be used. Entering the escape character while connected causes telnet to drop to command mode.

-I user

Specify user as the user to log in as on the remote system. This is accomplished by sending the specified name as the USER environment variable, so it requires that the remote system support the TELNET ENVIRON option. This option implies the -a option, and may also be used with the open command.

-n tracefile

Opens tracefile for recording trace information. See the set tracefile command below.

Host

Specifies a host to contact over the network.

Port

Specifies a port number or service name to contact. If not specified, the telnet port (23) is used.

Output: Sunos

Using suitable options, it can display certain key features of the operating system and also the name of the machine. The output will depend on the system.

(a) The current release and implementation name (-r and -s): Since UNIX comes in many flavors, vendors have customized a number of commands to behave in the way they want and not as AT&T decreed. A UNIX command often varies across versions so much so that we'll need to use the -r option to find out the version of operating system.

$ uname –r

5.8       This is SunOS 5.8

The implementation name of this operating system can be obtained with the

s option:

$ uname –s

SunOS

Note: The complete name of the operating system is actually a combination of the output of the two options

(b) The Machine Name (-n): If machine is connected to a network, then it must have a name (called hostname). If network is connected to the Internet, then this hostname is a component of machine's domain name. The -n option display the hostname:

$ uname -n

mercury    The first word of the domain name

The same output would be obtained with the hostname command. To copy files from a remote machine named mercury, we have to run ftp mercury.

$ passwd

passwd: Changing password for Chintamani

Enter login password: ****

New password: ****

Re-enter new password: ****

passwd: password successfully changed for Chintamani

Syntax:

stty [option][-][mode]

option:

-a (all): The -a option displays the current settings,

$ stty –a

speed 38400 baud; rows =25; columns=80; ypixels =0; xpixels=0;

intr = ^c; quit =\; erase = ^; kill=^u;

eof=^d;eol=<undef>; eol2^c; quit =\; erase = ; kill=^u;

eof=^d;eol=<undef>; eol2 = <undef>; swtch = <undef>;

start=^; stop=^s; susp=^z; dsusp=^y: -parenb -parodd cs8

-cstopb -hupclcread - clocal -loblk -crtscts -crtsxoff-pare xt

-ignbrk brkint ignpar -parmrk -inpck -istrip -inclr -igncr icrnl -iuclcixon

-ixany -ixoff imaxbelisig icanon -xcase echo echoe echok-echonl - noflsh

-tostop echocti -echoprt echoke -defecho -flusho -pendin iextenopost

-olcuc onclr-ocrnl -onocr-onlret -ofill -ofdel tab3

Changing the settings: Whether backspacing should Erase Character(echo): The keyword echo decides whether backspacing over a character sometimes removes it from sight and sometimes doesn't. Since it is set here backspacing removes the character from display. The same keyword can be used to reverse string.

stty-echoe

Entering a password through a shell script (echo): The echo setting has to be manipulated to let shell programs accept a password-like string that must not be displayed on the screen. By default, the option is turned on, but we can turn it off in the following way:

stty –echo    Turns off keyboard input

Changing the end of file key(eof) When using bc, ctrl + d was used to terminate the input. Instead of ctrl +d ctrl + a can be used as the end of character.

stty eof \^a

When everything fails(sane) stty also provides another argument to set the terminal characteristics to values that will work on most terminals.

stty sane    Restores sanity to the terminal

Syntax:

cal [options] [[[day] month) year]

Options:

-1, --one    Display single month output (This is the default).

-3, --three    Display three months spanning the date.

-n. --months numbe Display number of months, starting from the month

containing the date

-S, --span  Display months spanning the date

-s, -sunday   Display Sunday as the first day of the week.

Syntax:

bc [options]

Options:

-c   Compile only. The output is de commands that are sent to the standard output

-1    Define the math functions and initialize scale to 20, instead of the default zero.Filename Name of the file that contains the basic calculator commands to be calculated this is not a necessary command.

Example:

1. bc

Output

bc 1.06 Copyright 1991-1994,1997,1998,2000 Free Software Foundation, Inc. This is free software with ABSOLUTELY NO WARRANTY. For details type 'Warranty'. 9*2 18

The above command used is for mathematical calculations.

2. bc -1

Output:

bc 1.06 Copyright 1991-1994, 1997,1998,2000 Free Software Foundation, Inc. This is free software with ABSOLUTELY NO WARRANTY. For details type

warranty', 1+2 3

The above command displays the sum of ‘1+2’

3. bc calc.bxt

Output:

bc 1.06 Copyright 1991-1994 1997 1998, 2000 Free Software Foundation, Inc. This is free software with ABSOLUTELY NO WARRANTY. For details type 'warranty'.

Syntax :

script [ -a ][ filename ]

Options:

-a  Append the session record to filename, rather than overwrite it.

Note:

script places everything that appears on the screen in filename, including

prompts.

Syntax:

date [OPTION]... [+FORMAT]

date [-u |-utc|--universal] [MMDDhhmm[[CC][YY][ss]]

Options:

       -d. --date=STRING display time described by string STRING, as opposed    to the default, which is 'now'

-f, --file-DATEFILE like --date, but processed once for each line of file        DATEFILE.

-s, --set-STRING set time described by string STRING.

-u, -utc, --universal print or set Coordinated Universal Time.

-help Display a help message and exit.

--version Display version information and exit.

Date Format

Format is a sequence of characters which specifies how output will appear. It comprises some combination of the following sequences:

%%   a literal percent sign ("%").

%a   The abbreviated weekday name (e.g., Sun).

%A   The full weekday name (e.g., Sunday).

%b  The abbreviated month name (e-g. Jan).

%B   locale's full month name (e.g., January).

%c   The date and time (e.g., Thu Mar 3 23:05:25 2005).

%C   The current century; like %Y, except omit last two digits (e.g, 20)

date examples

date

Running date with no options will output the system date and time, as in the

following output: Thu Feb 8 16:47:32 MST 2001

date -s "11/20/2003 12:48:00”

Set the system date and time to November 20, 2003, 12:48 PM.

date "+DATE: %m/%d/%y%n TIME: %H:%M:%S"

Outputs the date and time in the following format:

DATE: 02/08/21

TIME: 16:44:55

Syntax :

wc [OPTIONS]…[FILE].

Option:

-c, --bytes  : print the byte counts

-m, -chars : print the character counts

-1 –lines : print the newline counts

Snytax:

             $ wc –c file1

456 file1

$ gzip file1

$ wc-c file1.gz

156 file1

$ gzip file1 file2

Option:

-1: If we want to know how much compression we have achieved for both files,

we use -l option.

$ gzip –1 file1 file2

Compressed  uncompressed           ratio   uncompressed name

156   456   79.6%  file1

456   756   65.5%  file2

612   1212   78.4%

(totals)

-d: To uncompress/decompress a file, use -d option or gunzip command.

 $ gzip -d file1.gz

Or

$ gunzip file1.gz

-r: Like cp, we can also compress and decompress a directory structure with

option

$ gzip -r doc

//it will compress the entire file in the doc directory. Similarly we can decompress all the files in the doc directory with following command,

$ gunzip –r doc

Syntax:

Lp -I request-ID (option) file nam

Example:

To print a file named rfc882.ps lp command is used in the following way:

$ lp rfc882.ps

request Id Is prl_320 (1 file)

$_

                  The lp command returns the prompt immediately after the output.

                   lp options:

-d: lp accepts the command as a default printer has been defined. If more than one printer is attached then we can use -d option with the printers name.

lp-dlaser chap01.ps

-t: The -t(title) option followed by the title string prints the title on the first page.

lp--t*First chapter* chap01.ps

-m: The -m(mail) option is used to notify the user that the file has been printed. Multiple copies of the same file can be printed by using the -n option.

lp-n3-m chap01.ps

$ od -b file

0000000   127  150  151  164  145  040  163  160  141  143

145…………..

$ od -bc file

0000000   127  150  151  164  145  040  163  160  141  143

145…………..

  W h I t e s p a c

e………………

1. –c   create an archive
2. –x   extract files from archive
3. –t   display files in archive
4. –f   arch name the archive arch

Only one option at a time can be used. To compress and decompress gzip and gunzip are used respectively.

1. Creating an Archive: To create an archive, the name of the archive has to be specified with -f option, the copy or write operations as -c and filenames as arguments. Additionally -v option is used to display the progress while the tar command works.

$ tar -cvf archive.tar libc.html User_Guide.ps

a libc.html 3785K

a User_Guide.ps 364K

Using gzip with tar: If the created file is very big, the compression of the file is done in the following way using the gzip command:

gzip archive.tar   Archived and compressed.

The above command creates a "tar-gzipped" file,archive.tar.gz. This file can then be sent out by ftp or as an email attachment.

2. Extracting file from the archive (-x): tar uses -x option to extract files from an archive.

tar -xvf progs.tar   Extracts three directories

To extract any file using tar command the file has to be to be unzipped first using gunzip command and then it is extracted.

$ gunzip archive.tar.gz    Retrieves archive.tar

$ tar -xvf archive.tar     Extract files

x libc.htm, 3875302 bytes, 7569 tape blocks

x User_Guide.ps,372267 bytes, 728 tape blocks

To extract a single file from the archive following command can be used:

tar -xvf archive.tar User guide.ps

3. Viewing the archive (-t): To view the archive -t(table of contents) option is used. It doesn't extract the files; it normally shows the attributes of the files.

Star-tvf archive.tar

-rw-r-r-102/10 3875302 Aug 24 19:49 2002 libc.html

-rw-r---102/10 372267 Aug 24 19:48 2002 User_Guide.ps

The operating system is supported by multiple file systems. The df (disk free) command reports the amount of free space available for each file system separately:

#df

/   (/dev/dsk/c0t0d0s0):3491876  blocks  483932 files

/usr   (/dev/dsk/cotod0s4):2434820  blocks  458466 files

/proc   (/proc ):    0 blocks 15875    files

/dev/fd  (fd):      0 blocks 0    files

/etc/mnttab  (mnttab):     0 blocks 0    files

The above output is inferred as, from the first line we can say that the root file system (/) has 3491876 blocks of disk space free. It also has 483932 inodes free.

The-t (total) option include the above output as well as the total free space in the file system. -k option is the informative option which reports the free space in units of KB.

$ df -k// usr

du is the command which reports the usage of disk by recursive examination of the directory tree.

Example:

#du/home/sales/tml

11554    /home/sales/tml/forms

12820   /home/sales/tml/data

……….

25170    /home/sales/tml

By default, du lists the usage of each subdirectory of its argument and finally produces a summary.

To enlist the summary of the usage -s option can be used.

#du-s /home/sales/tml

25170 /home/sales/tml

Most of the dynamic space is used by the users' home directories and data files. du with -s command can be used to report each user's home directory.

#du-s /home/*

144208 /home/henry

98920 /home/image

du with -a command can also report each file in a directory

mount-t ext2 /dev/hda3/oracle     linux

Snytax:

  nl [option] filename

Options:

-b, --body-numbering=STYLE   use STYLE for numbering body lines

-i, --line-increment=NUMBER  line number increment at each line

-1, -join-blank-lines=NUMBER  group of NUMBER empty lines counted as one

-n, -number-format=FORMAT  insert line numbers according to FORMAT

-v, --starting-line-number=NUMBER first line number on each logical page

-w. --number-width=NUMBER use NUMBER columns for line numbers

STYLE is one of:

A   number all lines

T  number only nonempty lines

N  number no lines

FORMAT is one of:

1n  left justified, no leading zeros

Rm  right justified, no leading zeros

Rz  right justified, leading zeros

Example:

$ cat fruit.txt

mango

apple

banana

litchie

orange

$ nl frult.txt

1 mango

2 apple

3 banana

4 litchie

5 orange

$ nl i5 fruit.txt

1 mango

6 apple

11 banana

16 litchie

21 orange

The following example numbers only the lines that begin with a capital letter A (matching on the regular expression /^A/), filename is optional.

$nl -b p^A filename

apple

1 Apple

 BANANA

2 Allspice

strawberry

Description: Display all or parts of a file, type q to quit, press space bar to continue

Syntax:

$ page [option](file list)

$pg [option] file list

Options:

-c Clears the screen before displaying the next page of the file. This can be quicker than watching pages scroll by.

-d  Displays a prompt at the bottom of the screen-involving brief instructions.

-f  Wrap text to fit the screen width and judges the page length accordingly.

-1  Ignore form feeds at the end of a page.

-s Squeeze ignores multiple blank lines.

The following commands may be entered at the prompt. Commands preceded by i accept a number as argument, positive or negative. If this argument starts with + or -, it is interpreted relative to the current position in the input file, otherwise relative to the beginning.

I<newline>   Display the next or the indicated page.

id, ^D  Display the next halfpage. If i is given, it is always interpreted relative to the current position

/1   Display the next or the indicated line.

/f Skip a page forward. i must be a positive number and is always interpreted relative to the current position

iw, iz Behave as <newline> except that i becomes the new page size.

.,^L   Redraw the screen.

 $   Advance to the last line of the input file.

/n   Advance to the next file or i files forward.

/p   Reread the previous file or i files backward.

q,Q   Quit

Syntax :

Join [options] file1 file2

options:

-1 field number: Join on the specified field number in the first file.

-2 field number: Join on the specified field number in the second file.

-j field number Equivalent to -1 fieldnumber and -2 fieldnumber.

-o list : displays only the specified fields from both the files.

-t char: input and output field delimiter.

-a filenumber: Prints non matched lines in a file.

-i: ignore case while joining.

Examples of the unix join command :

$ cat 1.txt

1 abc

2 Imn

3 pqr

$ cat 2.txt

1 abc

3 Imn

9 opq

$ join 1.txt 2.txt

1 abc abc

3 pgr Imn

Since the two files are trying to match on the 1st column, and both have a 1 and a 3 in that column. To tell join to use the second column to join with, we type:

$join -1 2 -2 2 1.txt 2.txt

* (where "-1 2" stands for the 2nd field of the 1st file, and "-2 2" stands for the 2nd field of the 2nd file.

abc 1 1

Imn 2 3

which are just those fields that match in both files. This is referred to as an inner join. Inner joins look for rows that match rows in the other table. The problem with inner joins is that only rows that match between tables are returned.

$ join -a1 -1 2 -2 2 1.txt 2.txt

#(where "-al" says include all the records from the first file).

abc 1 1

Imn 2 3

pqr 3

this is missing a number for pqr for the second file (since there is no pqr in that file) and is missing "9 opq" from the second file. This is an example of a left outer join, called such because it includes all of the rows from the left (or first) file specified.

$ join -a1 -a2  -1 2 -2 2 1.txt 2.txt

#(adding "-a2" to tell join to also include all records from the second file).

abc 1 1

Imn 2 3

opq 9

pqr 3

Which has all of the records. This is an example of a full outer join since it has all of the rows from both files. (Missing from these examples is the case where we had the -a2 without the -al. That would have produced a right outer join which contained all of the records from the second (right) file and only those rows from the first (left) file that matched).

While this example has all of the rows from both files, we still have a problem since we cannot tell which file the count is for on the last two records.

ftp command is used to ftp protocol using which files are transferred over two systems.

Syntax :

ftp [option] hostname

Option :

(i) -d - enable debugging.

(ii) -g - disable filename globbing.

(iii) -i - turn off interactive prompts.

(iv) -v - verbose on show all responses from remote server.

ftp hostname by default will connect to the system, it 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.

Syntax:

rlogin [option] host

Option:

(i) -8   - will allow 8 bit data to pass, instead of 7-bit data.

(ii) -e c -will use escape character c.

(iii) -l user  - will login as user to remote host, instead of same as local host.

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:

talk userid@hostname

Finding Out who's logged in, in detail

$ finger

Login   Name    TTY   Idle  when   where 

Albert  Albert sahu   pts/19   Fri 09:40    (172.16.0.19)

Robert  Robert dewangan  pts/29  12  Fri 14:40    (172.16.0.16)

Sam  Sam verma  pts/39  16  Fri 16:40    (172.16.0.20)

The first column shows the user's name. There are 3 users currently working on the system. The second column shows the full name of the user. The third field shows their terminals preceded by an asterisk if the terminal doesn't have write permission. Fourth column shows the idle time - the time that has elapsed since the last keystroke was entered. The last column shows the machine id from where the user logged in

Like who command, finger command can also provide details about single user.

$ finger Albert

Login Name: Albert

Directory: /home /users/ Albert   shell: /usr/bin/bash

On since Jan 13 12:56:33 on pts/4 from 172.16.0.15

No mail

No plan

Syntax:

cpio flags [options]

flags: -i, -o, -p

cpio -i [options] [patterns]

cpio -i copy in files whose name matches 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 names are given on standard output

cpio –p      : Copy files to another directory on the same system.

Options :

(i) t - Lists files in archive (must use with -i).

(ii) c - Read or write header information as ASCII character.

(iii) d - Create directories as needed.

(iv) 1 - Link files instead of copying.

(v) o file - Direct output to a file.

(vi) r - Rename files interactively.

(vii) RID - Reassign file ownership and group information to the user's login   ID.

(viii) - Print a list of filenames.

(ix) fexp -  Copies all files except those in exp.

Examples

$ ls | cpio-ov > /dev/rdsk/abc

Array.pl

Calendar

Script44.sh

246 blocks

$ cpio -iv < /dev/rdsk/abc

Array.pl

Calendar

Script44.sh

256 blocks

$ cpio -- "*.c"< /dev/rdsk/abc

$ cpio ivf "*.c"< /dev/rdsk/abc

#it will select all files except those in the expression i.e. file with .c extension.