1) logout = exit a login shell

A login shell, is your topmost shell, and is started when you log in.

When you terminate a login shell (via the commands `exit’, `logout,’ or the end of file [^D]), you are logged out completely.

A `sub-shell’ is a shell created after login, either by loading a new shell or opening a window with a graphics interface. A sub-shell usually will not accept the command `logout’ to terminate, you must use `exit’ or ^D.
When you terminate a sub-shell, you are returned to the process or shell that created it.

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2) finger = user information lookup program

usage : finger [-b] [-f] [-h] [-i] [-l] [-m] [-p] [-q] [-s] [-w] [username]

example : finger -q username

-b Suppress printing the user’s home directory and shell in a long format printout.
-f Suppress printing the header that is normally printed in a non-long format printout.
-h Suppress printing of the .project file in a long format printout.
-i Force “idle” output format, which is similar to short format except that only the login name, terminal, login time, and idle time are printed.
-l Force long output format.
-m Match arguments only on user name (not first or last name).
-p Suppress printing of the .plan file in a long format printout.
-q Force quick output format, which is similar to short format except that only the login name, terminal, and login time are printed.
-s Force short output format.
-w Suppress printing the full name in a short format printout.

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3) alias = create a ‘shortcut’ to a command.

The format is alias name=’command’. Example:

alias home=’cd /home/dave/public_html’

just by typing home will put you in /home/dave/public_html directory

To see the list of alias already set type alias

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4) ln = make links between files

ln command has two types

a) hard link = to assign a keyword to link to a file deep in directory, so easier to open it. Example: I am always working on this file /home/amrun/projects/bubblegum/secret.txt. To make it easier to access it everyday i create a hard link : ln /home/amrun/projects/bubblegum/secret.txt bbgumformula

Now i can just open bbgumformula it will directly open the file secret.txt

b) symbolic link = to create a link to a directory, must use symlink. Symlinks are also required when linking to a file on a different disk partition or on a network.

ln -s /dev/fd0 A:

ln -s /etc/httpd/conf web

The first example allows you to access the floppy drive as drive A, just like in DOS, and the second creates a directory entry called web that can be used instead of /etc/httpd/conf.

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5) touch = changes the date/time stamp of the file filename to the current time. Creates an empty file if the file does not exist.

EXAMPLE

% touch analysis_data.xls

it changes the timestamp of file analysis_data.xls to the current time.

There are three date/time values associated with every file on an ext2 filesystem:

– the time of last access to the file (atime)
– the time of last modification to the file (mtime)
– the time of last change to the file’s inode (ctime).

Touch will change the first two to the value specified, and the last one always to the current system time.

OPTIONS

-a, –time=atime, –time=access, –time=use
Change the access time only.

-c, –no-create
Do not create files that do not exist.

-d, –date time
Use time (which can be in various common formats)
instead of the current time. It can contain month
names, timezones, `am’ and `pm’, etc.

-m, –time=mtime, –time=modify
Change the modification time only.

-r, –file reference-file
Use the times of reference-file instead of the cur-
rent time.

-t MMDDhhmm[[CC]YY][.ss]
Use the argument (months, days, hours, minutes,
optional century and years, optional seconds)
instead of the current time.

For details, some good example: http://www.linfo.org/touch.html

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