Basics of VI Editor of Linux

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                       Opening a file     

vi filename: Creating text

Edit modes: These keys enter editing modes and type in the text

of your document.

i     Insert before current cursor position

I     Insert at beginning of current line

a     Insert (append) after current cursor position

A     Append to end of line

r     Replace 1 character

R     Replace mode

<ESC> Terminate insertion or overwrite mode

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                 Deletion of text

x        Delete single character

dd      Delete current line and put in buffer

ndd    Delete n lines (n is a number) and put them in buffer

J        Attaches the next line to the end of the current line (deletes carriage return).

u        Undo last command

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                 CUT AND PASTE

yy      Yank current line into buffer

nyy    Yank n lines into buffer

p        Put the contents of the buffer after the current line

P       Put the contents of the buffer before the current line

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                CURSOR POSITIONING

^d              Page down

^u              Page up

:n               Position cursor at line n

:$               Position cursor at end of file

^g               Display current line number

h,j,k,l          Left,Down,Up, and Right respectively. 

                  Your arrow keys should also work if your keyboard mappings are anywhere near same.

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                STRING SUBSTITUTION

:%s#string1#string2#[g]       Substitute string2 for string1 on lines n1 to n2. If g is included (meaning global), 
                                           all instances of string1 on each line are substituted. If g is not included,only
                                           the first instance per matching line is substituted.

    

    ^ - matches start of line

    . - matches any single character

    $ - matches end of line

These and other "special characters" (like the forward slash) can be "escaped" with \

i.e to match the string "/usr/STRIM100/SOFT" say "\/usr\/STRIM100\/SOFT"

Examples:

:1,$:s/dog/cat/g                   Substitute 'cat' for 'dog', every instance

                                   for the entire file -lines 1 to $ (end of file)

:23,25:/frog/bird/                 Substitute 'bird' for 'frog' on lines

                                   23 through 25. Only the first instance

                                   on each line is substituted.

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              SAVING, QUITTING and other "ex" Commands

These commands are all prefixed by pressing colon (:) and then entered in the lower left corner of the window. They are called "ex" commands because they are commands of the ex text editor - the precursor line editor to the screen editor

vi. You cannot enter an "ex" command when you are in an edit mode (typing text onto the screen)

Press <ESC> to exit from an editing mode.

:w                         Write the current file.

:w new.file             Write the file to the name 'new.file'.

:w!                        Existing.file Overwrite an existing file with the file currently being edited.

:wq                       Write the file and quit.

:q                          Quit.

:q!                         Quit with no changes.

:e filename             Open the file 'filename' for editing.

:set number            Turns on line numbering

:set nonumber        Turns off line numbering

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Staring Guide to Unix- Some basic Commands

We will cover the following sections in this article:

1. Directories
2. Moving around the file system
3. Listing directory contents
4. Changing file permissions and attributes
5. Moving, renaming, and copying files
6. Viewing and editing files
7. Shells
8. Environment variables
9. Interactive History
10. Filename Completion
11. Bash is the way cool shell
12. Redirection
13. Pipes
14. Command Substitution
15. Searching for strings in files: The grep  command
16. Searching for files : The find command
17. Reading and writing tapes, backups, and archives: The tar command 
18. File compression: compress, gzip, and bzip2
19. Looking for help: The man and apropos commands

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   Basic UNIX Command Line (shell) navigation  

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Directories: 

File and directory paths in UNIX use the forward slash "/"

to separate directory names in a path.

examples:

/              "root" directory

/usr           directory usr (sub-directory of / "root" directory)

/usr/STRIM100  STRIM100 is a subdirectory of /usr

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 Moving around the file system:

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pwd               Show the "present working directory", or current directory.

cd                Change current directory to your HOME directory.

cd /usr/STRIM100  Change current directory to /usr/STRIM100.

cd INIT           Change current directory to INIT which is a sub-directory of the
  current  directory.

cd ..             Change current directory to the parent directory of the current directory.

cd $STRMWORK      Change current directory to the directory defined by the   

Environment variable 'STRMWORK'.

cd ~bob           Change the current directory to the user bob's home directory (if you have permission).

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 Listing directory contents:

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ls    list a directory

ls -l    list a directory in long ( detailed ) format

   for example:

$ ls -l

drwxr-xr-x    4 cliff    user        1024 Jun 18 09:40 WAITRON_EARNINGS

-rw-r--r--    1 cliff    user      767392 Jun  6 14:28 scanlib.tar.gz

^ ^  ^  ^     ^   ^       ^           ^      ^    ^      ^

| |  |  |     |   |       |           |      |    |      | 

| |  |  |     | owner   group       size   date  time    name

| |  |  |     number of links to file or directory contents

| |  |  permissions for world

| |  permissions for members of group

| permissions for owner of file: r = read, w = write, x = execute -=no permission

type of file: - = normal file, d=directory, l = symbolic link, and others...

ls -a        List the current directory including hidden files. Hidden files

starts with "."

ls -ld *     List all the file and directory names in the current directory

using long format. Without the "d" option, ls would list the                contents of any sub-directory of the current. With the "d" option, ls just lists them like regular files.

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Changing file permissions and attributes

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chmod 755 file       Changes the permissions of file to be rwx for the

owner,and rx for the group and the world. (7 = rwx = 111  binary. 5 = r-x = 101 binary) chgrp user file      

 Makes file belong to the group user.

chown cliff file     Makes cliff the owner of file.

chown -R cliff dir    Makes cliff the owner of dir and everything in its directory

tree.

You must be the owner of the file/directory or be root before you can do any of

these things.

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 Moving, renaming, and copying files:

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cp file1 file2          copy a file

mv file1 newname        move or rename a file

mv file1 ~/AAA/         move file1 into sub-directory AAA in your home directory.

rm file1 [file2 ...]    remove or delete a file

rm -r dir1 [dir2...]    recursivly remove a directory and its contents BE CAREFUL!

mkdir dir1 [dir2...]    create directories

mkdir -p dirpath        create the directory dirpath, including all implied

directories in the path.

rmdir dir1 [dir2...]    remove an empty directory

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Viewing and editing files:

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cat filename      Dump a file to the screen in ascii.

more filename     Progressively dump a file to the screen: ENTER = one line down

                  SPACEBAR = page down  q=quit

less filename     Like more, but you can use Page-Up too. Not on all systems.

vi filename       Edit a file using the vi editor. All UNIX systems will have vi

  in some form.

emacs filename    Edit a file using the emacs editor. Not all systems will have

  emacs.

head filename     Show the first few lines of a file.

head -n  filename Show the first n lines of a file.

tail filename     Show the last few lines of a file.

tail -n filename  Show the last n lines of a file.

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 Shells

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The behavior of the command line interface will differ slightly depending

on the shell program that is being used.

Depending on the shell used, some extra behaviors can be quite nifty.

You can find out what shell you are using by the command:

    echo $SHELL

Of course you can create a file with a list of shell commands and execute it like

a program to perform a task. This is called a shell script. This is in fact the

primary purpose of most shells, not the interactive command line behavior.

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Environment variables

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You can teach your shell to remember things for later using environment variables.

For example under the bash shell:

export CASROOT=/usr/local/CAS3.0               Defines the variable CASROOT with
the value /usr/local/CAS3.0.

export LD_LIBRARY_PATH=$CASROOT/Linux/lib      Defines the variable

                                                LD_LIBRARY_PATH with

                                             the value of CASROOT with /Linux/lib
      appended,     
                                            or /usr/local/CAS3.0/Linux/lib

By prefixing $ to the variable name, you can evaluate it in any command:

cd $CASROOT         Changes your present working directory to the value of CASROOT

echo $CASROOT       Prints out the value of CASROOT, or /usr/local/CAS3.0

printenv CASROOT    Does the same thing in bash and some other shells.

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Interactive History

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A feature of bash and tcsh (and sometimes others) you can use

the up-arrow keys to access your previous commands, edit

them, and re-execute them.

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Filename Completion

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A feature of bash and tcsh (and possibly others) you can use the

TAB key to complete a partially typed filename. For example if you

have a file called constantine-monks-and-willy-wonka.txt in your

directory and want to edit it you can type 'vi const', hit the TAB key,

and the shell will fill in the rest of the name for you (provided the

completion is unique).

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Bash is the way cool shell.

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Bash will even complete the name of commands and environment variables.

And if there are multiple completions, if you hit TAB twice bash will show

you all the completions. Bash is the default user shell for most Linux systems.

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Redirection:

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grep string filename > newfile           Redirects the output of the above grep

                                         command to a file 'newfile'.

grep string filename >> existfile        Appends the output of the grep command

                                         to the end of 'existfile'.

The redirection directives, > and >> can be used on the output of most commands

to direct their output to a file.

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Pipes:

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The pipe symbol "|" is used to direct the output of one command to the input

of another.

For example:

ls -l | more   This commands takes the output of the long format directory list command

               "ls -l" and pipes it through the more command (also known as a filter).

               In this case a very long list of files can be viewed a page at a time.

du -sc * | sort -n | tail 

               The command "du -sc" lists the sizes of all files and directories in the current working directory. That is piped through "sort -n" which orders the output from smallest to largest size. Finally, that output is piped through "tail" which displays only the last few (which just happen to be the largest) results.

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Command Substitution

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You can use the output of one command as an input to another command in another way

called command substitution. Command substitution is invoked when by enclosing the

substituted command in backwards single quotes. For example:

cat `find . -name aaa.txt`

which will cat ( dump to the screen ) all the files named aaa.txt that exist in the current directory or in any subdirectory tree.

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Searching for strings in files: The grep  command

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grep <string> <filename>   prints all the lines in a file that contain the string

or
cat <filename> |grep <string>

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Searching for files : The find command

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find search_path -name filename

find . -name aaa.txt    Finds all the files named aaa.txt in the current directory or any subdirectory tree.

find / -name vimrc      Find all the files named 'vimrc' anywhere on the system.

find /usr/local/games -name "*xpilot*"      

                        Find all files whose names contain the string 'xpilot' which exist within the '/usr/local/games' directory tree.

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Reading and writing tapes, backups, and archives: The tar command 

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The tar command stands for "tape archive". It is the "standard" way to read

and write archives (collections of files and whole directory trees).

Often you will find archives of stuff with names like stuff.tar, or stuff.tar.gz.  This is stuff in a tar archive, and stuff in a tar archive which has been compressed using the gzip compression program respectivly.

Chances are that if someone gives you a tape written on a UNIX system, it will be in tar format, and you will use tar (and your tape drive) to read it.

Likewise, if you want to write a tape to give to someone else, you should probably use

tar as well.

Tar examples:

tar xv      Extracts (x) files from the default tape drive while listing (v = verbose) the file names to the screen.

tar tv      Lists the files from the default tape device without extracting them.

tar cv file1 file2     

            Write files 'file1' and 'file2' to the default tape device.

tar cvf archive.tar file1 [file2...]  

            Create a tar archive as a file "archive.tar" containing file1,

            file2...etc.

tar xvf archive.tar  extract from the archive file

tar cvfz archive.tar.gz dname   

       Create a gzip compressed tar archive containing everything in                   the directory 'dname'. This does not work with all versions of tar.

tar xvfz archive.tar.gz         

            Extract a gzip compressed tar archive.  Does not work with all
                    versions of tar.

tar cvfI archive.tar.bz2 dname  

            Create a bz2 compressed tar archive. Does not work with all versions
    of tar

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File compression: compress, gzip, and bzip2

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The standard UNIX compression commands are compress and uncompress. Compressed files have

a suffix .Z added to their name. For example:

compress part.igs    Creates a compressed file part.igs.Z

uncompress part.igs  Uncompresseis part.igs from the compressed file part.igs.Z.

                     Note the .Z is not required.

Another common compression utility is gzip (and gunzip). These are the GNU compress and uncompress utilities.  gzip usually gives better compression than standard compress, but may not be installed on all systems.  The suffix for gzipped files is .gz

gzip part.igs     Creates a compressed file part.igs.gz

gunzip part.igs   Extracts the original file from part.igs.gz

The bzip2 utility has (in general) even better compression than gzip, but at the cost of longer times to compress and uncompress the files. It is not as common a utility as gzip, but is becoming more generally available.

bzip2 part.igs       Create a compressed Iges file part.igs.bz2

bunzip2 part.igs.bz2 Uncompress the compressed iges file.

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Looking for help: The man and apropos commands

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Most of the commands have a manual page which give sometimes useful, often more or less detailed, sometimes cryptic and unfathomable discriptions of their usage. Some say they are called man pages because they are only for real men.

Example:

man ls      Shows the manual page for the ls command

You can search through the man pages using apropos

Example:

apropos build     Shows a list of all the man pages whose discriptions contain the word "build"

Do a man apropos for detailed help on apropos.

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--Regards
   V3nom
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