History Command

1
History Command

• UNIX records all of the commands executed
• Up arrow displays the previous command
• Successive up arrows step through the previous
  commands
• The variable HISTFILE contains a record of all
  commands
• gthistory gt commands creates a file with a record
  of past executed commands

2
The script command

• The script command is handy
• gtscript OR gtscript scriptFile
• It logs all your input and system output to a
  file
• If you do not specify a file, the log goes to a
  file called typescript
• Type gtexit to terminate the logging

3
Escaping special characters

• Problem we might want to override special
  characters and have UNIX interpret them
  literally
• Example
• gtecho HOST echoes the host computer plus the
  home directory name
• gtecho \HOST \ echoes the literal string
• gtecho 'HOST ' echoes everything in quotes
  literally
• gtecho "HOST " echoes everything except for \
  and

4
The tar command

• Problem want to copy a bunch of files at once
• Solution tar glues a series of files together
• Note this is not compression
• tar commands
• Glue files together gttar cf tarfile fileList
• Verbose output tar -cvf tarFile fileList
• List files in a tarFile tar -tf tarFile
• Extract files from tarFile gttar -xvf tarFile
• Note The dash is not needed in the above commands

5
The compress utilities

• Compression greatly reduces the size of the files
  being transferred
• Compress a file and create a .gz extensiongtgzip
  fileName
• Uncompress a file to its original namegtgunzip
  fileName.gz or gtgzip d fileNameOr gt tar zxovf
  fileName.tar.gz
• Full procedure
• First tar, then gzip
• First, extract, then untar

6
Communicating with users

• gttalk username starts a chat program
• gtmail initiates a basic mail program
• gtfinger username displays the content of a file
  called /.plan
• Procedure
• Suppose we are user harley
• echo whatever gt /.plan
• Other users can type gtfinger harley
• whatever will display on their terminal

7
UNIX Toolbox Philosophy

• Create powerful command line tools
• Each does one thing
• Each does it very well
• Design these tools to work well together
• The tools handle streams
• Filters are commands whose inputs and outputs are
  stream
• Job is to transform the input
• input is either from stdin or a file
• The tools are normally C programs

8
Streams and Redirection

• Stream a flow of data from source to sink
• C programs have default stream sources or sinks
• stdin standard input (keyboard)
• stdout standard output (monitor)
• stderr error output (often same as stdout)
• Redirection alter the default source or sink
• Examples
• redirect stdout to a file gtls gt fileName
• redirect a file list and append to a filegtls
  gtgt filename
• redirect input from a file instead of stdinmail
  username ltmessage
• redirect error messages grep harley 2gt file
• redirect both stdout and stderr grep harley gt
• redirect, append both stdout and stderr grep
  harley gtgt

9
Concatenating files

• Method one (cp command)
• gtcp file1 file2 file3 destination
• Method two (cat command with redirection)
• cat jnk.txt grades gtboth.txt
• Note cat is the command to type the contents of
  a file
• Method three (concatenation redirection)
• cat jnk.txt gtboth.txt
• cat grades gtgtboth.txt

10
Pipes

• Send the output of one command to the input of
  the next (cmd1 cmd2)
• The pipe character
• Example ls grep a sort u
• Example ls al more

11
Editors History

• ed a line editor (Ken Thompson)
• ex An improved version of ed (Bill Joy)
• sed stream editor, can apply editing commands
  from the command line using streams
• vi Screen oriented text editor (We will use this
  one)
• Standard UNIX editor
• available on all UNIX systems
• smaller and faster than emacs
• minimal keystrokes to do tasks, hard to learn
• emacs (Richard Stallman)
• powerful, cumbersome, part of the GNU IDE
• Others these work more like those on windows,
  but they are not guaranteed to be on every UNIX
  system

12
vi editor

• Enter and exit the program
• To enter gtvi fileName
• To exit colon and then wq (write and quit) or q!
  (quit without write)
• Modes
• insert mode input text into a file
• command mode keyboard command key
• last line mode longer commands

input
command key
esc
command
or /
esc
last-line
13
File Pointer

• All commands are relative to a single file
  pointer
• Central to using vi is navigating around the file
• Navigation commands
• arrows work as you would expect on most vi
• Go to line 1 1G
• Go to line 50 50G
• Go forward one word w
• Go to the end of the line
• Go to the beginning of the line

14
Delete, Cut, Copy, Paste

• delete one word dw
• delete 4 words 4dw or d4w
• delete (cut) 50 lines 50dd
• yank (copy the current line y
• yank (copy) 50 lines 50y
• yank (copy) into one of 26 buffers buffer c "cy
• paste cut/copied text after the current line P
• paste cut/copied text before the current line p
• paste from buffer c "cp
• delete one character x
• delete 50 characters 50x

15
More vi Commands

• Undo command after a mistake u
• Undo all recent commands U
• join this line and the next j
• joint four lines 4j
• replace a single character r
• Save and exit ZZ
• Change the tab stops set tabstop4
• Entering unix commands sh

16
vi Insert Mode Examples

• change rest of a line until ltescgt c
• Change a word until ltescgt cw
• Change line until ltescgt cc
• Insert before file pointer until you ltescgt i
• Append after file pointer until ltescgt a
• Insert below until ltescgt o
• Insert above until ltescgt O
• Replace until ltescgt R

17
VI Last-Line examples

• Search for the word cat /cat
• Search backwords for cat ?cat
• Replace all this line cat by dog s/cat/dog/g
• Replace once cat by dog s/cat/dog/
• Replace once on every line s/cat/dog/
• Replace all every line s/cat/dog/g
• Save the file w
• Save the file as w fileName
• Save and quit wq
• Merge a file into the current place r fileName
• Display line numbers set number
• Don't display line numbers set nonumber