Introduction to UNIX

A User’s Perspective:Day 3: Advanced Commands & vi

What We Will Cover Today

Shell customizations File operation commands The UNIX search utility vi Shell script basics

Clean Up: Standard Error

Redirecting standard error– 2> = redirect standard error

Let’s redo the link example seen yesterday– cat file 2> errors– cat index.html 2> errors

BASH!

User friendly & Free Want to switch

– $ bash

Easy to navigate and edit at command-line– Let’s see…

Bash Tip 1

History recall– The up/down arrow

Korn Shell equivalent– $ set –o vi

Let’s you use vi control keys at the command-line

Bash Tip 2

Tab completion– Hitting the tab key will attempt to complete file name

from the current directory– Example

$ cd $ cd pu (hit the tab key)

Bash Tip 3

Remembering your history– Attempts to auto complete commands previously

entered– Start with CTRL-R– Start typing

Try ls -al

Bash Customization Ideas

Make you life easier Examples:

– $ alias procs=‘echo “Number of processes are: ”;ps | wc –l’ Issue the command ‘procs’

– $ procs

– $ alias ll=‘ls –al’– $alias l=‘ls’

These can be placed in your .profile so they are always available

Understanding Your Environment

env– Values that follow you when you change shells

set– Values set when you enter a shell– Lost when leave that shell

File Operations

join grep diff cmp dircmp split sed

join

cd cp –p /u/ux101is1/jointest* . sort –k 1 jointest1 > jtest1s sort –k 1 jointest2 > jtest2s join jtest1s jtest2s

– What are the issues?– What are possible resolutions?

grep

cd grep your_user_name /etc/passwd

– What did you find?

grep –i Filter *– What did you find?– What is the problem?

diff

cd diff jtest1s jtest2s

cmp & dircmp

cmp file1 file2– cmp jtest1s jtest2s

dircmp directory1 directory2– dircmp -ds public_html public_html/test > dircmp.txt

split

Example– $ split -l 1 jtest1s student– $ ls –al– $ cat student*

sed

Example:– cd– cp -p jtest1s sedtest– $ cat sedtest– $ sed -e 's/mark/mike/g' sedtest > sedtest1– $ cat sedtest1

Subshells

No change to your current shell state– ( some commands )– Example 1:

$ ( date; who ) > whowhen.txt

– Example 2: $ cd $ pwd $ ( cd pub*; pwd ) $ pwd

– Implications?

The UNIX Search Tool

find– Very versatile– Built in command

handling– Extremely extensible– Can be used to search

by any file characteristic

Advanced find

Example 1:

– find /u/msaba/public_html -type f -print | grep refs

Advanced find

Example 2:

– find /u/msaba/public_html -type f -print | grep refs 2> errors

Advanced find

Example 3:

– find /u/msaba/public_html -type f -print 2> errors | grep refs

Advanced find

Example 4:

– find . -name "*" -exec grep -i "ocks" {} /dev/null \;

find: Directory Tree Mapping

Show the directory hierarchy of /tmp– $ find /tmp –type f –o –print– $ find /tmp –type d –print

Making find More Efficient

A better way of invoking grep large number of files is: – $ find . -type f -print | xargs grep ocks – $ find . -type f -print 2> errors | xargs grep

ocks 2>> errors This results in far fewer invocations of grep

– Runs faster– Less system load

vi – The Only Editor You Need

Why learn vi?– You don’t always have a GUI interface– It’s on every UNIX system– It’s powerful– Try it, you’ll like it!

Let’s Edit Something

To create a new file– # vi new_file_name– # vi

To open a file for editing– # vi existing_file_name

Additional Modes for Starting vi

vi –r file– Recover the last saved version after a crash (rare)

vi –R file– Read-Only

vi +n file– Open with cursor at line number n

vi file1 file2 file3– Open multiple files, move between using :n

A Cool Feature of vi

:r– Reads into the current file the contents of a file

:r file

– OR– The output of a command

:r !command

Shell Scripts

The first line:– #!/usr/bash

The rest of the file:– Standard command sequences

A shell Script Example

cd public_html vi bash.script

– #!/usr/bash– cp –p /u/ux101fa*/jointest* /u/ux101fa*/public_html– sort -k 1 jointest1 > autojtest1s– sort -k 1 jointest2 > autojtest2s– join autojtest1s autojtest2s

$ . bash.script

What Should You Know?

How to Log on and off of a UNIX system Be familiar with UNIX shells Be familiar with the UNIX file system UNIX Paths, ownership and permissions Use UNIX commands Use vi Write a basic shell script

Question?

Anyone… anyone?

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