introduction to advanced unix 2010

8/3/2019 Introduction to Advanced UNIX 2010

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Introduction to Advanced

UNIXMarch 9 2010

Kevin Keay


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Outline

Overview Resources The basic form of a typical C-shell script Introduction to C-Shell Programming

Advanced UNIX materials: The following are PDF documents that may be used forreference but wont be discussed in detail during this short course:

Part 1 : ScriptsPart 2 :A summary of useful softwarePart 3 : Reanalysis products

Lab session (informal) 2-3 PM UNIX LabSee: http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdf
http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_1_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_2_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_3_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_3_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_2_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_1_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdf


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Overview

This is a practical course that is designedto give you the basic skills to write UNIX

C-shell scriptsYou can only truly understand the

concepts by putting them into practice!


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Overview (2)

We will look at the basic form of a C-shell script There will be a quick tour through Introduction to C-Shell

Programming

There are some extra advanced UNIX materials (Parts 1-3)that you may need to reference. Some aspects will belooked at during the lab session but they are intended forpersonal reference

Part 1 covers C-shell scripts and some additional concepts

Part 2 is a summary of some useful software Part 3 focuses on downloading and decoding reanalysisdata (NetCDF and GRIB)

Finally, there is a short Lab session


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Resources

A very useful and concise reference book covering UNIX and the C shell is:UNIX in a Nutshell, OReilly and Associates (Engineering Library: 005.43GILL).

A useful online resource from the University of Surrey, UNIX Tutorial forBeginners, is available at: http://www.ee.surrey.ac.uk/Teaching/Unix/

For PDF files of the handouts see:http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/

All UNIX commands should have a manual (man) page on the machine thatyou are using e.g. man awk. However sometimes the pages are not installed

or are in an unexpected location. It may be more convenient to use a searchengine like Google to find information on a command.
http://www.ee.surrey.ac.uk/Teaching/Unix/http://www.ee.surrey.ac.uk/Teaching/Unix/http://www.ee.surrey.ac.uk/Teaching/Unix/http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/http://www.ee.surrey.ac.uk/Teaching/Unix/


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The basic form of a typical C-shell script

The first line of a C-shell script (text file) is:#!/bin/cshf

Thef option tells the script not to source (read)the users .cshrc file; this is faster and also

makes the script more portable. All other lines starting with # are comments Commands may be continued onto subsequent

lines with \

Multiple commands can be placed on a singleline with ;

Spacesaround operators and commands are

required but there are no other restrictions


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The basic form of a typical C-shell script (2)

For neatness, end the script with exit (notessential)

Shell variablesstart with a $ (this is onlyomitted with using set or @ - see below) The shell variable $#argv contains the

number of arguments(items) typed onthe command line. The items are referredto as shell variables $1, $2, $3, , $#argv


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For example:myscript jja -4.56 yes

would give:

$#argv = 3

$1 = jja

$2 = -4.56

$3= yes


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Shell variablesare either string(text) or numeric A string variable is set (defined) by:set var = valuee.g. set x = Fred

Note: Variables and values are case-sensitive i.e.x is not the same as X

Variable names can be several characters e.g.set Case2 = 3

To print (display) the value of a variable:echo $vare.g. echo $xFred


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A numeric variable is set (defined) by:

@ var = integere.g. @ k = -7 Simple calculations may be performed

e.g. @ j = ($k + 1) [j would be 7 + 1 = -6]@ k = ($k + 1) would change k from -7 to -6Could also use C notation: @ k ++@ j = (2 * $k - 5) [k= -7 would give j= -19]Note: Put spaces around operators like *, + etc.

Floating point operations are not normally used in scripts

but can be done with the command bce.g. echo "2.1 + 6.3" | bcwould print 8.4 on the screenset y = `echo "2.1 + 6.3" | bc`would save the answer in variable y


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A shell variable may be given the outputof a command (or user program) as in thebc example. In general:

set var = `command`e.g. set ff = `ls *.dat`

Remember: ls is used to list files.

If the files are 5.dat 12.dat 13.dat thenecho $ffwould display:

5.dat 12.dat 13.dat


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The basic form of a typical C-shellscript (7)

To extract the individualelements ofvariable ff we can use $#ffto find the

number of items (similar to $#argv)e.g. echo $#ff would display 3

echo $ff[1] would display 5.dat

echo $ff[2] would display 12.datecho $ff[3] would display 13.dat


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A while loop is used to set up an iterative orrepetitive procedure:

while (condition is true)

commands

end

e.g. @ k = 1 # Initialise k

while ($k


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A foreach loop is used to set up an iterative orrepetitive procedure involving files:

foreach var (files)

commands

end

e.g. foreach f ([A-Z]*) # f is a file starting with a capital letter

echo $f # Print filename

mv $f $f.cap # Rename file to have extension .capend


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An if-else-endifstructure is used to control scriptbranching:

if (condition 1 is true)

commands

else if (condition 2 is true)

commands

else

commandsendif

Note: use else if notelseif


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e.g.if ($x == 6 || $s == sea) then

do something

else if ($x > 10) thendo something else

else

go here if neither of the above conditions is trueendif

Simpler or more complex forms are possible

e.g. if ($y == 2) lsl *.dat


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The while or if(condition) uses C notationfor logical operations:|| or

&& and

== equal>= greater than or equal

greater than

< less than


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An example#!/bin/cshf

if ($#argv != 1) then

echo Usage: myscript nameexit # If incorrect usage end the script

else # If only 1 argument, branch here

set n = ($1) # Put n equal to $1

endifecho Your name is $n

# You could do other things here

exit


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Another example

#!/bin/cshfset ff = `ls *.dat` # ff contains filenames *.dat@ nf = $#ff # nf equals the no. of files (items in ff)

@ j = 1 # Set counter j to 1

while ($j


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Introduction to C-shell programming

Refer to the PDF guide:http://www.earthsci.unimelb.edu.au/~kevin

/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdf
http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_C-Shell_Programming_2008.pdf


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Advanced UNIX materials

The following are PDF documents thatmay be used for reference but wont be

discussed in detail during this shortcourse:

Part 1 : Scripts

Part 2 :A summary of useful software

Part 3 : Reanalysis products
http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_1_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_2_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_3_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_3_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_2_2008.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Intro_to_Advanced_UNIX-Part_1_2008.pdf


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Lab session

Lab session (informal) 2-3 PM UNIXLab

See:http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdf
http://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdfhttp://www.earthsci.unimelb.edu.au/~kevin/UNIX_Course/Advanced_UNIX_Lab_Session_2010.pdf

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