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# 1  
Old 02-19-2008
significance of statement

Hi,
I am a newbie in unix shell scripting and I am trying to understand the result of the following line :

ls -l $1*$4*ready

I understand the ls-l but the rest is just really confusing. Any help would be appreciated.
TIA
# 2  
Old 02-19-2008
The script gets several parameters on the command line, the first one is "$1" inside the script, the second one "$2", etc. Here is an example for that mechanism:

Code:
user@machine:/~ # cat showparams.ksh

#! /usr/bin/ksh

print - "1st parameter: $1"
print - "2nd parameter: $2"
print - "3rd parameter: $3"
print - "4th parameter: $4"
exit 0

user@machine:/~ # ./showparams.ksh a b c d
1st parameter: a
2nd parameter: b
3rd parameter: c
4th parameter: d

By the way (this is not answering your question, but probably not wasted on a scripting beginner either): it is NOT good programming style to use these parameters as they are! Usually these parameters have some "meaning" in your script and it is better to define some variables, check the parameters if they make sense and then copy the commandline parameters to these variables and use them.

Here is an example. The script does nothing useful, just takes three parameters, an input file, an output file and a number and copies the content of the input file to the output file prepending every line with "Value was <number> ;". Its purpose is just to show hoe to first check and then subsequently use parameters passed on the command line.

Code:
#! /usr/bin/ksh

typeset    fInput="$1"            # file with the data to work on
typeset    fOutput="$2"           # file to store results to
typeset -i iSomeValue=0           # some numerical value

# before we use the parameters we test if they make sense:

                                  # make sure input is readable
if [ ! -r "$fInput" ] ; then      
     print -u2 "File $fInput is not readable or does not exist."
     exit 1
fi   

touch "$fOutput"                  # make sure output is writable
if [ $? -gt 0 ] ; then
     print -u2 "File $fOutput is not writeable."
     exit 1
fi
     
                                  # make sure $3 is really an integer
if [ -z "$(print - "$3" | sed 's/[0-9]//g')" ] ; then
     print -u2 "The third parameter must be integer, you entered $3"
     exit 1
else
     iSomeValue=$3
fi

# .... here goes the rest of your code ...

cat $fInput | while read chLine ; do
     print "Value was $iSomeValue ; $chLine" >> $fOutput
done

exit 0

To test this script create a file "inputfile", put some lines of text into it and call the script with

Code:
./script.ksh inputfile outputfile 25

which will work. Try

Code:
./script.ksh inputfile outputfile erroneous_value

then and it will fail with the error message:

The third parameter must be numeric, you entered erroneous_value.

I hope this helps.

bakunin
# 3  
Old 02-19-2008
Thanks for your help

Thank you for your detailed response. I appreciate your time and it looks like I have a long ways to go before I am going to be able to write effective scripts. Would you be able to recommend textual material I could reference through this learning process ?
Thanks again
# 4  
Old 02-19-2008
Quote:
Originally Posted by nickcarter
Thank you for your detailed response. I appreciate your time and it looks like I have a long ways to go before I am going to be able to write effective scripts. Would you be able to recommend textual material I could reference through this learning process ?
Thanks again
Glad to be of help and: Yes! Get a copy of Barry Rosenbergs "Hands-On ksh93 programming", it is not only full to the brim with information (i use it as my desk-side reference wherever i go) but also a great fun to read. It is by far the best read i ever encountered as an IT-book.

bakunin
 

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