Homework & Coursework Questions

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1. The problem statement, all variables and given/known data:
1) The script is executed in the Korn shell.
2) Name the shell script file is asg6s.
3) The asg6s file is executable and accepts exactly two arguments from the command line.
4) The asg6s file accepts any two named files as the two arguments that are text files.
5) Create a file containing “Message Holder” as the text within the file. This file is entered on the command line as the first argument.
6) The second argument is a file with whatever name you select that accepts the output from the asg6s file.
7) The command line must have the following: asg6s [input file name] [output file name] before any processing can occur. The input file must contain the words detailed in 5) above. The output file is created at the time the command line is executed, not before.
8) The script first checks that there are exactly two arguments on the command line. If the command line does not have two arguments, display an error message that includes a suggestion of the pattern on the command line and exit the script.
9) If the condition in 8) is met, then the script must independently check that the file named by the first argument both exists and contains some text. If the command line does not have as its first argument a file that exists and contains some text, display an error message that includes the name of the file and exit the script.


2. Relevant commands, code, scripts, algorithms:

Command line argument

Hello I am having a lot of trouble understanding for one, what I am supposed to do and two how I am supposed to implement this.

Obviously I am missing something. I think the main thing is I am not setting up the file to accept only two arguments from the command line. Any help would be appreciated. Even if it is links to help me understand what I am not understanding. Thanks

3. The attempts at a solution (include all code and scripts):

Code:

#!/bin/ksh
#Reroute to directory of used files
cd /class/
#Make the asg6s accept only two arguements
if [[ $# -ne 2 ]];then
    print "Does not equal two arguments"
    exit
fi
#Creates file containing Message Holder
cat message
Message Holder
#File that accepts the output of file message
cp message message1
#Determine if first argument is empty or null
if [ -z "$1"]
    echo "File does not exist"
fi

4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):

University of Maryland University College
3501 University Blvd. East
Adelphi, MD 20783

CMIS 325 6380 UNIX with Shell Programming (2152)

Professor: Thomas Timko

You seem to have an issue creating that text file.
See man ksh section "Redirection". (i assume its named the same as in man bash)

Just for the habbit, inconsistent use of single and double brackets for condition checking.
In BASH, the official standard (POSIX) is to use single brackets, eventhough double brackets work just quite as good on some systems it doesnt on others.
I assume the same for KSH, so i would recomend to use only single brackets, precicly as you done (incl the quoting) in the last if block.

Which besides is missing its 'then' part.
Maybe this fixes something?

Hope this helps to get you started.

Also your references the first positional parameter, but not the second one. Otherwise lookup "positional parameters" in "man ksh" .

There is also a space issue with testing if the variable $1 is empty.
Obviously an empty string cannot exist as a file, but assuming a file exists only because a variable contains something can lead to unexpected behaviour.

In addition to what sea and Scrutinizer have already said, also note that there must be spaces between the arguments to the test expression command (AKA [ expression ]), including the closing ].

Also look at the man page for the cat command (man cat). You can use cat to put text into a file, but not the way you have done it. The text to go into your output file needs to be fed into cat by piping data into cat, redirecting input from a file containing the text, using a here-document, or naming the file containing your input data as a file operand. You might also consider redirecting the output from a Korn shell echo or printf built-in command to put a line of text into a file using redirection.

You have set up your script to be run by the Korn shell and checked that there are exactly two arguments given to your script. That takes care of items #1 and part of #3 in your assignment.

We can't tell what you have named your script nor whether or not you have made it executable from what you have shown us.

I don't see anything in your assignment that says that a file named message exists in your assignment directory nor that you are supposed to create a file named message1.

ok I made some progress:

Code:

 
 #!/bin/ksh
 #Reroute to directory of used files
 cd /class/
 #Create function to handle exit function
 function usage{
 echo "Usage $0 inputfile outputfile"
 echo "The inputfile must have the text \"${must_have_text}\""
 exit 1
 }
 #Make the asg6s accept only two arguements
 if [ $# -ne 2 ]; then
 echo "Does not equal two arguments"
 usage
 fi
 #Creates file containing Message Holder
 #Have a variable for the message
 must_have_text="Message Holder"
 #Determine if first argument is empty or null
 #Create variables
 infile=$1
 outfile=$1
 if [ ! -f "${infile}"]; then
 echo "File ${infile} does not exist"
 usage
 fi
 if [ $(grep -c "${must_have_text}" ${infile}) -eq 0; then
 echo "${infile} must have 1 or more times the text ${must_have_text}"
 usage
 fi
 cp ${infile} ${outfile}

I keep getting this error though: ./asg6s: line 3: syntax error at line 6: `echo' unexpected

Hi,

Look at the syntax:

Code:

function varname { list ;}

There is a space between the varname and the opening brace.