Unix Shell Scripting

I'm sorry if this doesn't go here, but I'm in depserate need of help with my last unix homework.

Anyways, I'm taking summer classes, and one of them is UNIX. I've understood everything thus far, but I'm having a killer time with how my instructor has worded the problems for shell scripting. I thought this would be fairly easy seeing as I've done some c++, but everything I do doesn't seem to want to work.

the example my instructor gives me is this:

echo -n "Some argument "
echo $1

So to me it looks like this

cout << "Some argument"
cin >> argument

My assignment is to create a shell script that takes three arguments and then echos out "There once was a ___ that ____ who liked to ____" and the arguments go where the blanks go.

I've done multiple tries on this, but this is my latest attempt:

echo -n "There once was a "
echo $1
echo -n "that "
echo $2
echo -n "who liked to "
echo $3
echo -n "There once was a " $1 " that " $2 " who liked to " $3

There is a part 2 to the question, but if I get an understanding as to what I'm doing wrong I think I can figure out the rest of it.

The last question I have is for my final assignment. I have 150+ .txt files in a directory. These are my instructions:

-Do an LS and store the listings in a file
-Open the file in emacs.
-create a macro that converts that single line to the command "mv file.txt file.dat"
-run the macro over the entire file.
-chmod +x the listing file
-run the file as a script.

I put all the .txt files in new file called change. I went into emacs and made a macro where I searched for all .txt and then replaced them with .dat. I made the file executable, but I'm having a difficult time with the MV (move) command, is that suppose to be part of my marco? Or is it suppose to be text at the top of the page, something like this:

mv file.dat to file.txt?

Once again, I apologies if this isn't the correct thread, but I just had no idea what to do. Any help is appreciated also because my final is tomorrow, and I really just want to be able to understand what I'm doing wrong so I don't completely fail on this part of the final.

First, there are two flavors of the echo utility. The BSD-based version of echo concatenates all of the operands it is given and write them to standard output followed by a <newline>. If the -n option is present it doesn't output the <newline>. I assume this is the version of echo you have on your system. (On the UNIX System V-based version of echo -n is not an option; it is just another operand to be printed. But there are several escape sequences in the string operands that the System V echo will translate ("\t" -> <tab>, "\n" -> <newline>, "\0" -> skip the remainder of this and any following operand and skip the normal trailing <newline>, etc.) that the BSD echo will not change.) If you want to output some text without the normal trailing <newline> in a way that will be portable to all UNIX and Linux systems, use the printf utility instead of echo.

So, your cout << "string" being roughly equivalent to echo -n "string" is pretty close. But echo $1 is also an output statement; not an input statement. I'm more of a C guy, than C++. In C it is roughly equivalent to printf("%s\n", argv[1]); . The equivalence is would be exact if you used "$1" instead of $1 because if the string isn't quoted and you have the default setting for $IFS, any sequences of one or more <space> and <tab> characters will be translated to a single space and passed to the echo command as individual operands instead of as a single string.

In the shells (bash, ksh, sh, ...), $n (1 <= n <= 9) refers to the 9th argument given to to the shell script when it was invoked. If you use ${n}, n can be greater than 9. $0 refers to the name of the script (like argv[0] in a C or C++ program). So, if you have a regular file with the execute bit set named "script" that contains something like:

#!/bin/ksh
echo -n "There once was a "
echo $1
echo -n "that "
echo $2
echo -n "who liked to " 
echo $3
echo -n "There once was a " $1 " that " $2 " who liked to " $3

and invoked it as:

script man "spent a lot of time in a swimming pool" "win gold medals!"

the output should be something like:

There once was a man
 that spent a lot of time in a swimming pool
 who liked to win gold medals!
There once was a man that spent a lot of time in a swimming pool who liked to win gold medals!

This should not have been asked here. There is a dedicated homework forum. See item 6 @ Simple rules of the UNIX.COM forums:

Regards,
Alister

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