1. The problem statement, all variables and given/known data:
Quote:
The ctrace facility expects its input code to conform to the language definition from the 1970's (Kernighan & Ritchie). This script's task is to help in adapting a C89 or C99 program to that syntax.
In particular:
Remove function prototypes, and remove type info from function headings.
Instead, the function arguments will be declared after the closing ) of the function heading, and before the opening { of the function body.
HINT: All the formal parameters in ANSI C have at least two words (a type name and parameter name) and all the formal parameters in K&R C have exactly one word (the parameter name). You can use that fact to identify a pattern, and then use sed's "t" command to repeat for additional parameters, until done.
NOTE: If a parameter is a pointer, the asterisk is part of the type, not the parameter name.
Remove declarations from within the headings of for loops, e.g.
for ( int i = 0; i < 10; i++ )
would no longer declare i to be 'int' here, but somewhere before the loop.
Try to move the declaration for for-loop counters to a new line immediately after the last '{'.
HINT: You can temporarily reverse a file and then use 'sed's pattern and hold spaces to hold the declaration until it is ready for insertion.
The results of this program script should appear on standard output (from which they can be redirected to a file). The resulting code must compile correctly in any C compiler.
2. Relevant commands, code, scripts, algorithms:
We have to do this using 'unix tools' and not use the script as if it were C. Meaning, he wants more uses of grep, sed, awk, cut, etc... than he does while, for, do's and done's.
3. The attempts at a solution (include all code and scripts):
We've done two other programs using these tools and I know how to use grep pretty well, but sed's so complicated that I'm not quite sure what method to use (and or why to use it) as this is our first major homework using it.
He said he was able to complete the homework in 2 lines of code using multiple pipes, but he didn't show us any of the code.
I'm assuming that I have to take something like this:
Code:
for (int i=0; i<10; i++)
{... }
and change it into:
Code:
for (i=0; i<10; i++)
{... }
int i;
and delete headers such as:
Code:
int func1(int a, int b...);
and change the actual functions to:
Code:
int func1(a, b...)
{ ... }
int a;
int b;
The deletions of the headers is pretty straight forward using sed:
Code:
sourcefile=$1
cat $sourcefile | sed "/^[a-zA-Z].* [a-zA-Z].*(.*);.*/ d" > newcode.c
First of all, am I interpreting his instructions correctly?
But where I don't know how to progress is the bigger picture. I don't have enough practice doing scripts such as these to know how to attack it. Can you give some help in crafting an attack at this? I'm not looking for the code but more the pseudocode.
4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):
Penn State University, PA, USA, Roger Christman, CMPSC311
I'm assuming that I have to take something like this:
Code:
for (int i=0; i<10; i++)
{... }
and change it into:
Code:
for (i=0; i<10; i++)
{... }
int i;
Not quite. The wording in your instructions, IMHO, uses a poor choice of words. I would have said to put the initialisation (int i) immediately following the previous opening curly brace. The word last obviously leads to incorrect interpretations as you did.
Thus, the resulting code would be:
Code:
{ /* beginning of current block */
int i;
for (i=0; i<10; i++)
{... }
Helping with home work is tricky, guiding without giving you the answer; I'll add more if I can figure how not to give you too much.
Last edited by agama; 10-05-2011 at 11:17 PM..
Reason: typo
That's what I thought too at one point. I couldn't be using i as a variable unless it was defined earlier. It didn't make sense to have it after the block of the function. The instructions are a direct cut from his assignment page.
But as I said, I'm not sure how he'll be grading it. He obviously wants us to use unix/linux tools as much as possible. However, the class is shell scripting so having working code is just as important, even if it's not as efficient as his code could be.
I don't know how to use the tools we have (sed, grep, cut, tr, etc...) to do this. That's more what I'm asking. How can normal command-line tools be used to do this? For instance, which tools can do this the best? substitution through sed? Do I need to use the hold buffer and pattern buffers extensively? I don't know how to attack the problem.
I've been arguing with this teacher the entire semester about what he's assigning and how he's assigning things. He's terrible, overall, and the class attendance (~18/60 daily) and average on the first homework (40/100) and the first exam (70/160) shows it. He's just not in touch with someone trying to learn it. For instance, this is our very first assignment in shell scripting. We learned awk but we're not allowed to use it (?) for the tabulated data program we had to do.
And as a result, I don't understand how to actually attack this problem. Do I treat the for loops separate from the other declarations of functions? And how do I use sed to manipulate a multiple line function? What if the function has the curly braces on the same line as the declaration? I have to take all this into account most likely. Is this how it would be done?
//use grep (or sed) to find a line with a function declaration
//search for the open parenthesis to the closed parenthesis and remember what's between them?
//call back the stored words as you write out a new line for each one?
Can all this be done in one pass of sed? This is where I'm lost. I don't know what's possible or not or how to go about approaching it.
Most commandline utilities are line-based, C is definitely not, so the first thing I'd do is try to transform C code into something more tolerable by stripping out whitespace and putting it exactly where I want. Many versions of sed don't work for lines longer than 2000 bytes though -- what system do you have?
Hi All,
Do you have any sample script,
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First:
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