CSC230-Project 3 Line/Column Removal Program Solved

On Unix systems, there’s a shell command called cut. It’s handy for extracting selected columns from a text file

(i.e., discarding everything but a chosen range of columns). We’re going to write our own program kind of like cut, except our program will be able to remove individual lines and columns from a text file, as well as ranges of lines and columns.

Our program will be called chop (a name kind of like the original cut). You can run it on any text file, but it’s made to run on files like the following, with fields organized into well defined rows and columns. This example is a copy input-b.txt from our test inputs.

        Name  Sec  Gr   Verb  Quant  Logic  X 

       Young  003   3  89.81  67.10  80.85  D 

       Venus  002   8  72.29  73.59  76.20  A 

      Jasmin  003   6  55.19  50.51  63.88  F 

     Micheal  001   3  98.93  91.37  99.00  C 

       Abram  001   2  50.23  90.14  57.36  E 

   Rigoberto  002   8  61.63  94.64  77.05  B 

         Noe  003   2  68.41  61.79  64.60  A 

     Kristin  002   5  77.34  84.68  65.16  B 

     Phillip  001   6  63.19  76.08  52.39  B 

     Monique  001   6  81.76  57.62  80.15  A 

       Verda  002  10  93.03  56.21  93.58  C 

      Louise  003   2  70.30  71.37  61.91  C 

       Vilma  001   9  71.09  93.43  76.72  G

When you the program, you give it command-line arguments to tell it what to do. The arguments start with an (optional) series of commands for what lines and columns of the file to discard. For example, if your run it as follows, you’re telling it to discard the first line, then discard columns 13 through 17 (the column labeled Sec at the top), then discard lines 3 through 5, then discard column 2 (a column of space to the left of the names). ./chop line 1 cols 13 17 lines 3 5 col 2 input-b.txt output.txt

The last two command-line arguments give the input file name and the output file name. Here, we’re telling the program to read from a file named input-b.txt and write to an output file called output.txt. Run like this, the program should produce an output file containing the following, a copy of the text from the input file, but with the selected lines and columns removed.

      Young   3  89.81  67.10  80.85  D 

      Venus   8  72.29  73.59  76.20  A 

  Rigoberto   8  61.63  94.64  77.05  B 

        Noe   2  68.41  61.79  64.60  A 

    Kristin   5  77.34  84.68  65.16  B 

    Phillip   6  63.19  76.08  52.39  B 

    Monique   6  81.76  57.62  80.15  A 

      Verda  10  93.03  56.21  93.58  C 

     Louise   2  70.30  71.37  61.91  C 

      Vilma   9  71.09  93.43  76.72  G

As in project 2, you’ll be developing this project using git for revision control. You should be able to just unpack the starter into the p3 directory of your cloned repo to get started. See the Getting Started section for instructions.

This homework supports a number of our course objectives. See the Learning Outcomes section for a list.

Requirements
 

You’re going to write a program, chop, that allows the user to discard selected lines and columns from an input file and write the resulting text to an output file. You can also ask the program to read from standard input and write to standard output if you want.

Command-Line Arguments
 

Input and Output
 

The chop program can take differing numbers of command-line arguments, but the last two arguments always describe the input file then the output file. So, if you run the program as follows, you’re asking for it to read text from input.txt and write its output to output.txt:

$ ./chop input.txt output.txt

Instead of giving a filename for input or output, you can give a dash instead, to tell the program to read input from standard input or write output to standard output. For example, i run as follows, the program will read from standard input, but write output to a file named output.txt.

$ ./chop - output.txt

Or, you can tell it to read input from a file and write output to standard output. $ ./chop input.txt - 

Or you can read and write to the standard streams if you want:

$ ./chop - - 

If the user specifies a file that the program can’t open, it should print the following message to standard error (where filename is the name of the file given on the command line), then terminate with an exit status of 1. You’ll need to try to open the input file before the output file, so if both files are bad, the error message should be for the input file.

Can't open file: filename

Because of how the text will be stored, there’s a limit on the length of lines in the input and on the maximum number of lines in the input. Lines can be at most 100 characters long (not counting the line terminator at the end or the null terminator used to store the line as a string). If the program is given an input file with a line that’s too long, it will print the following message to standard error and terminate with an exit status of 1.

Line too long

The input file can’t have more than 10,000 lines. If the program is given a file with too many lines, it will print the following message to standard error and terminate with an exit status of 1.

Too many lines

Line and Column Removal Commands
 

The program should write to the output file a copy of the text from the input file, possibly with some lines and columns removed.

Before the input and output file names, the user can specify any number of commands for removing lines and columns from the file. Each command is given as either two or three consecutive command-line arguments. The program can handle four different types of commands:

  line n

Remove line number n from the text before writing it to the output file. Subsequent lines (if there are any) should be moved up to fill in the space.

  lines n m

Remove all the lines from line number n up to and including line number m. Subsequent lines (if there are any) should be moved up to fill in the space.

  col n

Remove the character from column n from every line of the file. Subsequent characters on each line should be moved left to fill in the space.

  cols n m Remove all the characters from column n up to and including column m from every line of the file. Subsequent characters on each line should be moved left to fill in the space.

For command-line arguments, all the line and column numbers count from one as the number of the top-most line or the left-most column.

The user can put any number of commands on the command-line, one after another. The requested removals should be done in order. For example, the following command will remove line 2 then line 4 from the input text.

chop line 2 line 4 input.txt output.txt

Order matters here. As shown below, removing line 2 moves subsequent lines up. If we remove line 4 next, that’s the same line that started out on line 5, but got moved up a line when line 2 was removed. If you did these two commands backward (removing line 4 then line 2), you’d get a different result.

 

Removing line 2 then line 4

On the command line, if the user gives an invalid value for one of these numeric arguments (e.g., a zero, a

negative value or just garbage), your program should print the following error/usage message then terminate with an exit status of 1.

invalid arguments usage: chop command* (infile|-) (outfile|-)

For the commands that take a range of line or column numbers, it’s OK if the start and end of the range are identical, that’s not an error. However, the end of the range can’t be before the start. For example, the following would be invalid arguments and your program should respond the same way as the above.

chop cols 7 3 input.txt output.txt

It’s OK if the user tries to remove lines or columns that aren’t actually there in the input. The program should remove text that’s within the request range of lines and columns, but it shouldn’t complain if some of the requested lines don’t exist or if some parts of the file don’t have any characters in the the given range of columns. The program should just remove the lines or columns that are actually there.

For example, the following command tries to remove lines 5 through 8.

chop lines 5 8 input.txt output.txt

If you use this on a file that’s just six lines long, it should just remove the last two lines (the lines that are inside the range of lines the user asked us to remove). It’s not considered an error if the user gives us a range that extends beoynd the last line of the file.

 

Removing lines within the given range

This behavior is even more important when removing columns, since different lines may have different lengths. Depending on the input, it’s possible some lines of the text will have characters inside a given range of columns, but others may be too short.

For example, the following command is a request to remove columns 3 through 5.

chop cols 3 5 input.txt output.txt

If you run this command on the following text, some short lines will be unaffected, they don’t have any characters between columns 3 and 5. Some lines may be truncated (here, if they’re between 3 and 5 characters long). For longer lines, some of the characters off to the right will have to be moved to the left to fill in the part of the line that was removed. This is what has to happen for the line that says “Example”.

 

Removing columns from a file with irregular line length

Design
 

The chop program will be defined in three components:

  text.c and text.h

This component defines the array of strings used to represent lines of text from the input file. It also has functions to read this representation from a file and write the resulting text out to a file.

  edit.c and edit.h

This component contains functions to edit the contents of the text representation, specifically to remove one or more lines and one or more columns.

  chop.c

This is the main component of the program. It will parse the command line arguments, open the input and output files and use the other components to read the input, remove selected lines and columns, then right out the resulting text.

Text Representation
 

The text will be represented using global variables. You’ll store it as a 2D array of characters, with each row of the 2D array storing a (null terminated) string containing a line of text from the input. Remember, that lines from the input can be up to 100 characters long (not counting the line terminator at the end), so you’ll need to make sure your 2D array is wide enough. In your text representation, you can choose to either store the line termination at the end of the line, or leave it out of the representation and just add it back in when you’re printing the output. It’s up to you.

The input can contain up to 10,000 lines of text, so your 2D array will need enough rows to store a file this big. These dimensions would be a good think to represent with preprocessor constants. You’ll probably need to use them in more than one place.

In addition to the 2D array containing the text from the input, you’ll need another global variable for storing the number of lines in the input. You can define both of these variables in the text.c component, with external declarations in the text.h header so other components can access them.

Global Variables
 

Don’t use any global variables other than the two you’ll need to represent the text from the input. Everything else you should be able to get from the parameters passed between your functions.

Functions
 

You’ll implement and use the following functions, to break the program into smaller components and to help simplify main(). Functions that are defined in one component and used in another should be prototyped (and documented) in the header.

  void readFile( FILE *fp )

This is part of the text component. I reads text from the given file and stores it in the global text representation. If the program reading from standard input, then the given file pointer will be stdin.

  void writeFile( FILE *fp )

This is part of the text component. It writes out the text from the global text representation to the given

output file. If the program is writing to standard output, then the given file pointer should be stdout.

  void removeLines( int start, int end )

This is part of the edit component. It modifies the global text representation to remove lines in the given range. You can use it to remove just one line by giving it a range that’s just one line long. You can choose exactly how you want these begin and end values to work (e.g., are the same values given on the command line, or would you rather have them count from zero for the internal workings of your program. This function would be a good place to use the strcpy() function we talked about in class. It could help to copy lines around the text array, to fill in the space left by removing one or more lines.

  void editLine( int lno, int start, int end )

This is part of the edit component. Its job is to remove characters in the start .. end range on just one line (the one at index lno). As with removeLines, you can choose exactly what you want to do with the three parameters (e.g., do you want them to count from zero or from 1). In my own solution, this was probably the most difficult function for me to write. As you develop it, you may want to write a little test driver to let you test it on particular cases. Then, once you’re sure it’s working, you can start using it from the rest of your program. When this function has to move characters within a line of text (to fill in the gap left by removing some columns), you should not use strcpy() for this. It’s not guaranteed to work if the source and destination strings overlap. You can either write your own code to hadle this, or you can do it with memmove().

  void removeCols( int start, int end )

This is part of the edit component. It uses the editLine() function to remove the given range of columns from all the lines of the text. In my solution, this function was pretty simple.

You can add more functions if you need them. If you define any functions that are only used within a single component, mark them as static so they won’t pollute the global namespace.

Magic Numbers
 

Be sure to avoid magic numbers in your source code. Use the preprocessor to give a meaningful name to all the important, non-obvious values you need to use. For example, you can define constants for the maximum length of a line of text or the maximum number of lines in the input.

For constants that are explained right in the line of code where they occur, I wouldn’t call these magic numbers. For example, if you need to read two integers, you might write something like the following. Here, the value 2 wouldn’t be considered a magic number. It’s explained right there in the format string, where we say we’d like to parse two integers.

    if ( fscanf( stream, "%d%d", &a, &b ) != 2 ) { 

        .... 

    }

When you’re parsing command-line arguments, you’ll be writing similar code, using small offsets to look around at nearby command line arguments, something like:

    if ( strcmp( argv[ currentArg ], "albus" ) == 0 &&          strcmp( argv[ currentArg + 1 ], "severus" ) == 0 &&          strcmp( argv[ currentArg + 2 ], "minerva" ) == 0 ) { 

        .... 

    }

Here also, you can use small literal values for fixed offsets into the list of command-line arguments. I don’t think there’s much to be gained by having a constant like “ARGV_ONE_AHEAD”. However, be sure to take advantage of opportunities for reasonable constants. For example, it’s probably worth something to have a constant for the number of required command-line arguments. You’d probably use this constant in lots of places when you’re parsing the arguments.

Build Automation
 

You get to create your own Makefile for this project (called Makefile with a capital ‘M’, no filename extension).

Its default target should build your program, compiling each source file to an object file, then linking to produce an executable. Your Makefile should correctly describe the project’s dependencies, so if a source or header file changes it rebuilds just the parts of the project that need to be rebuilt.

Your Makefile should also have a clean target that deletes any temporary files made during build or during tests (e.g., executables, objects, program output). A clean rule can look like the following. It doesn’t have any prerequisites, so it’s only run when it’s explicitly specified on the command-line as a target. It doesn’t actually build anything; it just runs a sequence of shell commands to clean up the project workspace. Your clean rule will look like the following (we used the <tab notation to remind you where the hard tabs need to go). In your clean rule, replace things like all-your-object-files with a list of the object files that get built as part of your project.

clean: 

<tabrm -f all-your-object-files 

<tabrm -f your-executable-program 

<tabrm -f any-temporary-output-files 

<tabrm -f anything-else-that-doesn't-need-to-go-in-your-repo

To use your clean target, type the following at the command line, but first be sure you are not deleting anything that you need, as the -f flag forces the removal without asking you if it’s OK. You may want to try it first without the -f flag to be sure it is deleting the correct files.

$make clean

Testing
 

The starter includes a test script, along with test input files and expected outputs. When we grade your program, we’ll test it with this script, along with a few other test inputs we’re not giving you. To run the automated test script, you should be able to enter the following:

    $ chmod +x test.sh # probably just need to do this once     $ ./test.sh

This will automatically build your program using your Makefile and see how it behaves on the test inputs.

You probably won’t pass all the tests the first time, and the test script won’t work until you have a working Makefile. Until then, you can run tests yourself. You can use a command like the following to compile your programs (although your Makefile will be more efficient, compiling source files separately and then linking them together):

$ gcc -g -Wall -std=c99 chop.c edit.c text.c -o chop

If you want to try your program out on one of the provided test cases, you can enter commands like the following. Here, we’re doing the same thing test 3 does from the test script. We’re running the program with input-a.txt as input. We’re telling it to write the output to a file named output.txt and to capture standard output and standard error to two different files. On the command line, we’re telling it to cut out most of the columns from the middle. After running the program, we check its exit status (should be zero for this test, which it is). Finally, we compare the program’s output against the expected output.

$ ./chop lines 2 25 input-a.txt output.txt stdout.txt 2 stderr.txt 

$ echo $? 

0 

$ diff output.txt expected-03.txt

Test Inptus
 

We’ve prepared several test cases to help you make sure your program is working right. These depend on a few different input files:

 input-a.txt is contains a square grid of letters, with a copy of the whole alphabet on each line.

input-b.txt is a file with fields organized into rows and columns.

input-c.txt is a list of color names with their RGB values, derived from an X11 color database on Wikipedia.

 input-d.txt is a file that’s not organized into uniform columns. It’s just a bunch of text, with some lines longer than others. input-e.txt has a line that’s more than 100 characters long. It’s used for an invalid test.

input-f.txt has more than 10,000 lines. It’s used for an invalid test.

The test cases use these few input files to try out different features in your program:

1.      This test uses input-a.txt. It makes no changes to the text, writing out an output file that should look just like the input.

2.      This test uses input-a.txt. It uses the line command to remove line three from the text.

3.      This test uses input-a.txt. It uses the lines command to remove lines 2 - 25 from the text.

4.      This test uses input-a.txt. It uses the line command twice to remove the top two lines from the text.

5.      This test uses input-b.txt. It uses a few line and lines commands to remove selected lines from the text.

6.      This test uses input-a.txt. It uses the col command to remove column number 3.

7.      This test uses input-a.txt. It uses the cols command to remove columns 2 through 25.

8.      This test uses input-a.txt. It uses the col command twice to remove the first two columns.

9.      This test uses input-b.txt. It uses a few different col and cols commands to remove several selected columns.

10.  This test uses input-b.txt. It’s the same as the example given at the start of this assignment, using a combination of all four types of commands to remove selected lines and columns from the input file.

11.  This test uses input-c.txt. It uses several commands to delete lines and columns from the input.

12.  This test uses input-a.txt. It uses the lines command to try to remove a range of lines that extends beyond the end of the file. This is OK. It should only affect the lines that are not in the range.

13.  This test uses input-a.txt. It uses the cols command to try to remove a range of columns that extends beyond the right edge of the block of text. This is OK. It should only remove text that’s actually inside the given range.

14.  This test uses input-d.txt. It uses the col and cols command to remove columns that have characters on some lines, but are out past the end (or partially out past the end) of other lines.

15.  This test uses the dash character to read from standard input rather than from a given file.

16.  This test uses the dash character to write to standard output rather than from a given file.

17.  This is a test of invalid input. We are using an input file that contains a line that’s too long.

18.  This is a test of invalid input. We are using an input file with too many lines.

19.  This is a test of invalid input. We are asking the program to open an input file that doesn’t exist.

20.  This is a test of invalid input. We are not giving a legal command in the command line arguments.

21.  This is a test of invalid input. We are giving a bad range of numbers for the cols command.

This is a test of invalid input. We are giving a string that doesn’t parse as an integer for the lines command