Description
Overview:
Write a stream editor called svi. svi edits its standard input according to a list of edit
commands that are given in a file specified as the command line argument. The edited standard
input is output to standard output. Each line of input, and output after editing, will be maximally
256 characters long. (svi has many similarities with the standard UNIX utility sed.)
Edit Commands:
Each edit command consists of an optional line range specification, an edit operation specifier,
and data required by the edit operation. You may assume that all commands in command files
are correctly formatted.
There are three types of line range specifications:
/<text>/
This format specifies all lines that contain the <text>. The <text> can be maximally 80
characters.
<1st line number>,<last line number>/
This format specifies all lines in the range <1st line number> to <last line number>,
inclusive. Lines in the input file are considered to be numbered from 1, and this
numbering is not changed in the editing process.
No line range specification specifies all lines in the file.
There are five edit operations:
A<text>
Appends the <text> at the end of the line. For example:
Ahello jim
appends hello jim to all lines in the file. The <text> can be maximally 80 characters.
I<text>
Inserts the <text> at the start of the line. For example:
/blah/Ineedle noddle noo
inserts needle noddle noo at the start of all lines that contain blah. The <text>
can be maximally 80 characters.
O<text>
Inserts the <text> on a new line before the current line. For example:
1,1/OThe Title
Inserts a new line before the first line in the file, containing the text The Title. The
<text> can be maximally 80 characters. The new line is not put through the editing
process.
d
Deletes the line from the file. For example:
3,6/d
deletes lines 3 to 6 inclusive.
s/<old text>/<new text>/
Replaces the first occurence of <old text>, in the line, with <new text>. For
example:
/filename/s/.pas/.c/
replaces the first occurrence of .pas with .c, in all lines containing filename. The
<old text> and <new text> can be maximally 80 characters.
Data Structure
The edit commands must be stored in an array of structures, each edit operation being stored in
one element of the array. A maximum of 100 edit commands may be used. Each structure
contains four fields.
• Line range specification type – one of none, text, or line numbers. This must be an
enumerated type.
• Line range specification. Because there are three possible formats for the line range
specification, this field must be a union.
• The edit operation specifier.
• The data associated with the edit operation.
Overall Algorithm
Read in and store the edit commands from the file
Read a line from standard input
While not at EOF of standard input
For each edit command do
If the line is in the range specified then
Do the edit
Output the edited line (unless it has been deleted)
Read a line from standard input
Sample Run
If the file of edit commands is:
/Never done/I—————————————
1,3/IPrepended to 1,2 and 3 :
1,1/OThis must appear as the first line
A : Appended to all
/line for substitution/s/This is one/This has been substituted
on a/
9,10/d
/deleted/IThis should not appear
/Never done/I—————————————
and the standard input is:
1 To have text prepended
2 To have text prepended
3 To have text prepended
4 Unmodified except appended text
5 Unmodified except appended text
6 Unmodified except appended text
7 This is one line for substitution
8 This is one line for substitution
9 This is to be deleted
10 This is to be deleted
11 The last line of the file
then the standard output is: This must appear as the first line
Prepended to 1,2 and 3 :1 To have text prepended : Appended to all
Prepended to 1,2 and 3 :2 To have text prepended : Appended to all
Prepended to 1,2 and 3 :3 To have text prepended : Appended to all
4 Unmodified except appended text : Appended to all
5 Unmodified except appended text : Appended to all
6 Unmodified except appended text : Appended to all
7 This has been substituted on a line for substitution : Appended to
all
8 This has been substituted on a line for substitution : Appended to
all
11 The last line of the file : Appended to all
Submission
You must use the submit2 program to submit …
• Your solution source code
• Your makefile if you use one
• A README with anything you want the TA to know. In particular, if you do not succeed
in getting everything working perfectly, you should explain what is working, and what
you have achieved towards the aspects that are not working.
… with the command
~csc322/bin/submit2 csc322 StreamEditor <your file names>
by 11:59PM on December 10th.
Marks will be distributed as follows:
• Reading in the edit commands and building the data structure – 20%
o typedefed data structures – 9%
o Code for reading in from the file and extracting the commands – 11%
• Performance to specification – 50%
o Editing all lines with no line range specification – 5%
o Editing the correct lines with a text line range specification – 5%
o Editing the correct lines with a line number specification – 5%
o Simple edit commands (A, I, O, d) – 5% each = 20%
o Complex edit commands (s) – 15% each = 15%
• Programming style – 30% (Negative grading down to 0%)
o Formatting – 5%
o Comments – 5%
o Meaningful identifiers – 5%
o Functions and parameters – 5%
o (No) use of global variables – 5%
It is worth 15% of the course assessment.
