Description: The diff command line utility on UNIX and UNIX-based platforms compares two text files line by line and yields the difference if the files are not identical. The syntax is as follows:
diff [-options] file1 file2
The output of this utility typically outlines the minimal changes, in the form of three different type of instructions, that are to be made in file1 to make it the same as file2. For example, if the contents of the files are as shown:
| File1 | File2 |
| This is line one of file1 welcome code should execute This is a sample test case GNU is Not UNIX Linux is based on UNIX | This is line one of file2 welcome to UNIX tools code should execute 12345678987654321 This is a sample test case |
The output of 'diff file1 file2' would be:
| 1,2c,1,2 < This is line one of file1 < welcome ... > This is line one of file2 > welcoe to UNIX tools 3a4 >12345678987654321 5,7d5 < < GNU is Not UNIX < Linux is based on UNIX | Key things to note here: [1]. '<' indicates the lines of file1 and '>' indicates the lines of file2. [2]. 'c', 'd', 'a' refer to change, delete, and add respectively. These are the instructions that diff outlines. Numbers to the left and right of these instructions point to a line or range of lines from file1 and file2 respectively. [3]. '3a4' here means add line 4 of file2 after line3 of file 1. '5,7d5' means delete lines 5 through 7 from file1 to get a match up to line5 of file2. |
Notice that even if identical lines do not appear on corresponding line numbers of file1 and file2, diff proposes adjustments to their position in file1 through minimal changes, to match that of file2.
Assignment: For this assignment, a simplified version of the diff utility is to be implemented. This custom utility (which we will name csdiff) should function by only comparing the corresponding lines of the two text files provided as arguments (that is, without having to scan the files ahead to search and match lines). Rather than reporting a single line each time there is a difference, you should report deletions, additions, and changes grouped together like the diff utility.
Hence, if executed with the above files, output of'./csdiff file1 file should look like:
| 1,2c,1,2 < This is line one of file1 < welcome ... > This is line one of file2 > welcoe to UNIX tools 3a4 >12345678987654321 5,7d5 < < GNU is Not UNIX < Linux is based on UNIX | Assumptions and Restrictions: [1]. There will be at most 100 characters per line and at most 50 lines in the test case files of this assignment. [2]. All file operations should be implemented with the help of the relevant UNIX API calls. |
If the order of the files is reversed and provided to the custom csdiff utility, the change instructions remain similar, only the last instruction becomes:
5a6,7
>GNU is Not UNIX
>Linux is based on UNIX
It should be clear that for this custom implementation the addition and deletion instructions are only relevant when one of the files contains more lines than the other.
Command line options: The following options for the custom diff utility are to be implemented as described :
-d The presence of this option would require the implementation to delete the least recently modified file in case the two provided files are identical.
-o file The presence of this option implies that the output of the utility is to be written/redirected to the file instead of standard output.
Exit Code: The csdiff utility should exit with EXIT_SUCCESS if the files are identical and EXIT_FAILURE otherwise (files could not be opened or they differ).