London | Ameneh Keshavarz | Implement-shell-tools| WEEK3 #49
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Thank you for your PR! I'm Borja, a volunteer, and I'll be reviewing your code.
The implementations of cat, ls and wc are good! I have left a few edge cases that are not covered, as well as a few suggestions, but you're definitely on the right track :)
Besides that, would you mind including the package.json and package-lock.json files you used during development? For a stretch goal, could you tell me why we should or shouldn't commit them to a repository?
Keep up the good work!
implement-shell-tools/cat/cat.js
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| //const nOption = program.opts().number; | ||
| //const bOption = program.opts().number2; |
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Do we need to keep these lines around? They seem to be doing the same thing as the next line.
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Thanks, I removed the unnecessary commnets.
implement-shell-tools/cat/cat.js
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| try { | ||
| const content = await fs.readFile(path, { encoding: "utf-8" }); | ||
| const lines = content.split("\n"); | ||
| if(lines[lines.length - 1] === "") { |
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| if(lines[lines.length - 1] === "") { | |
| if (lines[lines.length - 1] === "") { |
In other parts of the code, there is a space between the if and the opening parenthesis, so we should be consistent. This is purely a style comment, and doesn't affect the correctness of the program.
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Yes, I updated the code to be consistent.
implement-shell-tools/cat/cat.js
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| if (nOption) { | ||
| console.log(`${lineNumber++} ${line}`); | ||
| } else if (bOption && line.trim()) { | ||
| console.log(`${nonEmptyLineNumber++} ${line}`); |
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There seems to be something wrong with the output. When I run this code, the lines on multiple files are counted the with the same counter:
$ node cat.js -b sample-files/*.txt
1 Once upon a time...
2 There was a house made of gingerbread.
3 It looked delicious.
4 I was tempted to take a bite of it.
5 But this seemed like a bad idea...
6 There's more to come, though...
However, when we run cat, we can see that every line number is counted individually:
➜ cat -b sample-files/*.txt
1 Once upon a time... # From sample-files/1.txt
1 There was a house made of gingerbread. # From sample-files/2.txt
1 It looked delicious. # From sample-files/3.txt
2 I was tempted to take a bite of it.
3 But this seemed like a bad idea...
4 There's more to come, though...How can we modify the code so that the lines are counted correctly?
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Thanks for the feedback. I checked my code, and the issue was that I expected line numbers to reset for each file. But the real cat -b also keeps numbering across multiple files without resetting. I've updated my script, and it now matches that behavior.
implement-shell-tools/cat/cat.js
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| function printLinesWithOptions(lines) { | ||
| lines.forEach((line, index) => { | ||
| if (nOption) { | ||
| console.log(`${lineNumber++} ${line}`); |
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What happens when lineNumber goes into double-digits? In cat, it keeps alignment:
$ cat very_long_file
...
10 .parse(process.argv);
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Yes, line numbers were misaligned. Fixed it using padStart() to align them like cat -n.
implement-shell-tools/cat/cat.js
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| try { | ||
| const content = await fs.readFile(path, { encoding: "utf-8" }); | ||
| const lines = content.split("\n"); | ||
| if(lines[lines.length - 1] === "") { |
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Why do we need this special case?
Furthermore, what happens if lines is empty? I know that, because of how split works, you'll always get at least one element, but as the code evolves, this may no longer be true.
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Thanks, the special case isn’t strictly necessary, but I included it to be safe in case the input source changes in the future. I’ll also make sure to handle potential empty results from split() to avoid issues as the code evolves.
implement-shell-tools/ls/ls.js
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| if (onePerLine) { | ||
| files.forEach(file => console.log(file)); | ||
| } else { | ||
| console.log(files.join(' ')); |
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In ls, files are printed with a certain amount of padding, so that if we have many files, they appear to be in a table:
➜ /bin/ls
ls.js package-lock.json README.md
node_modules package.json sample-files
This is not part of the assignment brief but, as a streacth goal, would you like to consider how to pad the outputs like that?
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| program | ||
| .description('Count lines, words, and characters in the specified files') | ||
| .option('-l, --lines', 'Count the lines') |
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When counting lines, your program counts one more than wc:
➜ wc -l sample-files/3.txt
5 sample-files/3.txt
➜ node wc.js -l sample-files/3.txt
6 /Users/blorente/code/github.com/CodeYourFuture/Module-Tools/implement-shell-tools/wc/sample-files/3.txtWhy does this happen? How could we fix it so that we print the right number of lines?
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I was using data.split('\n').length, which overcounts lines. To match the behavior of wc -l, I updated it to:
const lines = (data.match(/\n/g) || []).length;
implement-shell-tools/wc/wc.js
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| const lines = data.split('\n').length; | ||
| const words = data.split(/\s+/).filter(Boolean).length; |
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This section of the code is processing data twice: Once to split it into lines, and another one to split it into words. While this is correct, in very large files, this could potentially be quite slow.
Is there a way we could avoid processing the entirety of data twice?
This is a stretch goal, as the current program is already correct.
implement-shell-tools/wc/wc.js
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| if (options.lines !== false) totals.push(totalLines); | ||
| if (options.words !== false) totals.push(totalWords); | ||
| if (options.characters !== false) totals.push(totalCharacters); |
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Why did you add the !== false clause to these lines? Is there any way we could express the same in a more concise way?
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The !== false checks were overly cautious, siince commander sets options to true or undefined, the concise and correct way is simply:
if (options.lines)
| .option('-l, --lines', 'Count the lines') | ||
| .option('-w, --words', 'Count the words') | ||
| .option('-c, --characters', 'Count the characters') | ||
| .parse(process.argv); |
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Your solution prints the full path of each file:
➜ node wc.js -l sample-files/3.txt
6 /Users/blorente/code/github.com/CodeYourFuture/Module-Tools/implement-shell-tools/wc/sample-files/3.txtWhereas wc only prints the path relative to the directory we run it from:
➜ wc -l sample-files/3.txt
5 sample-files/3.txtHow would you modify this code to print the relative path?
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I was printing the absolute path using path.resolve, which made the output differ from wc. I’ve updated the code to print the original file argument instead, so it now shows the relative path the we type.
blorente
added
👀 Review Requirements
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Hi Borja, Thanks for the feedback and for reviewing my code! I looked at the edge cases you mentioned and add the package.json and package-lock.json files. We should commit both files because: package.json shows what packages the project needs. package-lock.json makes sure everyone installs the exact same versions. Thanks again |
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