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I wrote marcel. In my view, nushell and marcel are very similar. nushell has tabular output, which I haven't thought was all that useful. Marcel is python-base
by geophile 3y ago
I wrote marcel. In my view, nushell and marcel are very similar. nushell has tabular output, which I haven't thought was all that useful.
Marcel is python-based. The nushell guys have had to invent a lot of language. By basing marcel on python, I don't have to invent language. Any logic to be added is expressed in python. E.g, do a recursive listing of files and find those that changed in the last 3 days:
ls -fr | select (f: now() - f.mtime() <= days(3))
The stuff inside the parens is a python function, applied to a File f, piped in from ls. (Marcel lets you omit "lambda".)
Lots of marcel examples here: https://marceltheshell.org https://marceltheshell.org
- mito88 3y agomarshell the cell.... sorry couldn't resist. :)
- js2 3y agoThis looks interesting, but the examples don't really show off Marcel's power. The example you just gave without Marcel is: find . -type f -mtime -3 The example on this page: https://www.marceltheshell.org/list-processes https://www.marceltheshell.org/list-processes ps -u djt | map (p: p.signal(9)) That's: pkill -9 -u djt The example for summing files by extension is a bit more interesting: ls -fr | map (f: (f.suffix, 1)) | red. + | sort Vs something like: find . -type f | awk -F. '(NF>1){print "."$NF}; (NF==1){print ""}' | sort | uniq -c That said, every time I look into one of these shells, I end up sticking with bash. When it gets to the point that I need something more powerful than bash and the Unix command line environment, I'd just as soon write a stand-alone program which I can check into version control, use on remote systems that don't have one of these fancy shells installed, add proper tests, etc. This is a neat project though. I'll keep an eye on it.
- geophile 3y agoI actually agree with most of this. I tend to use Marcel for ETL sorts of processing, quick database access with data munging on either side, cluster access, etc. it works fine for basic shell usage though. As for a more complex example: yes, the website has better examples, but they are also more involved to explain.
- geophile 3y agoAlmost forgot: I also switch from bash to Python at a low threshold. In that case, I find Marcel’s API useful. I can then do shell-like piping inside of Python.
- Too 3y agoUsing the output of find into another program is not safe due to risk of file names containing delimiters. You need to use find -exec. Good example of why machine readable output is important. Agree that the tutorial should showcase more and larger such examples.
- rmwaite 3y agoYou can always use -print0. I suppose there is some risk of a null slipping into a filename but I’ve never come across it myself.
- gnosek 3y ago> some risk of a null slipping into a filename Only in some fairly esoteric environments: https://en.wikipedia.org/wiki/Filename#Comparison_of_filename_limitations https://en.wikipedia.org/wiki/Filename#Comparison_of_filenam...
- js2 3y agoYes, I know that, but it's also exceedingly rare for a filename to contain a newline and using -exec is extremely inefficient. I also wrote that on my iPad. Typically I'd use a combination of -print0 and xargs -0 for anything more formal than a one-liner on the command line. The larger bug in my example is that it fails if any of the directories in the path contain a "." in their name!
- prometheon1 3y agoIn that case, is it even more similar to xonsh? https://xon.sh/ https://xon.sh/
- deleted 3y ago[deleted]
- geophile 3y agoI posted a comparison to xonsh elsewhere in this discussion.
- lars512 3y agoMarcel looks really interesting. As someone who's leaned into Nushell deeply, I can tell you that the tabular and hierarchical data output is the major selling point of Nushell. For me and my team, who work with data and metadata constantly, it's an incredible productivity boost. The major pains with Nushell are debugging pipelines that are too slow, having to learn the new language constructs, and process overhead for going in and out of Python for other pieces.
- geophile 3y agoIf you stick to marcel commands and python functions, then all the processing happens in a single Python process (with a small number of exceptions). Beside the process overhead, this approach also avoids serialization/deserialization costs, and even string copying costs. x | y | z just passes Python tuples from one command to another via function call. Can you expand on your first point? Why are tabular and hierarchical output so important for your work?