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Q&A

Continuously read from piped input using Vim

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In Vim, it's possible to tell it to read from stdin instead of a file, by using vim -. This is so that you can pipe the output of one command into Vim, to view/edit it there.

The problem I'm facing is that Vim seems to wait until the pipe is closed before starting up and displaying anything. It sits there saying Vim: Reading from stdin... until the piped command terminates. This can be a very long time, depending on the command!

Is there any way I can get Vim to instead start displaying immediately, and autoread as more data comes from the pipe?

My use case is trying to use Vim as a pager, so that I can have custom syntax highlighting and folding, for Git logs. My current attempts are failing because Vim waits until the entire log has been loaded before displaying anything at all.

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I don't think it's possible, but if it is, less.vim might do it (1 comment)

2 answers

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Unfortunately I think the simple answer is that you cannot do what you want with standard Vim (or NeoVim, which I also tested — although NeoVim is slightly more convenient in that you don't need to give the - argument to read from stdin).

Vim, like most text editors, is designed with the fundamental assumption that it is operating on a buffer of known size, rather than a stream of data which could be infinite in length. Once the input data is read, it is not read again unless you explicitly request another read operation with :e or similar. Although you can make Vim behave a bit like a pager using the - option, it is not really intended to be a replacement for less — it's more like a shortcut for process > /tmp/somefile.txt; vim /tmp/somefile.txt

Presumably in theory there's nothing to stop somebody from producing a modified version of Vim which has more pager-like features, although they'd need to consider how operations like "Go to the 50% position" would work in a potentially-infinite data stream (would this need to read the whole stream in order to find the true 50% mark, or just jump to 50% of the currently known data?)

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Maybe passing the piped results through tail first would partially work. Use tail with the -f flag so that tail will continuously its contents. Example: <cmd> | tail -f | vim -

I think you would still need to tell vim to get updates from tail periodically with :e!

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That won't work. `tail -f` is just another continuously outputting command; From Vim's perspective it... (1 comment)

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