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[GH-ISSUE #255] Output recording to stdout #796

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opened 2026-03-15 10:30:06 +03:00 by kerem · 10 comments

kerem commented

2026-03-15 10:30:06 +03:00

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Originally created by @sindresorhus on GitHub (Dec 29, 2017).
Original GitHub issue: https://github.com/asciinema/asciinema/issues/255

Would be useful if asciinema had a flag to output the recording to stdout. This would make it easy to use the recording with other tools without having to write and then read a temp file.

This is what I currently have to do:

temp_file=$(mktemp); asciinema rec $temp_file --command="node example.js" --quiet; cat $temp_file | svg-term --out=screenshot.svg

This is how I'd like to use it:

asciinema rec --command="node example.js" --stdout --quiet | svg-term --out=screenshot.svg

Or just output to stdout if no filename is given.

This is the tool I'm using with asciinema: https://github.com/marionebl/svg-term-cli

// @marionebl

Originally created by @sindresorhus on GitHub (Dec 29, 2017). Original GitHub issue: https://github.com/asciinema/asciinema/issues/255 Would be useful if `asciinema` had a flag to output the recording to stdout. This would make it easy to use the recording with other tools without having to write and then read a temp file. This is what I currently have to do: ``` temp_file=$(mktemp); asciinema rec $temp_file --command="node example.js" --quiet; cat $temp_file | svg-term --out=screenshot.svg ``` This is how I'd like to use it: ``` asciinema rec --command="node example.js" --stdout --quiet | svg-term --out=screenshot.svg ``` Or just output to stdout if no filename is given. This is the tool I'm using with `asciinema`: https://github.com/marionebl/svg-term-cli // @marionebl

kerem closed this issue

2026-03-15 10:30:11 +03:00

kerem commented

2026-03-15 10:30:17 +03:00

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@ku1ik commented on GitHub (Apr 5, 2018):

If you redirected asciinema rec's stdout to a pipe then you wouldn't see what you're doing in your terminal ;) The stdout has to go directly to terminal emulator, without any redirects/captures. In other words it's impossible to achieve it with pipe.

But you can try this (works in bash, and probably in zsh too):

asciinema rec -c "node example.js" >(svg-term --out=screenshot.svg)

>(some command) runs some command in a subshell, creates a file (pipe) at /dev/fd/... which is connected to this command's stdin, and then the whole >(...) expression is replaced with /dev/fd/... path :)

I did it with wc -l, which counted lines of the resulting recording, printing 27:

bash-3.2$ asciinema rec >(wc -l)
asciinema: recording asciicast to /dev/fd/63
asciinema: press <ctrl-d> or type "exit" when you're done
bash-3.2$
...
...
bash-3.2$ exit
asciinema: recording finished
asciinema: asciicast saved to /dev/fd/63
      27

@ku1ik commented on GitHub (Apr 5, 2018): ~~If you redirected `asciinema rec`'s stdout to a pipe then you wouldn't see what you're doing in your terminal ;) The stdout has to go directly to terminal emulator, without any redirects/captures. In other words it's impossible to achieve it with pipe.~~ But you can try this (works in bash, and probably in zsh too): asciinema rec -c "node example.js" >(svg-term --out=screenshot.svg) `>(some command)` runs `some command` in a subshell, creates a file (pipe) at `/dev/fd/...` which is connected to this command's stdin, and then the whole `>(...)` expression is replaced with `/dev/fd/...` path :) I did it with `wc -l`, which counted lines of the resulting recording, printing `27`: ``` bash-3.2$ asciinema rec >(wc -l) asciinema: recording asciicast to /dev/fd/63 asciinema: press <ctrl-d> or type "exit" when you're done bash-3.2$ ... ... bash-3.2$ exit asciinema: recording finished asciinema: asciicast saved to /dev/fd/63 27 ```

kerem commented

2026-03-15 10:30:22 +03:00

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@chewi commented on GitHub (Dec 19, 2018):

I tried the >() approach but it doesn't work now. It complains of an illegal seek.

@chewi commented on GitHub (Dec 19, 2018): I tried the `>()` approach but it doesn't work now. It complains of an illegal seek.

kerem commented

2026-03-15 10:30:27 +03:00

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@ku1ik commented on GitHub (Dec 19, 2018):

That is an advanced bash trick, so it may not work in all cases.

@ku1ik commented on GitHub (Dec 19, 2018): That is an advanced bash trick, so it may not work in all cases.

kerem commented

2026-03-15 10:30:32 +03:00

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@glaudiston commented on GitHub (Dec 3, 2020):

Have you tried with echo and jq in bash ?:

echo -e "$(cat your-asciinema.json | jq '.stdout[][1]' | tr -d '"\n\r')"

@glaudiston commented on GitHub (Dec 3, 2020): Have you tried with `echo` and `jq` in bash ?: ``` echo -e "$(cat your-asciinema.json | jq '.stdout[][1]' | tr -d '"\n\r')" ```

kerem commented

2026-03-15 10:30:37 +03:00

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@ku1ik commented on GitHub (Feb 20, 2022):

The improvements from https://github.com/asciinema/asciinema/pull/473 make it possible to do this:

asciinema rec --command="node example.js" --quiet /dev/stdout | svg-term --out=screenshot.svg

This will be released in v2.2.

@ku1ik commented on GitHub (Feb 20, 2022): The improvements from https://github.com/asciinema/asciinema/pull/473 make it possible to do this: ```bash asciinema rec --command="node example.js" --quiet /dev/stdout | svg-term --out=screenshot.svg ``` This will be released in v2.2.

kerem commented

2026-03-15 10:30:42 +03:00

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@ku1ik commented on GitHub (Apr 28, 2022):

Also I just merged #492 which allows use of - as the filename representing stdout, then piping the output to another tool:

sciinema rec --command="node example.js" - | svg-term --out=screenshot.svg

@ku1ik commented on GitHub (Apr 28, 2022): Also I just merged #492 which allows use of `-` as the filename representing stdout, then piping the output to another tool: ``` sciinema rec --command="node example.js" - | svg-term --out=screenshot.svg ```

kerem commented

2026-03-15 10:30:47 +03:00

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@sashaaro commented on GitHub (May 12, 2022):

@sickill can you implement read terminal stdout steam via pipe without specify and run command

bash -c "./install.sh" | asciinema rec "install.cast"

actually I need it for use pipe programmly while write extension for https://github.com/vercel/hyper
idea in background run asciinema and forward stream to asciinema like

var child = require('child_process');
var asciinemaProc = child.spawn('asciinema rec ...');

hyperTerminalStream.stdout.pipe(asciinemaProc.stdin, { end: false });

@sashaaro commented on GitHub (May 12, 2022): @sickill can you implement read terminal stdout steam via pipe without specify and run command ```bash bash -c "./install.sh" | asciinema rec "install.cast" ``` actually I need it for use pipe programmly while write extension for https://github.com/vercel/hyper idea in background run asciinema and forward stream to asciinema like ```js var child = require('child_process'); var asciinemaProc = child.spawn('asciinema rec ...'); hyperTerminalStream.stdout.pipe(asciinemaProc.stdin, { end: false }); ```

kerem commented

2026-03-15 10:30:52 +03:00

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@ku1ik commented on GitHub (May 17, 2022):

@sashaaro You can do it the other way around:

asciinema rec -c ./install.sh install.cast

Or if you explicitly want bash to execute the script (in case the script doesn't have shebang line):

asciinema rec -c "bash -c ./install.sh" install.cast

@ku1ik commented on GitHub (May 17, 2022): @sashaaro You can do it the other way around: ```bash asciinema rec -c ./install.sh install.cast ``` Or if you explicitly want bash to execute the script (in case the script doesn't have shebang line): ```bash asciinema rec -c "bash -c ./install.sh" install.cast ```

kerem commented

2026-03-15 10:30:57 +03:00

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@ku1ik commented on GitHub (May 17, 2022):

Closing this as support to record to stdout (by specifying - as output filename) was added in 2.2.0.

@ku1ik commented on GitHub (May 17, 2022): Closing this as support to record to stdout (by specifying `-` as output filename) was added in 2.2.0.

kerem commented

2026-03-15 10:31:02 +03:00

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@sashaaro commented on GitHub (May 17, 2022):

@sickill unfortunately https://hyper.is/ plugins api does not allow to replace shell, hyper run shell command himself. I need run asciinema in backround separately and have method to send termianl stream to asciinema. Lets do asciinema just receive terminal stream via stdin pipe

@sashaaro commented on GitHub (May 17, 2022): @sickill unfortunately https://hyper.is/ plugins api does not allow to replace shell, hyper run shell command himself. I need run asciinema in backround separately and have method to send termianl stream to asciinema. Lets do asciinema just receive terminal stream via stdin pipe