tldr/pages/linux/coproc.md

# coproc

> Bash builtin for creating interactive asynchronous subshells.
> More information: <https://www.gnu.org/software/bash/manual/bash.html#Coprocesses>.

- Run a subshell asynchronously:

`coproc { {{command1; command2; ...}}; }`

- Create a coprocess with a specific name:

`coproc {{name}} { {{command1; command2; ...}}; }`

- Write to a specific coprocess `stdin`:

`echo "{{input}}" >&"${{{name}}[1]}"`

- Read from a specific coprocess `stdout`:

`read {{variable}} <&"${{{name}}[0]}"`

- Create a coprocess which repeatedly reads `stdin` and runs some commands on the input:

`coproc {{name}} { while read line; do {{command1; command2; ...}}; done }`

- Create a coprocess which repeatedly reads `stdin`, runs a pipeline on the input, and writes the output to `stdout`:

`coproc {{name}} { while read line; do echo "$line" | {{command1 | command2 | ...}} | cat /dev/fd/0; done }`

- Create and use a coprocess running `bc`:

`coproc BC { bc --mathlib; }; echo "1/3" >&"${BC[1]}"; read output <&"${BC[0]}"; echo "$output"`