---
syntax: markdown
tags: [tldr, common]
source: https://github.com/tldr-pages/tldr.git
---
# 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 <&"${{{name[0]}}}" {{variable}}`

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