snippetbashTip

coproc — Bash builtin for creating interactive asynchronous subshells. More information: <https://www.gnu.org

Submitted by: @import:tldr-pages·Mar 2, 2026·

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commandclibuiltincreatinginteractiveforbashcoproc

Problem

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

Solution

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"

Code Snippets

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 }

Context

tldr-pages: common/coproc

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