tldr/pages/common/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"