Hi! To quote https://www.gnu.org/software/bash/manual/html_node/Coprocesses.html#Coprocesses
"The file descriptors are not available in subshells." So, that is my expectation. However, the following Bash fails me: Configuration Information [Automatically generated, do not change]: Machine: x86_64 OS: linux-gnu Compiler: gcc Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-unknown-linux-gnu' -DCONF_VENDOR='unknown' -DLOCALEDIR='/usr/local/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H -I. -I. -I./include -I./lib -g -O2 -Wno-parentheses -Wno-format-security uname output: Linux 0x657573 4.4.0-111-generic #134-Ubuntu SMP Mon Jan 15 14:53:09 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux Machine Type: x86_64-unknown-linux-gnu Bash Version: 4.4 Patch Level: 12 Release Status: release Description: First, to quote https://www.gnu.org/software/bash/manual/html_node/Command-Substitution.html#Command-Substitution "Bash performs the expansion by executing command in a subshell environment" However, the following works: coproc cat >/tmp/test.txt; echo x $(echo hello777 >&${COPROC[1]}) y; exec {COPROC[1]}<&- ; cat /tmp/test.txt Specifically, I use command substitution to feed the coproc with hello777. And, the coproc receives that string storing it in /tmp/test.txt. But, command substitution creates a subshell. So, coproc file descriptors are available in subshells, contradicting coproc documentation. Second, to quote https://www.gnu.org/software/bash/manual/html_node/Process-Substitution.html#Process-Substitution "The process list is run asynchronously" However, the following works: coproc cat >/tmp/test.txt; cat <(echo hello888 >&${COPROC[1]}); exec {COPROC[1]}<&- ; cat /tmp/test.txt Specifically, I use process substitution to feed the coproc with hello888. And, the coproc receives that string storing it in /tmp/test.txt. But, process substitution creates a subshell because it runs asynchronously. So, coproc file descriptors are available in subshells, contradicting coproc documentation. How should the contradiction be resolved? Thank you. -- Best regards, Tadeus
