3 ms·

One more fun experiment: avoid the tempfile on disk/tmpfs by storing data into the pipe connecting two processes, where the first one can already exit for the p

One more fun experiment: avoid the tempfile on disk/tmpfs by storing data into the pipe connecting two processes, where the first one can already exit for the pipe to give EOF when reading beyond the buffered data. true | sleep infinity & STDINPID="$!" TMPPIPE="/proc/$STDINPID/fd/0" echo hello > "$TMPPIPE" echo write more > "$TMPPIPE" cat "$TMPPIPE" echo write again > "$TMPPIPE" cat "$TMPPIPE" kill -9 "$STDINPID" # clean up pipe Now I would like to avoid the additional process by using the current shell process instead.

goombacloud 5y ago
Still needs to spawn a temporary process but it can be killed early: true | sleep infinity & STDINPID="$!" exec {mypipe}<"/proc/$STDINPID/fd/0" # hijack FD TMPPIPE="/proc/$$/fd/${mypipe}" disown "$STDINPID" # suppress killed message on stderr kill -9 "$STDINPID" # clean up process now already echo hello > "$TMPPIPE" echo write more > "$TMPPIPE" cat "$TMPPIPE" echo write again > "$TMPPIPE" cat "$TMPPIPE"
- Klasiaster 5y ago
  Seems "sleep 60" is safer and still good enough unless the system is completely overloaded.
- dzove855 5y ago
  Since now, multiple concurrent connections will work after my patch. (Need to add subshell) i will need to consider using fd as output cache. Instead of temporary files.
  - Klasiaster 5y ago
    This here is a simple echo server that uses tr to uppercase: exec {checkfd}>/dev/null CHECKFDPATH="/proc/$$/fd/${checkfd}" (while [ -e "$CHECKFDPATH" ]; do sleep 1; done) > >(true) & STDINPID="$!" WRITER="/proc/$STDINPID/fd/1" while IFS= read -r LINE; do # only echo lines if we didn't close the connection yet if [ -e "$CHECKFDPATH" ]; then echo "$LINE" | tr '[:lower:]' '[:upper:]' > "$WRITER" if [ "$LINE" = "bye" ]; then exec {checkfd}<&- fi else echo "received while closed: $LINE" fi done < <(nc -q 1 -l 8080 < "$WRITER") if [ -e "$CHECKFDPATH" ]; then # close checkfd to close writer pipe exec {checkfd}<&- fi
    - Klasiaster 5y ago
      This variant here works a bit different: exec {checkfd}>/dev/null CHECKFDPATH="/proc/$$/fd/${checkfd}" (while [ -e "$CHECKFDPATH" ]; do sleep 1; done) > >(true) & STDINPID="$!" disown "$STDINPID" READER="/proc/$STDINPID/fd/1" { while IFS= read -r LINE; do echo "$LINE" | tr '[:lower:]' '[:upper:]' if [ "$LINE" = "bye" ]; then echo exiting > /dev/stderr break fi done < "$READER" ; kill -9 "$STDINPID" 2>/dev/null || true ; } | { nc -q 1 -l 8080 > "$READER" ; kill -9 "$STDINPID" 2>/dev/null || true ; } exec {checkfd}<&-
  - dzove855 5y ago
    No need of tr here in your example. The fd will only be used to stor it temporary since, we first need to sent headers, and the headers need to be sent before the bofy. The server base os working fine now with accept and a patch request os already sent to bash. So probaböy on the next release accept will be full usable.

goombacloud 5y ago

Still needs to spawn a temporary process but it can be killed early: true | sleep infinity & STDINPID="$!" exec {mypipe}<"/proc/$STDINPID/fd/0" # hijack FD TMPPIPE="/proc/$$/fd/${mypipe}" disown "$STDINPID" # suppress killed message on stderr kill -9 "$STDINPID" # clean up process now already echo hello > "$TMPPIPE" echo write more > "$TMPPIPE" cat "$TMPPIPE" echo write again > "$TMPPIPE" cat "$TMPPIPE"

Klasiaster 5y ago
Seems "sleep 60" is safer and still good enough unless the system is completely overloaded.
dzove855 5y ago
Since now, multiple concurrent connections will work after my patch. (Need to add subshell) i will need to consider using fd as output cache. Instead of temporary files.
- Klasiaster 5y ago
  This here is a simple echo server that uses tr to uppercase: exec {checkfd}>/dev/null CHECKFDPATH="/proc/$$/fd/${checkfd}" (while [ -e "$CHECKFDPATH" ]; do sleep 1; done) > >(true) & STDINPID="$!" WRITER="/proc/$STDINPID/fd/1" while IFS= read -r LINE; do # only echo lines if we didn't close the connection yet if [ -e "$CHECKFDPATH" ]; then echo "$LINE" | tr '[:lower:]' '[:upper:]' > "$WRITER" if [ "$LINE" = "bye" ]; then exec {checkfd}<&- fi else echo "received while closed: $LINE" fi done < <(nc -q 1 -l 8080 < "$WRITER") if [ -e "$CHECKFDPATH" ]; then # close checkfd to close writer pipe exec {checkfd}<&- fi
  - Klasiaster 5y ago
    This variant here works a bit different: exec {checkfd}>/dev/null CHECKFDPATH="/proc/$$/fd/${checkfd}" (while [ -e "$CHECKFDPATH" ]; do sleep 1; done) > >(true) & STDINPID="$!" disown "$STDINPID" READER="/proc/$STDINPID/fd/1" { while IFS= read -r LINE; do echo "$LINE" | tr '[:lower:]' '[:upper:]' if [ "$LINE" = "bye" ]; then echo exiting > /dev/stderr break fi done < "$READER" ; kill -9 "$STDINPID" 2>/dev/null || true ; } | { nc -q 1 -l 8080 > "$READER" ; kill -9 "$STDINPID" 2>/dev/null || true ; } exec {checkfd}<&-
- dzove855 5y ago
  No need of tr here in your example. The fd will only be used to stor it temporary since, we first need to sent headers, and the headers need to be sent before the bofy. The server base os working fine now with accept and a patch request os already sent to bash. So probaböy on the next release accept will be full usable.