is it possible to get the display used by xrdp-sesrun

[gnzsnz]

I'm running a docker container with xfc (linuxserver rdesktop image). and I have created a script that will open a session using xrdp-sesrun once the session is open i need to lauch an application, which works well if the DISPLAY is set correctly.

usually i set DISPLAY=10 and works, but on the latest update of the image sometimes it's using 11 or 12. so i can not pre-define it.

is it possible to capture which one is using?

thanks in advance for your help and great software

root@04340439949c:/# xrdp -v
xrdp 0.9.17
  A Remote Desktop Protocol Server.
  Copyright (C) 2004-2020 Jay Sorg, Neutrino Labs, and all contributors.
  See https://github.com/neutrinolabs/xrdp for more information.

  Configure options:
      --enable-ipv6
      --enable-jpeg
      --enable-fuse
      --enable-rfxcodec
      --enable-opus
      --enable-painter
      --enable-vsock
      --build=x86_64-linux-gnu
      --prefix=/usr
      --includedir=${prefix}/include
      --mandir=${prefix}/share/man
      --infodir=${prefix}/share/info
      --sysconfdir=/etc
      --localstatedir=/var
      --disable-silent-rules
      --libdir=${prefix}/lib/x86_64-linux-gnu
      --libexecdir=${prefix}/lib/x86_64-linux-gnu
      --disable-maintainer-mode
      --disable-dependency-tracking
      --with-socketdir=/run/xrdp/sockdir
      build_alias=x86_64-linux-gnu
      CFLAGS=-g -O2 -ffile-prefix-map=/build/xrdp-asBei3/xrdp-0.9.17=. -flto=auto -ffat-lto-objects -flto=auto -ffat-lto-objects -fstack-protector-strong -Wformat -Werror=format-security
      LDFLAGS=-Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -flto=auto -Wl,-z,relro -Wl,-z,now -Wl,--as-needed
      CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=2 -Wno-error=deprecated-declarations
      PKG_CONFIG_PATH=/build/xrdp-asBei3/xrdp-0.9.17/pkgconfig

  Compiled with OpenSSL 3.0.2 15 Mar 2022

[gnzsnz]

on #1898 (comment) @matt335672 implied that might be possible (?)

[matt335672]

I think xrdp-sesrun for that version of xrdp tells you what display it's used. Can you pick that up?

[gnzsnz]

thanks for pointing me on the right direction @matt335672

if i do

echo "$(</run/secrets/password)" | xrdp-sesrun -F0 -s 127.0.0.1 testuser
[20240423-10:19:47] [WARN ] Using deprecated option '-s'
ok data=1 display=:10 GUID=98063e9769df1308631010e85f794230

I get the display in the otput, among warnings and other information

this is giving me the display

echo "$(</run/secrets/password)" | xrdp-sesrun -F0 -s 127.0.0.1 testuser| grep -e '^ok' | cut -d ' ' -f 3 | cut -d '=' -f 2
:10

if there is a better way please let me know. thanks in advance for your help

[matt335672]

You can use sed to cut down the number of processes you're using, but this is (IMO) a bit less readable. It's also quite fiddly to get the backslashes right:-

$ echo 'ok data=1 display=:10 GUID=98063e9769df1308631010e85f794230' | \
    sed -ne 's/^ok.*display=\(:[0-9]*\).*/\1/p'
:10

A breakdown:-

feature	Explanation
sed -ne	Parse stdin with the following expression. Don't echo by default
\(:[0-9]*\)	Match a colon followed by 0 or more digits, and place in variable \1
^ok.*display=\(:[0-9]*\).*	Match a complete line starting with ok, with display=:[0-9]* in it. Store :[0-9]* in variable \1
s/<regular-expression>/\1/p	Substitute the entire matched regular expression with \1 and print the result if matched

[gnzsnz]

This is fantastic @matt335672 thanks so much for your help.