How to display the current process tree of a bash session?

Question

I would like to create a bash alias that gives me the process tree from the current bash session I am using, up to init.

The use case is to know whether I have used bash or vi's :shell command.

I am using MacOS X. I have heard about pstree, but it seems to only show children, not the relationship between init and the current process.

Answer 1

I am sure with a a bit of google search, you can find how to get and download pstree for the Mac. However, you can do a poor man's version, using ps and ppid.

eg

ps -eo ppid,pid,cmd | awk '{p[$1]=p[$1]","$3}END{ for(i in p) print i, p[i]}'

Answer 2

This is supported in pstree(1) by using an option to show the tree only for a particular PID and providing the current process's PID ($$ in Bash), The option is named differently between GPL-licensed version by Werner Almesberger distributed with Debian and the BSD version by Fred Hucht distributed with MacOS.

• On Debian/Ubuntu: pstree -s $$

  init───gnome-terminal───bash───pstree
  

  Summary of -s option:

  -s     Show parent processes of the specified process.
  

• On MacOS: pstree -p $$

  -+= 00001 root /sbin/launchd
   \-+= 25706philipbranning/Applications/Utilities/Terminal.app/Contents/MacOS/Terminal
     \-+= 25716 root login -pfl philipbranning /bin/bash -c exec -la bash /bin/bash
       \-+= 25722 philipbranning -bash
         \-+= 32456 philipbranning pstree -p 25722
           \--- 32457 root ps -axwwo user,pid,ppid,pgid,command
  

  Summary of -p option:

  -p pid    show only branches containing process <pid>
  

Here's your alias for MacOS:

alias psme='pstree -p $$'