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Full Discussion: Removing all lines prior to the last pattern in a file/stream
Top Forums Shell Programming and Scripting Removing all lines prior to the last pattern in a file/stream Post 302503758 by LivinFree on Friday 11th of March 2011 01:50:02 PM
Old 03-11-2011
Removing all lines prior to the last pattern in a file/stream
Hi all,

I didn't find anything that specifically answers this after searching for a bit, so please forgive me if this has been covered before.

I'm looking to delete all lines prior to the last occurrence of a string in a file or stream from within a shell script (bash.)

A bit of background:
I'm running a command to pull the contents of a circular buffer, so I get whatever happens to be there. I'm only interested in the last string and the contents after that for each command I run. If can operate on the stream as it comes out and before it's written to a file, that'd be ideal. I'd also like to use sed if possible, since I use it in other areas of the script and I want to keep in all in-line.

An pseudo-example of the output I might get is below:
Code:
# run_async_command "mark command start test"
# pull_serial_log
^@CLI> [20372:53.558][20372:59.504] command^@ start^@ test^@
command output 1
command output 1
[...]
command output 1
^@CLI> [20372:53.558][20372:59.504] command^@ some^@ other^@ test^@
command output 2
command output 2
[...]
command output 2
^@CLI> [20372:53.558][20372:59.504] command^@ start^@ test^@
command output 3
command output 3
[...]
command output 3
#

In this case, all I'd want to see is the last instance of "command^@start^@ test^@" followed by its output to the end of the stream/file. Note that the "^@" characters here represent NULL characters. The command output is an arbitrary number of lines - it may be 10 lines, or it may be 1000 lines, and has no specific structure. Here's what I would like to see:
Code:
# run_async_command "mark command start test"
# pull_serial_log | sed -n 'MAGIC_GOES_HERE'
^@CLI> [20372:53.558][20372:59.504] command^@ start^@ test^@
command output 3
command output 3
[...]
command output 3
#

What I plan on doing is running the run_async_command, then dumping the buffer and stripping out only the last command, then run_async_command again with a different command and stripping out only the output from that command, and so on.

Please let me know if anyone wants more details.
 

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xtmenupopup

XtMenuPopup()															     XtMenuPopup()

Name
  XtMenuPopup - built-in action for popping up a widget.

Synopsis (Translation Table)
  <Event sequence>: XtMenuPopup(shell_name)

Inputs
  shell_name
	    Specifies the name of the widget shell to pop up.

Availability
  This action is named MenuPopup prior to Release 4.

Description
  XtMenuPopdown  is a predefined action procedure which does not have a corresponding public C routine.  It can only be invoked from a trans-
  lation table.

  XtMenuPopup tries to find the named shell by searching the widget tree starting at the widget in which it is invoked.  If it finds a	shell
  with the specified name in the popup children of that widget, it pops up the shell with the appropriate parameters.  Otherwise, it moves up
  the parent chain to find a popup child with the specified name.  If XtMenuPopup gets to the application top-level shell widget and has  not
  found a matching shell, it generates a warning and returns immediately.

  If  XtMenuPopup is invoked on ButtonPress, it calls XtPopupSpringLoaded() on the specified shell widget.  If XtMenuPopup is invoked on Key-
  Press or EnterWindow, it calls XtPopup() on the specified shell widget with grab_kind set to XtGrabNonexclusive.  Otherwise,	the  transla-
  tion manager generates a warning message and ignores the action.

  XtMenuPopup  is specially registered with the translation manager as an action that will invoke a grab.  This registration is done by call-
  ing XtRegisterGrabAction() specifying owner_events True, event_mask ButtonPressMask	ButtonReleaseMask, and pointer_mode and keyboard_mode
  GrabModeAsync.

Usage
  Note that XtMenuPopup is an action procedure; you cannot call it from C code.

  MenuPopup is a synonym for XtMenuPopup.

  Popup  shells  can  also  be popped up explicitly using XtPopup(), XtPopupSpringLoaded() or one of the predefined popup callback procedures
  (see XtCallbackExclusive()).

  The action XtMenuPopdown can be used to pop down a shell widget from a translation table.

See Also
  XtMenuPopdown(1), XtPopDown(1), XtPopup(1), XtPopupSpringLoaded(1), XtRegisterGrabAction(1).

Xt - Pop Ups															     XtMenuPopup()
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