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Full Discussion: Merge multiple lines in same file with common key using awk
Top Forums Shell Programming and Scripting Merge multiple lines in same file with common key using awk Post 302735721 by elixir_sinari on Monday 26th of November 2012 04:10:15 AM
Old 11-26-2012
Quote:
Where does p1 come from?
p1 is used to store the value of the first field. Since this is done at the end of each line processing, it becomes the previous value of the first field for the current line.

Quote:
Is prev a built-in variable?
No. In awk, the built-in variables are all upper-case words. prev is used to store the line made up by appending segments of the lines which have common first fields. After printing each made-up line, we need to nullify the variable to make it ready for the next line to be made up.

And the cryptic line does what you thought it does. If prev"" (prev is not-null) is true, then we must be having at least 1 line in prev so we need to append a , (FS - field separator, comma in this case, and that's a special/built-in awk variable) and the substring of the line from the second field onwards. Else if prev is null, then it must be the first time since printing the last prev. So, just assign the current line ($0) to prev.

And, I think you've understood rest of the things.
 

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prev

prev(1mh)																 prev(1mh)

Name
       prev - show the previous message

Syntax
       prev [ +folder ] [ -[no]header ] [ -help ] [ -showproc program ] [ -noshowproc ] [ options to ]

Description
       The command displays the previous message in the current folder.  The previous message is the one before the current message in the folder.
       The message that is shown becomes the current message.

       You can specify a folder other than the current folder by using the +folder argument.  If you specify a folder, that  becomes  the  current
       folder.

Options
       -header
       -noheader Displays  a  one-line	header before the message.  The header consists of the name of the folder and the message number.  This is
		 the default behavior.	It can be suppressed with the -noheader option.

       -help	 Prints a list of the valid options to this command.

       -showproc program [ options ]
       -noshowproc
		 Specifies an alternative program to list messages.  The default is to use the program defined by the showproc: entry in the file.
		 As with you can give options to the program at the command line.  These are passed directly to by

       The defaults for this command are:

	      +folder defaults to the current folder
	      -header

Restrictions
       The  command  is  really  a  link  to  the program.  As a result, if you make a link to and that link is not called your link will act like
       instead.  To avoid this, add a profile-entry for the link to your MH profile and add the argument to the entry.

Examples
       The command in the following example displays the previous message in the folder
       $ prev +copylog

Profile Components
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Files
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See Also
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