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Full Discussion: read file backwards
Top Forums Shell Programming and Scripting read file backwards Post 302137957 by bluemoon1 on Thursday 27th of September 2007 11:33:47 PM
Old 09-28-2007
read file backwards

Assume file1 contains a list of strings.
My first script is scanning the file and deals with the lines with a certain patern in it:

grep 'somepatern' file1 \
while read LINE ; do
doSomethingAboutIt
done

Now, I need a second script that deals with the same lines (& do something differently) but in the opposite order; the last line found in the file with that patern shuld be handled first.

Please help me. Thanks so much!!!

Last edited by bluemoon1; 09-28-2007 at 12:36 AM.. Reason: typo
 

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paste(1)						      General Commands Manual							  paste(1)

Name
       paste - merge file data

Syntax
       paste file1 file2...
       paste -dlist file1 file2...
       paste -s [-dlist] file1 file2...

Description
       In  the	first  two forms, concatenates corresponding lines of the given input files file1, file2, etc.	It treats each file as a column or
       columns of a table and pastes them together horizontally (parallel merging).

       In the last form, the command combines subsequent lines of the input file (serial merging).

       In all cases, lines are glued together with the tab character, or with characters from an optionally specified  list.   Output  is  to  the
       standard output, so it can be used as the start of a pipe, or as a filter, if - is used in place of a file name.

Options
       -       Used in place of any file name, to read a line from the standard input.	(There is no prompting).

       -dlist  Replaces  characters  of  all but last file with nontabs characters (default tab).  One or more characters immediately following -d
	       replace the default tab as the line concatenation character.  The list is used circularly, i. e. when exhausted, it is reused.	In
	       parallel  merging  (i. e. no -s option), the lines from the last file are always terminated with a new-line character, not from the
	       list.  The list may contain the special escape sequences: 
 (new-line), 	 (tab), \ (backslash), and  (empty string, not a null
	       character).   Quoting  may  be  necessary,  if characters have special meaning to the shell (for example, to get one backslash, use
	       -d"\\" ).
	       Without this option, the new-line characters of each but the last file (or last line in case of the -s option) are  replaced  by  a
	       tab character.  This option allows replacing the tab character by one or more alternate characters (see below).

       -s      Merges  subsequent  lines  rather  than	one  from  each input file.  Use tab for concatenation, unless a list is specified with -d
	       option.	Regardless of the list, the very last character of the file is forced to be a new-line.

Examples
       ls | paste -d" " -
       list directory in one column
       ls | paste - - - -
       list directory in four columns
       paste -s -d"	
" file
       combine pairs of lines into lines

Diagnostics
       line too long
		 Output lines are restricted to 511 characters.

       too many files
		 Except for -s option, no more than 12 input files may be specified.

See Also
       cut(1), grep(1), pr(1)

																	  paste(1)
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