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Full Discussion: reversing a list
Top Forums Shell Programming and Scripting reversing a list Post 29829 by TioTony on Friday 11th of October 2002 05:42:38 PM
Old 10-11-2002
reversing a list

Hi Everyone,
I am reading in a list of IDs from a file that is is chronological order. My current code in simplified form looks like this (ksh by the way)

IDS=`awk -F\| '{print $1}' inputfile.txt`
for i in $IDS
do
do various things with that ID
done

inputfile.txt looks like this:

1|stuff|more stuff|etc
2|stuff|more stuff|etc
3|stuff|more stuff|etc
.
.
.
10000|stuff|more stuff|etc

What I would like to do is start with the last ID (10000) and work towards the first ID (1). This is an oversimplified example. There are gaps between IDs, the may not be consecutive. I cannot do a while loop starting with i=10000 and decrement to 1 due to this. Any ideas how I could reverse the values in $IDS before the for loop? The input file can be manipulated prior to calling the script. I thought there was a command to invert a list but I can't remember what it is and can't find it ( I searched the forum + google + man -k)
Thanks,
Tony
 

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GIT-STRIPSPACE(1)                                                   Git Manual                                                   GIT-STRIPSPACE(1)

NAME
git-stripspace - Remove unnecessary whitespace SYNOPSIS
git stripspace [-s | --strip-comments] git stripspace [-c | --comment-lines] DESCRIPTION
Read text, such as commit messages, notes, tags and branch descriptions, from the standard input and clean it in the manner used by Git. With no arguments, this will: o remove trailing whitespace from all lines o collapse multiple consecutive empty lines into one empty line o remove empty lines from the beginning and end of the input o add a missing to the last line if necessary. In the case where the input consists entirely of whitespace characters, no output will be produced. NOTE: This is intended for cleaning metadata, prefer the --whitespace=fix mode of git-apply(1) for correcting whitespace of patches or files in the repository. OPTIONS
-s, --strip-comments Skip and remove all lines starting with comment character (default #). -c, --comment-lines Prepend comment character and blank to each line. Lines will automatically be terminated with a newline. On empty lines, only the comment character will be prepended. EXAMPLES
Given the following noisy input with $ indicating the end of a line: |A brief introduction $ | $ |$ |A new paragraph$ |# with a commented-out line $ |explaining lots of stuff.$ |$ |# An old paragraph, also commented-out. $ | $ |The end.$ | $ Use git stripspace with no arguments to obtain: |A brief introduction$ |$ |A new paragraph$ |# with a commented-out line$ |explaining lots of stuff.$ |$ |# An old paragraph, also commented-out.$ |$ |The end.$ Use git stripspace --strip-comments to obtain: |A brief introduction$ |$ |A new paragraph$ |explaining lots of stuff.$ |$ |The end.$ GIT
Part of the git(1) suite Git 2.17.1 10/05/2018 GIT-STRIPSPACE(1)
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