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Re: Feature request or advice on implementation for buffering command ou


From: Greg Wooledge
Subject: Re: Feature request or advice on implementation for buffering command output
Date: Mon, 8 Apr 2019 08:41:43 -0400
User-agent: Mutt/1.10.1 (2018-07-13)

On Fri, Apr 05, 2019 at 03:57:16PM -0700, L A Walsh wrote:
>     What would be wrong with doing something like:
> 
> readarray -t last10< <(COMMAND |tail -10)
> 
> That will put the last 10 lines of COMMAND_OUTPUT into
> the array 'last10'.  Now you can launch another command
> to process that last 10 lines.  Note that I used the '-t'
> which strips off the '\n' at the end of line.  For about
> 50% of the uses, you might want to keep the line ending
> (and not use the '-t' option).  Example.  Using 'seq'
> to generate lines of output, if I use -t, I might get:
> 
> > readarray -t last10< <(seq 1 100|tail -10)
> > printf "%s" "address@hidden"
> 919293949596979899100>
> 
> Which may not be what you want.  But you could keep the
> newline when reading it in and it will be used on output:
> 
> > readarray last10< <(seq 1 100|tail -10)
> > printf "%s" "address@hidden"
> 91
> 92
> 93
> 94
> 95
> 96
> 97
> 98
> 99
> 100

That would be an extremely uncomfortable way to use an array of numbers
for any purpose other than printing them to stdout.

You virtually always want to use readarray -t, to store the numbers
without their trailing newlines.  That lets you use them as numbers in
math contexts, or print them as part of a line of text, etc.  If you
want to print them one-per-line, you can simply do:

printf '%s\n' "address@hidden"



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