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Full Discussion: UNIX Scripting
Top Forums Shell Programming and Scripting UNIX Scripting Post 302886950 by Don Cragun on Tuesday 4th of February 2014 02:33:02 PM
Old 02-04-2014
Quote:
Originally Posted by ocrambo
Hi Vinoth, great.

for those calling things useless...... In my opinion using `cat` as an example is easy to understand, so useful. There are many one-liners (without useless things) which take hours to understand what is really happening. My scripts are easy to read, how 'bout yours??????
Using:
Code:
cat file | grep expression

  • uses two processes,
  • causes the data in file to be read by cat, written by cat, and read again by grep, and
  • runs slower
than using:
Code:
grep expression file
    or
grep expression < file

both of which:
  1. use only one process,
  2. only reads the data in file once, and
  3. run faster.
That is why we call the first form a useless (and inefficient) use of cat.
With a little more experience, you will find either of the latter forms of these command lines just as easy to read as the first form.
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