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From: mcgrew@ichthous.Eng.Sun.COM (Darin McGrew)
Newsgroups: comp.unix.shell
Subject: Re: Problem using multiple 'head' commands in shell script
Keywords: head shell buffering
Message-ID: <6925@exodus.Eng.Sun.COM>
Date: 30 Jan 91 01:52:08 GMT
References: <1671@abekrd.UUCP>
Sender: news@exodus.Eng.Sun.COM
Organization: Sun Microsystems, Mt. View, Ca.
Lines: 34

In article <1671@abekrd.UUCP> garyb@abekrd.UUCP (Gary Bartlett) writes:
->Can someone explain to me what is happening with the following Bourne shell
->script and more importantly how I can get around it:
->
->	#!/bin/sh
->	cat file | (
->		head -200
->		echo "Line 201 follows"
->		head -200
->		echo "Line 401 follows"
->		cat
->	)
->
->...
->It looks like 'head' initially reads in a whole buffer of data from file
->(stdin), prints out the requisite number of lines and then dumps the rest
->of the buffer.  The next 'head' then reads the NEXT buffer....

Yes, head reads a bufferful at a time.  I'd use awk:

	awk '	NR==201	{print "Line 201 follows"}
		NR==401	{print "Line 401 follows"}
			{print}' < file

->Thanks,
->Gary

You're welcome.

                 Darin McGrew     "The Beginning will make all things new,
           mcgrew@Eng.Sun.COM      New life belongs to Him.
       Affiliation stated for      He hands us each new moment saying,
identification purposes only.      'My child, begin again....
				    You're free to start again.'"