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Full Discussion: Imitate head and tail command script
Top Forums Shell Programming and Scripting Imitate head and tail command script Post 302364780 by Scott on Friday 23rd of October 2009 09:10:36 PM
Old 10-23-2009
Sounds like a homework thing?

Anyway.

Interactive = read
Cat
wc for finding out how many lines there are
A handful of other commands
Awk for everything else

Code:
FILE=$1

echo "How many lines?: "
read HowMany

echo "Heads or tails? "
read HoT
case "$HoT" in
  h) awk 'NR <= '$HowMany $FILE ;;
  t) awk 'NR > '$(($(wc -l < $FILE) - $HowMany)) $FILE
esac

(there's a distinct lack of error checking here! $1 is the filename when calling this as a script from the command line)
Last edited by Scott; 10-23-2009 at 10:16 PM.. Reason: wc < file => wc < $FILE
 

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LEARN ABOUT LINUX

shuf

SHUF(1) 							   User Commands							   SHUF(1)

NAME

       shuf - generate random permutations

SYNOPSIS

       shuf [OPTION]... [FILE]
       shuf -e [OPTION]... [ARG]...
       shuf -i LO-HI [OPTION]...

DESCRIPTION

       Write a random permutation of the input lines to standard output.

       Mandatory arguments to long options are mandatory for short options too.

       -e, --echo
	      treat each ARG as an input line

       -i, --input-range=LO-HI
	      treat each number LO through HI as an input line

       -n, --head-count=COUNT
	      output at most COUNT lines

       -o, --output=FILE
	      write result to FILE instead of standard output

       --random-source=FILE
	      get random bytes from FILE

       -z, --zero-terminated
	      end lines with 0 byte, not newline

       --help display this help and exit

       --version
	      output version information and exit

       With no FILE, or when FILE is -, read standard input.

AUTHOR

       Written by Paul Eggert.

REPORTING BUGS

       Report shuf bugs to bug-coreutils@gnu.org
       GNU coreutils home page: <http://www.gnu.org/software/coreutils/>
       General help using GNU software: <http://www.gnu.org/gethelp/>
       Report shuf translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright (C) 2010 Free Software Foundation, Inc.  License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>.
       This is free software: you are free to change and redistribute it.  There is NO WARRANTY, to the extent permitted by law.

SEE ALSO

       The  full documentation for shuf is maintained as a Texinfo manual.  If the info and shuf programs are properly installed at your site, the
       command

	      info coreutils 'shuf invocation'

       should give you access to the complete manual.

GNU coreutils 8.5						   February 2011							   SHUF(1)
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