awk last n lines of file Post: 302905878

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Top Forums Shell Programming and Scripting awk last n lines of file Post 302905878 by Don Cragun on Sunday 15th of June 2014 06:42:31 PM

06-15-2014

Registered User

I agree with RudiC. Your code:

Code:

head -c 10K >> /home/uplog.txt | awk 'END{print NR " swap " NF$5; exit}' /home/uplog.txt;

doesn't seem to be related to what you said you're trying to do. This code (depending on what OS you're using) will give you a diagnostic for an invalid head -c option-argument, a diagnostic saying that head doesn't have a -c option, or append the 1st 10000 or 10240 characters from standard input for this script to the end of /home/uplog.txt while simultaneously having awk read whatever it finds in /home/uplog.txt and then print the number of lines it found in the file (before head started adding data to it, at some point in time while head is writing to it, or after head has finished writing to it) followed by the string swap followed by (depending on what OS you're using) the number of fields in the last record in the file and the contents of the 5th field from the last line of the file, nothing, or one but not both of those values.

Your requirements are ambiguous.

Limiting a file to 200 lines from the outset is not the same thing as reading it at some later time and discarding all but the 1st 10k characters (without checking for line boundaries).

Please give us a clear English description of what you are trying to do.

Don Cragun

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LEARN ABOUT DEBIAN

head

HEAD(1) 							   User Commands							   HEAD(1)

NAME

       head - output the first part of files

SYNOPSIS

       head [OPTION]... [FILE]...

DESCRIPTION

       Print  the first 10 lines of each FILE to standard output.  With more than one FILE, precede each with a header giving the file name.  With
       no FILE, or when FILE is -, read standard input.

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

       -c, --bytes=[-]K
	      print the first K bytes of each file; with the leading `-', print all but the last K bytes of each file

       -n, --lines=[-]K
	      print the first K lines instead of the first 10; with the leading `-', print all but the last K lines of each file

       -q, --quiet, --silent
	      never print headers giving file names

       -v, --verbose
	      always print headers giving file names

       --help display this help and exit

       --version
	      output version information and exit

       K may have a multiplier suffix: b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P,
       E, Z, Y.

AUTHOR

       Written by David MacKenzie and Jim Meyering.

REPORTING BUGS

       Report head 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 head translation bugs to <http://translationproject.org/team/>

COPYRIGHT

       Copyright (C) 2011 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 head is maintained as a Texinfo manual.  If the info and head programs are properly installed at your site, the
       command

	      info coreutils 'head invocation'

       should give you access to the complete manual.

GNU coreutils 8.12.197-032bb					  September 2011							   HEAD(1)