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Full Discussion: How to make awk command faster for large amount of data?
Top Forums Shell Programming and Scripting How to make awk command faster for large amount of data? Post 303024270 by disedorgue on Friday 5th of October 2018 03:49:45 AM
Old 10-05-2018
Quote:
Originally Posted by Don Cragun
It might, or might not, be faster depending on what hardware you're using, what operating system you're using, what version of perl you're using, and what other tools you're using as a comparison. But, note that even though this is only printing the first and last lines of the compressed file, it can't avoid reading the entire compressed file and uncompressing all of the compressed data to be able to determine the contents of the last line in the file. (Decompression can't start at random places in the file; it must start at the beginning and progress byte by byte from there.)
I know all that, but there may be a significant gain because we only create the process once instead of creating 4 * n file.
Where I have a doubt is that perl does not emulate seek by just passing through a memory buffer.
 

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LEARN ABOUT AIX

zcat

Commands Reference, Volume 6, v - z

zcat_Command

  Purpose

   Expands a compressed file to standard output.

  Syntax

   zcat [  -n ] [  -V ] [  File ... ]

  Description

   The	zcat  command  allows  the user to expand and view a com-
pressed file
   without uncompressing that file. The zcat command does not re-
name the
   expanded  file  or  remove  the .Z extension. The zcat command
writes the
   expanded output to standard output.

  Flags

   -n	 Omits the compressed file  header  from  the  compressed
file.
   -V	  Writes the current version and compile options to stan-
dard error.

  Parameters

   File ...		Specifies the compressed files to expand.

  Return Values

   If the zcat command exits with a status of 1  if  any  of  the
following
   events occur:

     * The input file was not produced by the compress command.
     *	An  input file cannot be read or an output file cannot be
written.

   If no error occurs, the exit status is 0.

  Exit Status

   0			       Successful completion.
   >0			       An error occurred.

  Examples

   To view the foo.Z file without uncompressing it, enter:

	 zcat foo.Z

   The uncompressed contents of the foo.Z  file  are  written  to
standard
   output. The file is not renamed.

  Related Information

   The compress command, pack command, uncompress command,
   unpack command.

   Commands in Operating system and device management.

________________________________________________________________________________

		      Commands Reference, Volume 6, v - z

zcat_Command

  Purpose

   Expands a compressed file to standard output.

  Syntax

   zcat [  -n ] [  -V ] [  File ... ]

  Description

   The zcat command allows the user to expand  and  view  a  com-
pressed file
   without uncompressing that file. The zcat command does not re-
name the
   expanded file or remove the .Z  extension.  The  zcat  command
writes the
   expanded output to standard output.

  Flags

   -n	  Omits  the  compressed  file header from the compressed
file.
   -V	 Writes the current version and compile options to  stan-
dard error.

  Parameters

   File ...		Specifies the compressed files to expand.

  Return Values

   If  the  zcat  command  exits with a status of 1 if any of the
following
   events occur:

     * The input file was not produced by the compress command.
     * An input file cannot be read or an output file  cannot  be
written.

   If no error occurs, the exit status is 0.

  Exit Status

   0			       Successful completion.
   >0			       An error occurred.

  Examples

   To view the foo.Z file without uncompressing it, enter:

	 zcat foo.Z

   The	uncompressed  contents	of  the foo.Z file are written to
standard
   output. The file is not renamed.

  Related Information

   The compress command, pack command, uncompress command,
   unpack command.

   Commands in Operating system and device management.
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