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Full Discussion: Error redirection question
Top Forums Shell Programming and Scripting Error redirection question Post 302555796 by Corona688 on Thursday 15th of September 2011 03:48:56 PM
Old 09-15-2011
Standard error doesn't pass through pipes. It goes directly to the terminal. So redirecting the last command only redirects errors the last program prints.

Code:
command 2> errlog | command2 | command3

It's extremely wasteful to run awk to process single lines. Might be better to do this:

Code:
[ -r test.dat ] && export LINE_COUNT=`wc -l < test.dat` || echo "Can't read test.dat" >&2

Faster since it uses less processes, and the error messages can be whatever you'd like.
This User Gave Thanks to Corona688 For This Post:
calredd
 

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LEARN ABOUT DEBIAN

plotit

plotit(1)						      General Commands Manual							 plotit(1)

NAME

       plotit - experiment data visualization

SYNOPSIS

       plotit -w FILE
       plotit [-lp] -q FILE [FILE]...
       plotit [-lp] Y FILE [FILE...]
       plotit [-lp] X Y FILE [FILE...]

DESCRIPTION

       The  plotit program is a simple plotting program which can draw line plots and stripcharts using a command language similar to that of gnu-
       plot.  It can also make quick plots of multiple data files from the command-line.  Wildcards may be used in the file names.

       The program takes optional expressions which can be used to manipulate data columns before plotting.  Expressions may be as simple  as  the
       designation  of	a  column  to  be  plotted or may contain arithmetic expressions and functions.  In the latter case the espression must be
       enclosed in 'single' or "double" quotation marks. Column numbers are designated by the at-sign character (@).  A single expression is  used
       for the Y axis of the plot.

OPTIONS

       -h, --help
	      Print the usage and exit.

       --version
	      Print the version number and exit.

       -w     Watch  the input file for commands to stripchart, or wait to read all of stdin before plotting.  Only one file or - for stdin may be
	      specified with this option.  No other options may be used in conjuction with this option.

       -q     Plot the first and second columns of each file.

       -l     Plot with lines.

       -p     Plot with points.

EXAMPLES

       Plot the second column versus the first of all three files with lines only.

	      plotit -lq file1.dat file2.dat file3.dat

       Plot the quotient of the third column and the second column versus the first column of all files matching the pattern using points only.

	      plotit -p '@3/@2' file??.dat

       Plot the natural log of the second column divided by the third column versus the fourth column.	By default these  data	are  plotted  with
       both lines and points.

	      plotit @4 'log(@2/@3)' file.dat

AUTHOR

       This manual page was written by Carlo Segre <segre@iit.edu>.

								 February 21, 2009							 plotit(1)
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