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Top Forums Shell Programming and Scripting echo command and file I/O Redirection Post 302193596 by userix on Saturday 10th of May 2008 12:23:23 AM
Old 05-10-2008
echo command and file I/O Redirection

I have a colon-delimited text file of names, addresses and phone numbers. I am trying to write a script that can add additional entries and then sort it alphabetical by last name and resave it to the original file. I am using C shell to script. This is the section of my script that I wish to sort the data file and then save it to itself:

Code:
set file = `sort -k1,2 $myfile`
echo $file > $myfile

This code works and does sort, but the problem comes when I try to echo the sorted data back into the original file. Echo apparently does not show the original newline characters, so the updated file I get no longer is sorted by rows, but rather one continuous string. Or the problem could lie in the setting of the 'file' variable, in which newline characters are not set into the variable 'file' as well. I have tried another method using the following code:

Code:
sort -k1,2 $myfile > 0
cat 0 > $myfile
rm 0

Basically above, instead of using the echo command, I actually redirect the sorted output to a temporary file called '0' and then cat it back, overwriting the original contents of $myfile. While this method works, it requires that I temporarily create the '0' file.

My underlining question is: How can I sort the data file and then save it back into itself without having to create a temporary file '0' and still have the newline characters that separate each row remain? Thanks

Last edited by userix; 05-10-2008 at 01:43 AM..
 

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Perl::Critic::Policy::Subroutines::ProhibitReturnSort(3pUser Contributed Perl DocumentatPerl::Critic::Policy::Subroutines::ProhibitReturnSort(3pm)

NAME
Perl::Critic::Policy::Subroutines::ProhibitReturnSort - Behavior of "sort" is not defined if called in scalar context. AFFILIATION
This Policy is part of the core Perl::Critic distribution. DESCRIPTION
The behavior of the builtin "sort" function is not defined if called in scalar context. So if you write a subroutine that directly "return"s the result of a "sort" operation, then you code will behave unpredictably if someone calls your subroutine in a scalar context. This Policy emits a violation if the "return" keyword is directly followed by the "sort" function. To safely return a sorted list of values from a subroutine, you should assign the sorted values to a temporary variable first. For example: sub frobulate { return sort @list; # not ok! @sorted_list = sort @list; return @sort # ok } KNOWN BUGS
This Policy is not sensitive to the "wantarray" function. So the following code would generate a false violation: sub frobulate { if (wantarray) { return sort @list; } else{ return join @list; } } CONFIGURATION
This Policy is not configurable except for the standard options. CREDITS
This Policy was suggested by Ulrich Wisser and the <http://iis.se> team. AUTHOR
Jeffrey Ryan Thalhammer <jeff@imaginative-software.com> COPYRIGHT
Copyright (c) 2005-2011 Imaginative Software Systems. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module. perl v5.14.2 2012-06-07 Perl::Critic::Policy::Subroutines::ProhibitReturnSort(3pm)
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