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Top Forums Shell Programming and Scripting output redirection to existing file question Post 302573185 by drew211 on Sunday 13th of November 2011 01:07:53 PM
Old 11-13-2011
output redirection to existing file question

So I have a existing file that I used the uniq command on and I need to save the output to the same file without changing the file name.

I have tried $ uniq filename > filename

then when I cat the file it then becomes blank like there is nothing inside.

any help would be much appreciated thanks.

Moderator's Comments:
Mod Comment Double post

Last edited by pludi; 11-13-2011 at 02:35 PM..
 

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UNIQ(1) 							   User Commands							   UNIQ(1)

NAME
uniq - report or omit repeated lines SYNOPSIS
uniq [OPTION]... [INPUT [OUTPUT]] DESCRIPTION
Filter adjacent matching lines from INPUT (or standard input), writing to OUTPUT (or standard output). With no options, matching lines are merged to the first occurrence. Mandatory arguments to long options are mandatory for short options too. -c, --count prefix lines by the number of occurrences -d, --repeated only print duplicate lines, one for each group -D, --all-repeated[=METHOD] print all duplicate lines groups can be delimited with an empty line METHOD={none(default),prepend,separate} -f, --skip-fields=N avoid comparing the first N fields --group[=METHOD] show all items, separating groups with an empty line METHOD={separate(default),prepend,append,both} -i, --ignore-case ignore differences in case when comparing -s, --skip-chars=N avoid comparing the first N characters -u, --unique only print unique lines -z, --zero-terminated end lines with 0 byte, not newline -w, --check-chars=N compare no more than N characters in lines --help display this help and exit --version output version information and exit A field is a run of blanks (usually spaces and/or TABs), then non-blank characters. Fields are skipped before chars. Note: 'uniq' does not detect repeated lines unless they are adjacent. You may want to sort the input first, or use 'sort -u' without 'uniq'. Also, comparisons honor the rules specified by 'LC_COLLATE'. GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report uniq translation bugs to <http://translationproject.org/team/> AUTHOR
Written by Richard M. Stallman and David MacKenzie. COPYRIGHT
Copyright (C) 2013 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
comm(1), join(1), sort(1) The full documentation for uniq is maintained as a Texinfo manual. If the info and uniq programs are properly installed at your site, the command info coreutils 'uniq invocation' should give you access to the complete manual. GNU coreutils 8.22 June 2014 UNIQ(1)
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