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.
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)