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Top Forums Shell Programming and Scripting Comparing alternate lines of code Post 303025784 by cabled on Monday 12th of November 2018 09:56:51 AM
Old 11-12-2018
Comparing alternate lines of code

Hi gents,

Have only a passing familiarity with linux/shell at this point, so please forgive simple question.

I have text files that have lines something like the following:

Code:
a
b
c
d
d
d
e
f
e
f
e
f
a
b
c
d
e
f
etc

I'm trying to remove 2 types of duplicates while preserving line order/format.
1) consecutive duplicate lines
2) alternate lines if they are duplicate

For removing type 1 lines,
Code:
cat "$file" | uniq > ./output/"$file"

gives me an output file that looks like

Code:
a
b
c
d
e
f
e
f
e
f
a
b
c
d
e
f
etc

which is fine.

I'm kinda stumped about type 2 duplicates though...

Ideally I'd like to get:

Code:
a
b
c
d
e
f
a
b
c
d
e
f

Not entirely sure how to compare alternate lines... Any assistance is appreciated

Last edited by RudiC; 11-12-2018 at 11:06 AM..
 

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GREP(1) 						      General Commands Manual							   GREP(1)

NAME
grep - search a file for a pattern SYNOPSIS
grep [ option ... ] pattern [ file ... ] DESCRIPTION
Grep searches the input files (standard input default) for lines (with newlines excluded) that match the pattern, a regular expression as defined in regexp(6). Normally, each line matching the pattern is `selected', and each selected line is copied to the standard output. The options are -c Print only a count of matching lines. -h Do not print file name tags (headers) with output lines. -i Ignore alphabetic case distinctions. The implementation folds into lower case all letters in the pattern and input before interpre- tation. Matched lines are printed in their original form. -l (ell) Print the names of files with selected lines; don't print the lines. -L Print the names of files with no selected lines; the converse of -l. -n Mark each printed line with its line number counted in its file. -s Produce no output, but return status. -v Reverse: print lines that do not match the pattern. Output lines are tagged by file name when there is more than one input file. (To force this tagging, include /dev/null as a file name argument.) Care should be taken when using the shell metacharacters $*[^|()= and newline in pattern; it is safest to enclose the entire expression in single quotes '...'. SOURCE
/sys/src/cmd/grep.c SEE ALSO
ed(1), awk(1), sed(1), sam(1), regexp(6) DIAGNOSTICS
Exit status is null if any lines are selected, or non-null when no lines are selected or an error occurs. GREP(1)
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