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Top Forums Shell Programming and Scripting Need to Speed up shell script Post 302988931 by RudiC on Thursday 5th of January 2017 08:04:00 AM
Old 01-05-2017
Every single redirection opens, reads / writes, and closes the target file. So, for every loop of your script you're handling roughly 80 file operations (times 2, for open and close). Try redirecting the entire script's output, e.g. like
Code:
./script > result.log

.
And, you're running 17 greps per loop, each causing a process creation with its resource consumption, - try running it once with either an alternation search pattern ("PAT1|PAT2|PAT3") or a pattern file (-f option), which would simplify some later treatment, and deal with your pretty print later with e.g. a single sort and / or a single awk command.
 

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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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