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Top Forums Shell Programming and Scripting Arithmetic calculation in variable Post 302789605 by Don Cragun on Thursday 4th of April 2013 01:57:04 AM
Old 04-04-2013
Do you need the contents of var1, or is it just a work variable needed to get the value you want to put into var2? If you just want var2 to be 1 plus the line number of the 1st line in sample.txt that matches the basic regular expression match, calling awk once instead of grep once and cut twice is probably faster:
Code:
var2=$(awk '/match/{print NR + 1; exit}' sample.txt)

but note that when using awk, match is treated as an extended regular expression instead of a basic regular expression. As always, if you're running on a Solaris/SunOS system, use /usr/xpg4/bin/awk or nawk instead of awk.

If you do need the complete list of matching lines, you can keep the way you're currently setting var1, but set var2 just using standard shell parameter expansions:
Code:
var2=$((${var1%% *} + 1))

This should be MUCH MUCH faster than calling cut, xargs, and bc; awk; or cut and expr. This won't work with the original Bourne shell, but works with any POSIX conforming shell (such as bash or a 1993 or later version of ksh).
 

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GREP(1) 						      General Commands Manual							   GREP(1)

NAME
grep, g - search a file for a pattern SYNOPSIS
grep [ option ... ] pattern [ file ... ] g [ option ... ] pattern [ file ... ] DESCRIPTION
Grep searches the input files (standard input default) for lines that match the pattern, a regular expression as defined in regexp(7) with the addition of a newline character as an alternative (substitute for |) with lowest precedence. 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. -e The following argument is taken as a pattern. This option makes it easy to specify patterns that might confuse argument parsing, such as -n. -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. -f The pattern argument is the name of a file containing regular expressions one per line. -b Don't buffer the output: write each output line as soon as it is discovered. 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 '...'. An expression starting with '*' will treat the rest of the expression as literal characters. G invokes grep with -n and forces tagging of output lines by file name. If no files are listed, it searches all files matching *.C *.b *.c *.h *.m *.cc *.java *.cgi *.pl *.py *.tex *.ms SOURCE
/src/cmd/grep /bin/g SEE ALSO
ed(1), awk(1), sed(1), sam(1), regexp(7) 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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