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Top Forums UNIX for Dummies Questions & Answers Exact match with regular expression Post 302232933 by jdhahbi on Friday 5th of September 2008 02:49:43 PM
Old 09-05-2008
Exact match with regular expression

Hi
I have a file with data arranged into columns. The first column is the chromosome name.
When I use grep to subset only rows with chr1, I get chr1 but also chr10, chr11,..
How do I get only rows with chr1?

grep chr1 filein > fileout
head fileout
chr1 59757841
chr11 108258691
chr10 86158268
chr12 112891635

thanks
Joseph
 

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REGEX(3)						     Library Functions Manual							  REGEX(3)

NAME
re_comp, re_exec - regular expression handler SYNOPSIS
char *re_comp(s) char *s; re_exec(s) char *s; DESCRIPTION
Re_comp compiles a string into an internal form suitable for pattern matching. Re_exec checks the argument string against the last string passed to re_comp. Re_comp returns 0 if the string s was compiled successfully; otherwise a string containing an error message is returned. If re_comp is passed 0 or a null string, it returns without changing the currently compiled regular expression. Re_exec returns 1 if the string s matches the last compiled regular expression, 0 if the string s failed to match the last compiled regular expression, and -1 if the compiled regular expression was invalid (indicating an internal error). The strings passed to both re_comp and re_exec may have trailing or embedded newline characters; they are terminated by nulls. The regular expressions recognized are described in the manual entry for ed(1), given the above difference. SEE ALSO
ed(1), ex(1), egrep(1), fgrep(1), grep(1) DIAGNOSTICS
Re_exec returns -1 for an internal error. Re_comp returns one of the following strings if an error occurs: No previous regular expression, Regular expression too long, unmatched (, missing ], too many () pairs, unmatched ). 3rd Berkeley Distribution May 15, 1985 REGEX(3)
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