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Full Discussion: Match text and print/pipe only that text
Top Forums Shell Programming and Scripting Match text and print/pipe only that text Post 302939918 by durden_tyler on Monday 30th of March 2015 10:37:32 PM
Old 03-30-2015
Quote:
Originally Posted by amx401
...Whenever I use lookbehinds I get no results at all. ex:
Code:
grep -Eo '(?<=")http.*jpg' file
grep -Eo '(?<=\")http.*jpg' file
grep -Eo "(?<!\')http.*jpg' file

...I am still not sure why the lookbehinds didn't work. Please let me know if you have any insight into what I'm doing wrong ...
I have GNU grep and it doesn't work on it.
Most likely grep's "-E" option does not support lookarounds. The man page or the GNU page at: GNU Grep 2.21
do not mention anything about lookarounds.
The "-E" option for "Extended REs" provides the special meaning to metacharacters like "+", "|", "{" etc. unlike BREs.

Code:
$
$ cat f31
http://site.com/image/word/tag/funny"><img src="http://images.site.com/pic/19434-3201cd0ed412e26b2c06cf00a0803c64.jpg
http://images.site.com/uploaded_pics/thumbs/19434.jpg
$
$ grep -E '(?<!")http://images' f31
$
$

If you have GNU grep, you could try the experimental "-P" option which provides support for Perl-compatible regular expressions:

Code:
$
$ grep -Po '(?<!")(http://images.*jp)' f31
http://images.site.com/uploaded_pics/thumbs/19434.jp
$
$

Or you could use Perl:

Code:
$
$ perl -ne 'printf("Line = %d, Matched Text = %s\n", $., $1) if /(?<!")(http:\/\/images.*jpg)/' f31
Line = 2, Matched Text = http://images.site.com/uploaded_pics/thumbs/19434.jpg
$
$

 

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LEARN ABOUT FREEBSD

wildmat

WILDMAT(3)						     Library Functions Manual							WILDMAT(3)

NAME

       wildmat - perform shell-style wildcard matching

SYNOPSIS

       int
       wildmat(text, pattern)
	   char       *text;
	   char       *pattern;

DESCRIPTION

       Wildmat	is  part  of libinn (3).  Wildmat compares the text against the pattern and returns non-zero if the pattern matches the text.  The
       pattern is interpreted according to rules similar to shell filename wildcards, and not as a full regular expression such as  those  handled
       by the grep(1) family of programs or the regex(3) or regexp(3) set of routines.

       The pattern is interpreted as follows:

       x     Turns  off the special meaning of x and matches it directly; this is used mostly before a question mark or asterisk, and is not spe-
	      cial inside square brackets.

       ?      Matches any single character.

       *      Matches any sequence of zero or more characters.

       [x...y]
	      Matches any single character specified by the set x...y.	A minus sign may be used to indicate a	range  of  characters.	 That  is,
	      [0-5abc] is a shorthand for [012345abc].	More than one range may appear inside a character set; [0-9a-zA-Z._] matches almost all of
	      the legal characters for a host name.  The close bracket, ], may be used if it is the first character in the set.  The  minus  sign,
	      -, may be used if it is either the first or last character in the set.

       [^x...y]
	      This  matches any character not in the set x...y, which is interpreted as described above.  For example, [^]-] matches any character
	      other than a close bracket or minus sign.

HISTORY

       Written by Rich $alz <rsalz@uunet.uu.net> in 1986, and posted to Usenet several times since then,  most	notably  in  comp.sources.misc	in
       March, 1991.

       Lars Mathiesen <thorinn@diku.dk> enhanced the multi-asterisk failure mode in early 1991.

       Rich and Lars increased the efficiency of star patterns and reposted it to comp.sources.misc in April, 1991.

       Robert Elz <kre@munnari.oz.au> added minus sign and close bracket handling in June, 1991.

       This is revision 1.10, dated 1992/04/03.

SEE ALSO

       grep(1), regex(3), regexp(3).

																	WILDMAT(3)
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