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Full Discussion: Grepping for Exact Strings
Top Forums Shell Programming and Scripting Grepping for Exact Strings Post 302308839 by Gunther on Monday 20th of April 2009 11:46:02 AM
Old 04-20-2009
@quirkasaurus: The pipe is the alternating operator, demanding that either the expression on the left or on the right has to be met. In this particular regex it means that the string "airplane" starts straightaway or after a whitespace character (\s). The whitespace char then, however, would not be in the regex result because of the "?<=" sequence. That is called positive lookbehind meaning that after a whitespace the string "airplane" has to be found.
You've got something similiar at the end of the regex: This time we're dealing with a positiv lookahead assertion, though. Additionally, the pipe operator is there one again, telling that the expression has to be followed by a whitespace char (lookahead) or ends right away ($).

@devtakh: Unfortunately, it's not changing anything. What's the use of the escaped angle brackets?
If you want to go with awk you could use my script in a for loop. Each iteration then sets a new character as input field separator and output field separator.
But hopefully, someone will provide a more elegant solution Smilie
 

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RE_COMP(3)						     Linux Programmer's Manual							RE_COMP(3)

NAME
re_comp, re_exec - BSD regex functions SYNOPSIS
#define _REGEX_RE_COMP #include <sys/types.h> #include <regex.h> char *re_comp(char *regex); int re_exec(char *string); DESCRIPTION
re_comp() is used to compile the null-terminated regular expression pointed to by regex. The compiled pattern occupies a static area, the pattern buffer, which is overwritten by subsequent use of re_comp(). If regex is NULL, no operation is performed and the pattern buffer's contents are not altered. re_exec() is used to assess whether the null-terminated string pointed to by string matches the previously compiled regex. RETURN VALUE
re_comp() returns NULL on successful compilation of regex otherwise it returns a pointer to an appropriate error message. re_exec() returns 1 for a successful match, zero for failure. ATTRIBUTES
Multithreading (see pthreads(7)) The re_comp() and re_exec() functions are not thread-safe. CONFORMING TO
4.3BSD. NOTES
These functions are obsolete; the functions documented in regcomp(3) should be used instead. SEE ALSO
regcomp(3), regex(7), GNU regex manual COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. GNU
2013-06-21 RE_COMP(3)
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