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Multi pattern match

Posted on 2001-07-31
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Last Modified: 2008-02-01
UNIX has a "-E" switch to allow its grep utility to match multiple patterns at once, eg:
  grep -E "abc|def|ghi|jkl" infile
will match all lines in infile which contain "abc" or "def", etc.

I know Perl has a "grep" command, and I know it can also do pattern matching with the "=~" operator, but how can I write CONCISE Perl code to match multiple patterns with the:
1. grep command?
2. "=~" operator?

Thanks.
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Question by:tel2
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LVL 84

Expert Comment

by:ozo
ID: 6339110
print grep /abc|def|ghi|jkl/ <>;
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Expert Comment

by:ozo
ID: 6339119
print grep /abc|def|ghi|jkl/,<>;
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Author Comment

by:tel2
ID: 6343456
ozo,

Is this an answer to both questions, or just #1?  If just #1, are there any other commands (eg: "=~") which allow for multiple pattern matching, if so, please give examples.

What does the "<>" mean exactly?
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Accepted Solution

by:
ozo earned 30 total points
ID: 6345384
while( defined($strimg = <>) ){
    print $string if $string =~ /abc|def|ghi|jkl/;
}


perldoc -f readline
                 readline EXPR
                         Reads   from  the  filehandle  whose  typeglob  is
                         contained in EXPR.  In scalar context,  each  call
                         reads and returns the next line, until end-of-file
                         is reached, whereupon the subsequent call  returns
                         undef.   In  list context, reads until end-of-file
                         is reached and returns a list of lines.  Note that
                         the  notion  of  ``line'' used here is however you
                         may    have    defined    it    with     $/     or
                         $INPUT_RECORD_SEPARATOR).  See the section on "$/"
                         in the perlvar manpage.
                         When $/ is set to undef,  when  readline()  is  in
                         scalar context (i.e. file slurp mode), and when an
                         empty file is read, it returns '' the first  time,
                         followed by undef subsequently.
                         This  is  the  internal  function implementing the
                         <EXPR> operator, but you can use it directly.  The
                         <EXPR> operator is discussed in more detail in the
                         I/O Operators entry in the perlop manpage.
                             $line = <STDIN>;
                             $line = readline(*STDIN);           # same thing

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Author Comment

by:tel2
ID: 6374742
ozo,

Thanks for that.
So, are you saying that "<>" is the same as "readline"?
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