| 1 |
Regular expressions should be familiar as they are used in many UNIX commands with grep as best known
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grep pattern file; # Prints out each line of file containing pattern
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| 2 |
The rules for pattern are rich and we will discuss later -- consider here the simple pattern Fox
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| 3 |
Then we can write the PERL version of grep as follows:
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| 4 |
$line =0;
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| 5 |
while (<>) {
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if( /Fox/ ) { # Generalize to /Pattern/ to test positive if Pattern in $_
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print $line, "$_"; } # $_ is current line by default
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$line++; }
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| 6 |
Another familiar operator should be s in sed (the batch or stream line editor) where
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| 7 |
s/Pattern1/Pattern2/; # substitutes Pattern1 by Pattern2 in each line
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| 8 |
The same command can be used in PERL with again substitution occuring on $_
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