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Top Forums Programming Perl: How to read from a file, do regular expression and then replace the found regular expression Post 302579120 by jessy83 on Sunday 4th of December 2011 10:36:53 PM
Old 12-04-2011
Perl: How to read from a file, do regular expression and then replace the found regular expression

Hi all,

How am I read a file, find the match regular expression and overwrite to the same files.

Code:
open DESTINATION_FILE, "<tmptravl.dat" or die "tmptravl.dat";
open NEW_DESTINATION_FILE, ">new_tmptravl.dat" or die "new_tmptravl.dat";
while (<DESTINATION_FILE>)
{
# print DESTINATION_FILE_2 "jessy\n";
 chomp($_);
# print "$_ is $hash{$_}\n";
   $line="CLIPPED_PIN_COUNT";
  #  print NEW_DESTINATION_FILE "$_\n";
 #if ($_=~/^$line/)
 if (/^CLIPPED_PIN_COUNT/)
 {
  print "original mathched:",$_,"\n";
  $var=$hash{$line};
  print "var is:",$var,"\n";
#Print out from tmptravl file 
  print "Obtain From tmptravl Fle:",$_,"\n";
#Split out
   @field_new=split/:/,$_;
# print @field;
   push @new_array_new, $field_new[$i];
   print "field",$i,":",$field_new[$i],"\n";
   $i ++;
   push @new_array_new, $field_new[$i];
   print "field",$i,":",$field_new[$i],"\n";
 
#Print out from original file
  print "Obtain From Original File:",$var,"\n";
  s/$_/$field_new[0]:$var/g;
  print "After substituition:",$_,"\n";
  print "-----------------------------------------\n";
         print NEW_DESTINATION_FILE "$_\n";
#   print DESTINATION_FILE,"s/$field_new[$1]/$var/";
#Subsititue original attribute to tmptravl attribue
  close (DESTINATION_FILE);
  close (NEW_DESTINATION_FILE);
 }

}

Do I need to open two file handlers? My purpose is to overwrite the attribute i get from tmptravl.dat and write to new_tmptravl.dat? However, when I write to new_tmptravl.dat, only the new substitution is written in my new_tmptravl.dat? May I know what is the root cause for it?
Thanks.

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Last edited by radoulov; 12-05-2011 at 04:17 PM..
 

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regex(3)						     Library Functions Manual							  regex(3)

Name
       re_comp, re_exec - regular expression handler

Syntax
       char *re_comp(s)
       char *s;

       re_exec(s)
       char *s;

Description
       The  subroutine	compiles  a string into an internal form suitable for pattern matching.  The subroutine checks the argument string against
       the last string passed to

       The subroutine returns 0 if the string s was compiled successfully; otherwise a string containing an  error  message  is  returned.  If	is
       passed 0 or a null string, it returns without changing the currently compiled regular expression.

       The  subroutine 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 and may have trailing or embedded newline characters; they are terminated by	nulls.	 The  regular  expressions
       recognized are described in the manual entry for given the above difference.

Diagnostics
       The subroutine returns -1 for an internal error.

       The subroutine returns one of the following strings if an error occurs:

       No previous regular expression
       Regular expression too long
       unmatched (
       missing ]
       too many () pairs
       unmatched )

See Also
       ed(1), ex(1), egrep(1), fgrep(1), grep(1)

																	  regex(3)
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