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Perl Program to replace first 3 charaacters of a word in a file

Discussion in 'Perl' started by rag84dec, Sep 29, 2008.

  1. rag84dec

    rag84dec New Member

    Hi all,
    I have a file with some words starting with "RR_"... i want to change it to "TT_"...

    For example.... a word in the file "test.txt" ... is "RR_Word"...i want it to be converted into "TT_Word"... There are 1000 such words in the file.
    I am new to perl so please some one give me any idea??
  2. oogabooga

    oogabooga New Member

    Here it is with line-by-line processing, saving to a different output file:
    open IN, "<test.txt";   # input file
    open OUT, ">test2.txt"; # output file
    while( <IN> ) {       # read a line from IN into $_
        s/\bRR_/TT_/g;    # global substitute on $_
                            # (\b means word boundary)
        print OUT $_;     # write $_ to OUT
    close IN;               # close files
    close OUT;
    If the file is not too big you can change it in place using file-slurping mode:
    undef $/;              # enable file-slurping mode
    open IN, "<test.txt";
    $str = <IN>;           # slurp in whole file
    close IN;
    $str =~ s/\bRR_/TT_/g; # substitute
    open OUT, ">test.txt";
    print OUT $str;        # write whole file
    close OUT;
  3. ungalnanban

    ungalnanban New Member

    Through command line itself we can achieve your requirement.

     $perl -p -i.bak -e "s/RR_/TT_/g;"  test.txt  
    The -i option give the backup file.
    After executing the command you will have the both files "test.txt" and "test.txt.bak" [ RR_WORLD and TT_WORLD ]


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