is this correct

snowrider has asked for the wisdom of the Perl Monks concerning the following question:

fellow monks i think i just found a little mistake i am currently doing the exercise #1 in the tutorials under string matching & regular expressions the original code looks like this

1: #!/usr/bin/perl
2: #this programs prompts a user for a filename and then
3: #replaces all tabs in that file with 3 spaces.
4: print "What file do you want to \"detabify?\" ";
5: $file=<>;
6: chomp $file;
7: $/=undef;             #changes the input record separator so it'll 
+read the entire file in at once
8: open FILE, "<$file";  
9: $text=<FILE>;         #reads the entire file in
10: close FILE;
11: $text=~s/\t/   /g;    #replaces tabs
12: open FILE, ">$file";
13: print $text;          #write changes to file
14: close FILE;
[download]

shouldnt line 12 open $text instead of $file? snowrider

Comment on is this correct Download Code

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Re: is this correct by kschwab (Vicar) on Feb 02, 2001 at 22:28 UTC
It is broken, but not at line 12. Line 13 should read: `print FILE $text;` [download] As it stands now, it reads in the file, prints the untabbified text to STDOUT, and truncates the supplied user-specified file.	[reply] [d/l]
Re: Re: is this correct by PsychoSpunk (Hermit) on Feb 02, 2001 at 22:36 UTC
And assuming you actually run the program, you'll see that problem firsthand and quickly fix that line so it acts correctly. (Note: this is simply a friendly suggestion that some attempt be made to understand the program/problem when you post.) ALL HAIL BRAK!!!	[reply]
Re: Re: Re: is this correct by snowrider (Pilgrim) on Feb 02, 2001 at 22:45 UTC
PsychoSpunk this is my second day tring to program in perl since the program wasnt running correctly i did try to fix the problem but since i dont have any experience in perl thats alittle hard without the help of you guys(fellow monks). thanks for your help snowrider	[reply]
Re: Re: Re: Re: is this correct by Chady (Priest) on Feb 02, 2001 at 23:59 UTC
Re: Re: is this correct by el-moe (Scribe) on Feb 03, 2001 at 05:19 UTC
You could also do this... `select(FILE); print $text; print "blah blah blah\n";` [download] And so on... all prints would go to FILE Update: Snowrider - This is assuming you have multiple files open and are printing to them as you go... and as I know the basic tasks you will have to perform as you come up to speed with Perl... this might be useful to you. i.e., `open DRILL_FILE, ">$drill_file"; open ROUT_FILE, ">$rout_file"; select(DRILL_FILE); print "stuff...\n"; select(ROUT_FILE); print "other stuff...\n";` [download] Prost, Moe	[reply] [d/l] [select]
Re: is this correct by davorg (Chancellor) on Feb 02, 2001 at 22:10 UTC
No, it looks right to me. `$file` contains the name of the file that you are processing and `$text` contains the contents of that file.</p. -- <http://www.dave.org.uk> "Perl makes the fun jobs fun and the boring jobs bearable" - me	[reply]
Re: is this correct by Gloom (Monk) on Feb 03, 2001 at 00:10 UTC
What's append if the file take 150mb of disk space ? Maybe you may use something like this : `# perl -e 'while(<>){s/\t/ /g;print}' < file > file.tmp;\ > mv file.tmp file;` [download] Update : Thank's arhuman for this comment. This option is really usefull. Hope this helps	[reply] [d/l]
Re: Re: is this correct by arhuman (Vicar) on Feb 03, 2001 at 00:15 UTC
In case like this (a `while` loop around one or more files) the `perl -ne` is usually a good candidate... Something like : `perl -ne 's/\t/ /g;print' file > file.tmp; mv file.tmp file;` [download]	[reply] [d/l] [select]
Re: Re: Re: is this correct by repson (Chaplain) on Feb 03, 2001 at 08:20 UTC
To abstract it a little more `perl -i.back -pe 's/\t/ /g' file` The -i means copy original file to `file.back` and put the output of program in `file`. The -p is like -n but does `while(<>){YOUR_CODE; print;}` instead.	[reply] [d/l] [select]


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