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Perl File Handling: open, read, write and close files

This article describes the facilities provided for Perl file handling.

Opening files

Opening a file in perl in straightforward: open FILE, "filename.txt" or die $!; The command above will associate the FILE filehandle with the file filename.txt. You can use the filehandle to read from the file. If the file doesn't exist - or you cannot read it for any other reason - then the script will die with the appropriate error message stored in the $! variable.

What if you wanted to modify the file instead of just reading from it? Then you'd have to specify the appropriate mode using the three-argument form of open. open FILEHANDLE, MODE, EXPR The available modes are the following:

mode operand create truncate
read <
write > ✓ ✓
append >> ✓

Each of the above modes can also be prefixed with the + character to allow for simultaneous reading and writing.

mode operand create truncate
read/write +<
read/write +> ✓ ✓
read/append +>> ✓

Notice, how both +< and +> open the file in read/write mode but the latter also creates the file if it doesn't exist or truncates (deletes) an existing file. So, if you wanted to open a file for writing, creating it if it doesn't exist and truncating it first if does, you'd do the following: open FILE, ">", "filename.txt" or die $! This operation might fail if for example you don't have the appropriate permissions. In this case $! will be set appropriately.

The mode and the filename in the three-argument form can be combined, so the above can also be written as: open FILE, ">filename.txt" or die $!; As you might have guessed already if you just want read access you can skip the mode just as we did in the very first example above.

Reading files

If you want to read a text file line-by-line then you can do it as such: my @lines = <FILE>; The <FILE> operator - where FILE is a previously opened filehandle - returns all the unread lines of the text file in list context or a single line in scalar context. Hence, if you had a particularly large file and you wanted to conserve memory you could process it line by line: while (<FILE>) { print $_; } The $_ variable is automatically set for you to the contents of the current line. If you wish you may name your line variable instead: while (my $line = <FILE>) { ... will set the $line variable to the contents of the current line. The newline character at the end of the line is not removed automatically. If you wish to remove it you can use the chomp command. After all lines have been read the <FILE> operator will return a false value hence causing the loop to terminate.

There may cases where you need to read a file only a few characters at a time instead of line-by-line. This may be the case for binary data. To do just that you can use the read command. open FILE, "picture.jpg" or die $!; binmode FILE; my ($buf, $data, $n); while (($n = read FILE, $data, 4) != 0) { print "$n bytes read\n"; $buf .= $data; } close(FILE); There is a lot going on here so let's take it step by step. In the first line of the above code fragment a file is opened. As you can guess from the filename it is a binary file. Binary files need to treated differently than text files on some operating systems (eg, Windows). The reason is that on these platforms a newline "character" is actually represented within text files by the two character sequence \cM\cJ (that's control-M, control-J). When reading the text file Perl will convert the \cM\cJ sequence into a single \n newline characted. The converse also holds when writing files. Clearly, when reading binary data this behavior is undesired and calling binmode on the filehandle will make sure that this conversion is avoided.

The read command takes either 3 or 4 arguments. The 3-argument form is: read FILEHANDLE, SCALAR, LENGTH while the 4-argument form is: read FILEHANDLE, SCALAR, LENGTH, OFFSET In the first case LENGTH characters of data are read in the variable specified by SCALAR from FILEHANDLE. The return value of read is the number of characters actually read, 0 at the end of the file or undef in the case of an error. Returning to our example above the third line of code will read at most 4 characters of data into the $data variable. The number of characters read will be stored in $n. Successive read operations on the same filehandle will set the current file position to be just before the first unread character. Thus the code above will read the contents of the file picture.jpg and store them in $buf, printing the number of characters read at every iteration.

If OFFSET is specified then the characters read will be placed at that position within the SCALAR. Taking advantage of this we could rewrite the loop above as such: my ($data, $n, $offset); while (($n = read FILE, $data, 4, $offset) != 0) { print "$n bytes read\n"; $offset += $n; }

Even though the example above demonstrates binary reading the read command works just as well on text files - just make sure to use (for binary) or not use (for text) binmode accordingly.

Writing files

Now that you know how to open and read files learning how to write to them is straighforward. Take a look at the following code: open FILE, ">file.txt" or die $!; print FILE $str; close FILE; Not much is new here. The only thing to observe is the two-argument use of print, the first argument being the FILEHANDLE to write to and the second an expression to be written. The expression can be anything: a scalar, a list, a hash, etc. Appending to a file can be accomplished in exactly the same manner - apart from specifying the appropriate (>>) mode of course.

At this point you are probably thinking that a description of the write is what follows. Actually, as the manual page for write puts it:
Note that write is not the opposite of read. Unfortunately.
Instead write is used to write formatted records to file, a subject outside the scope of this article.

Closing files

Once you are done reading and writing you should close any open filehandles. open FILE1, "file.txt" or die $!; open FILE2, "picture.jpg" or die $!; ... close FILE2; close FILE1; If you forget to close a filehandle Perl will do it for you before your script exists but it is good practice to close yourself what you have opened.

The close command may also fail returning false, eg, if you try to close a closed filehandle. If you want to catch these errors you can check the return value of close and the approriate error message stored in $! as is done in the following example: close FILE or die $!

Summary of perl file handling

The open, close, print and read commands will allow you to perform most common file operations. However, much more is possible. Apart from opening files you may open pipes to other commands using the | mode and read from them or write to them using the techniques described. This and more in an article to come.

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Comments

David   

Posted at 6:38am on Tuesday, June 26th, 2007

Cool tutorials but the perl installation file. havidworld@yahoo.co.nz

fountain_spray   

Posted at 12:50pm on Wednesday, June 27th, 2007

Not describing Format for Write is a cop-out!

Where do I turn for THAT tutorial?

Richard Wicks   

Posted at 4:11pm on Thursday, August 23rd, 2007

Well, great, I can read binary files now. How the heck do I write them?

Tobias Maier   

Posted at 7:13am on Thursday, August 30th, 2007

You can use 'pack' to write binary files.
E.g.: The following snippet writes all numbers between 0 and zero as unsigned characters.

open(BIN, '>', 'binary_file')
or die "Couldn't open file for writing: $!n";
foreach my $i (0 ... 255) {
print BIN pack('C', $i);
}
close BIN;

Jo   

Posted at 9:09am on Monday, September 24th, 2007

I need to be able to read the first 20 lines of a txt file. How about that.
@ARGV?

Richard   

Posted at 2:57pm on Tuesday, September 25th, 2007

open(FILE, "

Richard   

Posted at 2:59pm on Tuesday, September 25th, 2007

open(FILE, "

Richard   

Posted at 3:00pm on Tuesday, September 25th, 2007

Sorry, I don't know why it won't take my entire comment :(

Sasi   

Posted at 9:25am on Monday, October 1st, 2007

I have a hash variable with 10K records and I want to write 1000 records at one shot into the file. Is there a way in perl?

Clement   

Posted at 1:42pm on Monday, October 1st, 2007

Thanks for this site, it is really good. If I want to read several files such as c_1, c_2, c_3 etc in the same directory, how do I write the perl script to do this for me. Please, you could send me a response to agclems@yahoo.com Many thanks for your help.

Regards,

Clement.

Salvor   

Posted at 12:47am on Tuesday, October 23rd, 2007

I think it's better to write here and not send you a private response. Anyelse can read it, so:

my $i=1;
while (-e "c_$i"){
open (FILE, "c_$i") || die ("What the hell??? Can't open c_$i!!!");
my @lines = ;
close FILE;
doincrediblethingswhiththe(@lines);
$i++;
}

Salvor   

Posted at 12:50am on Tuesday, October 23rd, 2007

Sorry, the forum eat some of my comment. 4th line:
my @lines = <FILE>;

well, you know, read all file into an array, as explained before in this page.

Regards.

Norton   

Posted at 7:13am on Wednesday, November 21st, 2007

I would really like to see how can you store the contents of the file in an array, where lines are appended as array elements.

Could you please add it to this tutorial?
Cheers, Norton

Johan   

Posted at 4:17am on Friday, December 7th, 2007

Norton: to add a file to an array,

@array = ;

should do the trick.

harsh   

Posted at 8:55am on Thursday, December 13th, 2007

read multiple files from same directory
opendir DIR, "C:/perl/bin/1" || die "Cannot opendir 1 $!";
while ( $filename = readdir(DIR) ) {
if($filename=~/.*.htm/){
open IN, "C:/perl/bin/1/$filename";
open OUT,">>C:/perl/bin/1/all.txt";
while(){ chomp ($_);
and so on}

by using this you can read multiple files from directory 1 and write all the files in a new file.

regards
harsh

Jared   

Posted at 9:19am on Wednesday, December 19th, 2007

This:
foreach my $i (0 ... 255) {
print BIN pack('C', $i);
}

Could also be written as:

print BIN map(pack($_),@{[0..255]});

:)

cris   

Posted at 10:37am on Wednesday, December 26th, 2007

how do you open a image and print it?

Nikhil   

Posted at 2:52pm on Saturday, December 29th, 2007

How do you search for a pattern and then delete all the lines above and below it?
eg
abbbbbbbbbcioiheiodnweiniwqoed
Serial Number
iuawheiuhoiehoqwiheeewq

I want to search for Serial Number and delete all three lines..
I want to repeat this all over the file wherever the Serial Number occurs..

kumar   

Posted at 12:06pm on Thursday, January 3rd, 2008

I need a script for the below task.I have a txt file with xxxxx numbers , one number each line.
I should run a perl script so that my script should read this txt file line 1 and then line 2 , then line 3 etc till the predefined match is found.I wanna use this line 1 value in the command executed below this script.this command output should be updated to a new file always.
Obiliged if any answers for my query.

SK Rahman   

Posted at 4:49am on Friday, January 4th, 2008

if i run the following script i am getting a binary file
but when i open with hex editor
i am able see that the actual numbers are

"01 02 03 04 05 06 07 08 09"
what i wanted output like this
"12 34 56 78"
please help me to write a script for this...
thanks in advance


open(BIN, '>', 'binary_file')
or die "Couldn't open file for writing: $!n";

foreach my $i (1 ... 9)
{
binmode BIN;
print BIN pack('C', $i);
}
close BIN;

ZwribMaster   

Posted at 6:39pm on Thursday, January 17th, 2008

Hi, I want to try to open a file, and if it fails, I want to write the filename to a log file but continue on with my program to open the other files in my list. Is there an alternative to using open the file || or die?

ZwribMaster   

Posted at 6:52pm on Thursday, January 17th, 2008

Hi Nikhil,

You can read the file contents into an array, and then use a foreach loop to scan each line of the array. For ex:

open(PAGE,"yourfile.txt") || die "I can't open yourfile.txt";
#store the contents of the file into the File array
@File = ;
close(PAGE);
$Ctr = 0;

#then loop through the file...
foreach (@File){
if ($File[$Ctr] =~ m/SerialNumber/){
#remove the 3 lines from the array
$File[$Ctr] = "";
$File[$Ctr+1] = "";
$File[$Ctr-1] = "";
}
$Ctr = $Ctr+1; #increment through the rest of array

} #end foreach

#write the array contents to the file...
open(PAGE,">yourfile.txt") || die "I can't open yourfile.txt"; #open the file to read
print PAGE @File;
close(PAGE);

Dave   

Posted at 8:51am on Sunday, January 20th, 2008

I'm trying to load a txt file into an array and filter out specific data. I used ZwribMaster post as a template and it has helped a lot. I have one issue. Instead of removing the lines from the array, it is just replacing them with a blank space. Here is sample of what I'm running:


#Open and Load Input file to array
open INPUT_FILE, "data.txt" or die $!;
print OUTPUT_FILE "@Data";
close OUTPUT_FILE;

Any help would be appreciated,,

Thanks,
Dave C

DaveC   

Posted at 11:24am on Sunday, January 20th, 2008

It's seems my script was cut off in my last post.


#Open and Load Input file to array
open INPUT_FILE, "data.txt" or die $!;
print OUTPUT_FILE "@Data";
close OUTPUT_FILE;

Sai Ram   

Posted at 9:52pm on Monday, January 21st, 2008

How to make use oF APIs in perl..please help me out...i am lost becoz of this.. :-(
I need this immediately...

Sylvia   

Posted at 8:05am on Tuesday, January 29th, 2008

Hi there!
I would like to print the same content to 4 output files at the same time, is there anyway to do this, or do I have to do it on four separate lines?

eg
print FILE_1 "example";
print FILE_2 "example";
print FILE_3 "example";
print FILE_4 "example";

can I do something like this?
print {FILE_1 FILE_2 FILE_3 FILE_4} "example";

thanks for your help

Kiran   

Posted at 2:24am on Friday, February 1st, 2008

Hi Friends!! I need to write a script which will logon to sftp server & then check for files in a particular directory if the file is present it should append that file is present ina text file if not it should append file not present how this can be achieved i am stuck up at logging on to sftp server please help thanks in advance

Kiran   

Posted at 11:23pm on Wednesday, February 13th, 2008

Hi,
I have 2 files, say file1 & file2. I have some, variable in file1 say $work. I want to read this in file2 & use it in file2.
Could anyone help me in this
Thanks
Kiran

Rich   

Posted at 8:39pm on Saturday, February 23rd, 2008

Kiran, regarding your question on the thirteenth, simply open both files, and copy the $work to file2.

Kiran   

Posted at 2:46am on Monday, February 25th, 2008

Guys can any body help me on question posted on 1st feb 08
" need to write a script which will logon to sftp server & then check for files in a particular directory if the file is present it should append that file is present ina text file if not it should append file not present how this can be achieved i am stuck up at logging on to sftp server please help thanks in advance"

Torsten   

Posted at 3:17am on Friday, March 14th, 2008

Hi,

I have the following problem:
I want to open a file and read its content into a variable.
After that a standard input should be read into another variable. But after this input, the script gets stuck.
If I swap both, the script works. Here a part of my script:

open FILE, "c:/tmp/mail_receivers.txt" or die "Couldn't open: $!";
local $/;
$receiver = ;
close FILE;
print ("nPlease enter mail subject.");
$subject = ;
print ("nSubject: $subject");
print("$receiver");

Can anybody help me?
Thanks,
Torsten

Bassir   

Posted at 11:23pm on Sunday, March 16th, 2008

i have too many problems with doing an algorithm

Manojg   

Posted at 11:23am on Wednesday, March 19th, 2008

Hi,

I tried to open a file by using

open FILE, ">", "filename.txt" or die $!

The script did not give any error and there was no any file opened. Where does it open the file? in memory? How do I open a file in disk?

Thanks.

Shruthi   

Posted at 1:12am on Monday, March 24th, 2008

How do i write perl script for reading a file and how i can see output from this.
If any body knows please send it back as comments in this same page.

Suresh,S   

Posted at 1:44am on Monday, March 24th, 2008

created a excel sheet as Book1.xls

just tried this coding for opening Book1.xls unable to open the excel file the output is coming in Dos prompt itself why?

#!/usr/local/bin/perl
open (MYFILE, 'Book1.xls');
while () {
chomp;
print "$_n";
}
close (MYFILE);

Just reply the solution Immediately

Jacob   

Posted at 11:24am on Wednesday, April 2nd, 2008

Hi all..

Im trying to make this littel hash cracker in perl (JTR dosent take saltet hash), and it works fine, but now i want it to goto next hash, when it finds a correct password, insted of trying the intire paasword list.. (aka for more speed)

The script looks like this:

#!/usr/bin/perl

use Digest::MD5 qw(md5_hex);
use Data::Dumper;

open(FH0, " < digits"); #long list of passwords
while(){
chomp;
($password,$b) = split(/:/);

open(FH1, "< alle1"); #long list of hash
while() {
chomp;
($last,$hash,$salt,$mail) = (split(/:/))[0,1,2,3]; {

open (FH2, '>>data.txt');
print FH2 "$mail:$passwordn" if(md5_hex($salt.$password) eq $hash);

# print "BINGO CHAMPn" if(md5_hex($salt.$password) eq $hash);
# print "$passwordn";
}
}
}
close(FH0);
close(FH1);
close(FH2);

Can someone help me whit that?

Pramod Badgujar   

Posted at 10:17pm on Tuesday, April 8th, 2008

How to replace the content of line with the another text?

Pramod Badgujar   

Posted at 10:22pm on Tuesday, April 8th, 2008

How to replace the content of line with the another text?
Please give me answer of the above question.

emma   

Posted at 9:10am on Friday, April 11th, 2008

Hi all,

I am new to Perl scripting and need your help.
Here is the problem I am having .

I have a file with some strings each delimited by a "|'character.
I have to open the file , each each line and replace the '|' with a tab or space and then copy them to to a file.
Eg: file ABC
Contents are as follows -
asdfd|||sdhh||sdghhgd|||
afsgasfd||asdsadsad|adff||||||fasffasf|
etc
Desired output

asdfd sdkjf dsfhdh
sffhjd djfhjhds dhfjhfjh (ie no "|" characters.)

I appreciate your help.
Please some one help me with the perl code to do this task . I am sure it is easy job for perl experts.

Bharath   

Posted at 6:42pm on Monday, April 21st, 2008

Hi,

I want to open an image and see the binary values of that image.Is there a way to open an jpeg or png or bmp file and prints the contents of that file in zeroes and ones using perl.

Thanks in advance,
Bharath

reddy   

Posted at 3:00pm on Tuesday, April 29th, 2008

Does anybody answer here or just post Q's?

The bumbling bee   

Posted at 12:44pm on Saturday, May 10th, 2008

Hi Emma,

Can the following piece of code do?

$fileName = "ABC";

open(FILE,"

The bumbling bee   

Posted at 12:48pm on Saturday, May 10th, 2008

The bumbling bee

Hi Emma,

How do I avoid the "eating" of comments after the "<" glyph?

The bumbling bee   

Posted at 12:52pm on Saturday, May 10th, 2008

Ok, trying one more time!

$fileName = "ABC";

open(FILE,"< $fileName") or die "Could not open file $fileName";
while ($line = < FILE> ) {
$line =~ s/|+$//; ## **1 (see below)
$line =~ s/|+/ /g; ## **2 (see below)
print $line;
}
close(FILE);



## BRIEF EXPLANATION:
## ------------------
## The command "s/+++/***/" substitute "+++" with "***".
## The "|+" is regular expression matching one or more
## consecutive "|" chars.
##
##
## EXPLANATION OF "**1":
## The regular expression "|+$" requires one or more
## consecutive "|" chars at the end of the line since
## "$" match end-of-line. This is replaced by nothing.
##
## EXPLANATION OF "**2":
## The regular expression "|+$" requires one or more
## consecutive "|" as before. This is replaced by a
## single space.
## The option "g" (global) in the end indicates, that
## several sequences may be replaced if such exist.
##

beta32c   

Posted at 12:22am on Thursday, May 15th, 2008

Can we open files which are more than 2gb in size. Im not able to open my files for processing which are more than 2gb.. any ways.. reply back.

kumar   

Posted at 8:50am on Tuesday, May 20th, 2008

I have a file which the format is ".dat". I would like to read the information from this file and convert all the information to txt format. Is the perl able to do this.

Joe   

Posted at 6:51am on Friday, May 30th, 2008

what drives me nuts about many perl people offering suggestions is they offer squat. Try using this,try using that. For newbies this is no help at all. Explain it or don't bother offering suggestions. I keep seeing tons of people posting things like try this in your code. Suppose the person asking doesn't even know how to begin let alone put the code in the proper place in the script. Suppose the person has spent hours trying to figure it out and just wants some help and needs the entire script. Get real posters. I'm fed up with those who don't post the complete solution.

Newbies - start here   

Posted at 9:56am on Friday, June 13th, 2008

A lot of you are asking questions that are hard to answer if you don't know hardly anything about perl. Teach yourself the basics here: http://www.pageresource.com/cgirec/index2.htm. Or search google for beginning perl tutorial. There are many books as well. To try to help some of you, here is a full working script that will read a file in, process the file and save it to a new file. The files will be in the same folder as the perl script. This will overwrite your output file each time you run it.

#!/usr/bin/perl -w
use strict;

my $infile = 'in.txt'; # name of the file you are reading - must be in same folder as script
my $outfile = 'out.txt'; # name of file that will be created for output

open (FILEHANDLE, '' will create the file if necessary
# WARNING: this will overwrite your $outfile if it exists - copy to new file if you want to save what you have in your output file
print OUT $outdata; # write the data - will overwrite whatever you had in the output file previously
close OUT; # close the file

exit; # you are done

Anonymous   

Posted at 10:14am on Friday, June 13th, 2008

OK. One last try with the HTML characters escaped. (In fact, I escaped the characters, like <> using my script below)

A lot of you are asking questions that are hard to answer if you don't know hardly anything about perl. Teach yourself the basics here: http://www.pageresource.com/cgirec/index2.htm. Or search google for beginning perl tutorial. There are many books as well. To try to help some of you, here is a full working script that will read a file in, process the file and save it to a new file. The files will be in the same folder as the perl script. This will overwrite your output file each time you run it.

#!/usr/bin/perl -w
use strict;

my $infile = 'in.txt'; # name of the file you are reading - must be in same folder as script
my $outfile = 'out.txt'; # name of file that will be created for output

open (FILEHANDLE, '<', $infile); # this makes the file ready for reading from FILEHANDLE
# '<' means read only

my @inlines; # this is an array. An array holds a list of items. Each list item will be 1 line from the input file
@inlines = <FILEHANDLE>; # this reads the input file into the array - each array item holds 1 line of the file
my @outlines; # we will put the output lines here

#we're done reading the file - close it
close FILEHANDLE;

foreach my $line (@inlines) { # this cycles through the input file info 1 line at a time

chomp($line); # remove newline character at end of line

# I will show a few examples of what you can do to process each line
# just uncomment the code (remove the # in front of the code) to use what you want

# # change all '|' characters to tabs
# $line =~ s/\|/\t/g;

# # separate each word - one word per line - changes whitespace (spaces, tabs, etc) to new lines
# $line =~ s/\s+/\n/g;

# # replace the line with new content
# $line = "Goodbye my friend." if ($line =~ /^Hello everyone!$/); # if the line said 'Hello everyone!', now it will say 'Goodbye my friend.'

# # replace a word with another
# my $search_word = 'aks';
# my $replace_word = 'ask';
# $line =~ s/$search_word/$replace_word/gi; # g replaces all occurances, i makes it case insesitive - matches lower case and upper case

# url encode the line to make it safe for posting, so that < characters won't mess it up (such as for the comments at http://www.perlfect.com/articles/perlfile.shtml)
# $line =~ s/([^A-Za-z0-9])/sprintf("%%%02X", ord($1))/seg;

#escape HTML Characters "<", ">", "&" etc.
$line =~ s/([^\w\s])/sprintf ("&#%d;", ord ($1))/ge;

# put the line in the output array
push(@outlines,$line);
}

# join the output lines into one variable with a newline character between each line
my $outdata = join("\n",@outlines);

# save $outdata to the $outfile
open (OUT,">", $outfile); # this will open the $outfile for writing, and '>' will create the file if necessary
# WARNING: this will overwrite your $outfile if it exists - copy to new file if you want to save what you have in your output file
print OUT $outdata; # write the data - will overwrite whatever you had in the output file previously
close OUT; # close the file

exit; # you are done

hiru..   

Posted at 2:38am on Wednesday, June 18th, 2008

i want to write an array into a textfile. i m using active perl in windows xp....

noor   

Posted at 11:57pm on Wednesday, June 18th, 2008

how to delete a portion or couple lines from the file basically text file

Anonymous   

Posted at 5:05am on Thursday, July 3rd, 2008

i have one already open file . please tell how to delete the 4 th line . again i needto addd differnt data to fil

Barney   

Posted at 2:58pm on Friday, July 4th, 2008

I want to manually process many text files as follows:

myscript.pl file1.txt
myscript.pl differentfilename.txt

I am able to read the file into an array as follows:
my @INFILE = ;

But I don't know how to get the filenames to uniquely assign output files (ie. file1_out.txt, differentfilename_out.txt)

Thanks in advance.

Ravindra   

Posted at 4:31am on Tuesday, July 15th, 2008

MY task is to read a file from verilog and have to listout the input and output in readed file to the screen?Pls help me out today i have to submit it

jaichaud   

Posted at 7:10am on Wednesday, July 16th, 2008

Ravindra - can you give a few more details about how the data file is structured - maybe even a small snippet? Without knowing the data file layout, it's hard to offer any code.

milli   

Posted at 10:01am on Friday, July 18th, 2008

hi i need to open a file WICH I GOT THE NAME OF THE FILE FROM THE USER and to find how many times a specific word apeared (eg APPLE) and change apart of the word to something else(eg from APPLE to APACH), CAN U HELP ME...

M@ Hardcastle   

Posted at 3:51pm on Thursday, July 24th, 2008

my ($filename) = @ARGV;
open my($filehand), $filename;
my $file = join '', <$filehand>;
$file =~ s/(?!bAP)PLE(?=(?:b.))/ACH/g;
print $file;

Example
--------
apple.pl apple.txt > apple.txt

vaskar deka   

Posted at 2:38am on Saturday, July 26th, 2008

i need to read a file character by character using array through perl

cory   

Posted at 9:07am on Friday, August 1st, 2008

Hello, sorry to post another question but I just encountered a new problem with file writing that I never have before. I've been using this logger function on many of my scripts and it has been working just fine:

sub logger()
{
if($#_ == "-1")
{
print "Error: logger requires a logfile pathnamen";
return 0;
}

my $logfilename=shift(@_);
my $message;

if($#_ == "-1")
{
$message="";
}

else
{
$message=shift(@_);
}

my $tmplog = new IO::File;
$tmplog->open("+>>$logfilename") or die("Can't open $logfilenamen");
$tmplog->print("$messagen");
$tmplog->close;
return 1;
}

In my new script, the function will log only a couple lines of data and nothing else past that, even though sometimes the file does in fact get larger. I have the permissions set fine, and I've been trying every different form of file handling, file locking, file permissions,file caching etc. HOWEVER, some of the scripts functions are able to print more than one line, but when I issue the following, only "type" prints out:

logger("$masterlog","Type: $mode{$sys}{$type}");
logger("$masterlog","Hostname: $hostname{$sys}{eth0}");

I've even redefined $masterlog before every call, still nothing. Can anyone help me?!? Thanks so much.

cory   

Posted at 9:09am on Friday, August 1st, 2008

Sorry, that comment got skewed a little. Corrections:
$tmplog->print("$messagen");
$tmplog->open("+>>$logfilename") or die("Can't open $logfilename");

Lee   

Posted at 8:38pm on Saturday, August 16th, 2008

Hi there,
i got a question about inputing data from a .txt file and using the data in a perl script (.pl) , can someone tell me what i need to type in the command line thanks.

Cool Dude   

Posted at 11:44pm on Sunday, August 17th, 2008

Hi, need help.

Env: Windows
Ver: 5.10

I want get the status, if the file is in use [even if by notepad].
My requirement is I want to skip the files in the directory which are not in use.

Friends any suggestions?

Todd L   

Posted at 2:48am on Thursday, August 21st, 2008

Hi!

I am using Perl v5.8.8 on a MS Win32-x86 system (XP Prof SP2).
I am trying to read a *.doc file(STDIN) & split it into multiple files based on the split pattern "* * * * * AREA"
The criteria is to use the split function & to get the following outcome:

the * * * * * AREA 1 line & above lines & written to an output file e.g. AREA1.out,
the * * * * * AREA2 line & above lines up to(not including * * * * * AREA 1 line written to an output file eg. AREA2.out & so on up to AREA 40.


aaaaa
bbbbb AREA1.out
ccccc
ddddd
* * * * * AREA 1

eeeee
eeeee
ffffffffff
fffffffff AREA2.out
gggg
gggg
* * * * * AREA 2
....
....
....
....
* * * * * AREA 40

Looking at other forums & threads I’ve come across similar code requests (below 1 is a Unix-based solution).
http://www.unix.com/shell-programming-scripting/14576-split-file-using-awk.html

Your advice & help is appreciated.

Thanks Todd

Kopu   

Posted at 7:12am on Tuesday, August 26th, 2008

Todd L ... i'll give you an example for one file - you'll make it for several :)

my $filename = 'input.doc'; #this is your file name
my $splitpatt = '*******\n'; #you must know your pattern
open FH, "$filename";
print FH $file[$_];
close FH;
}


this is simplied idea i've got ... i did not check it if it work ... but the idea is clear :) i hope ...
call me at kopu.bg@gmail.com if you need some more ... :)

Kopu   

Posted at 7:17am on Tuesday, August 26th, 2008

damn this cutting things ...
Todd L ... i'll give you an example for one file - you'll make it for several :)

my $filename = 'input.doc'; #this is your file name
my $splitpatt = '*******\n'; #you must know your pattern
open FH, "$filename";
print FH $file[$_];
close FH;
}

Anonymous   

Posted at 7:20am on Tuesday, August 26th, 2008

Grrrrrrrrrrrrr ...

my $filename = 'input.doc'; #this is your file name
my $splitpatt = '*******\n'; #you must know your pattern
open FH, "\$filename";
print FH $file[$_];
close FH;
}

Kopu   

Posted at 7:22am on Tuesday, August 26th, 2008

i give up ... Todd ... write one email ... i'll send you the script ... than if you can - post it here ... i give up ...

Todd L   

Posted at 3:35pm on Tuesday, August 26th, 2008

Hi Kopu,
Thanks for your reply.I've emailed you there.
Todd

NewToPerl   

Posted at 6:15pm on Tuesday, August 26th, 2008

Hi,
I have two scripts say t1 and t2. "t1" is printing some lines and "t2" is reading from STDIN. I need to run only t1 and pass all the output to STDIN of t2. I tried with pipe, fork-exec combination in t1 but does not seem to work. Is there any easier way to do this? Effectively i need to achieve the functionality of "./t1 | ./t2" by running only t1 script.
Thanks for your help

omar   

Posted at 12:55am on Thursday, August 28th, 2008

hello guys i need help please in perl i have this program if any body can do it for me i will appreciate it a lot for him this is the program:
• A log of internet downloads is kept and bills are issued once a month.
• The log has the following structure:

userID;MBDowloaded

• Your task is to write an algorithm that analyses the log and creates a bill for each userID.
• To produce the bill, you will need to look up the name and credit card number of each user from a hash table provided.
• An input file is included in the assignment files - assignment1.txt
• When you run your script, take the name of the file from the command line.
• If the command line parameter is missing, prompt the user for the file name to use and keep prompting until they enter something.
• If the file cannot be found (assume it is in the current directory, that is the same place the script is running from) then display a message and finish immediately with a “die”.
• Read the file and ensure the records you read from the log have the correct userID structure: uppercase ST or TE followed by 4 digits only. Then the records must have a semicolon and a positive number (MBDownloaded).
• Assume there will be one record only for each userID.
• Any records that are not in this format must be copied to a new file called Errors.txt. Do not try to process them.
• For each valid log record, use the userID as the key to a hash table of personal information provided.
• The hash table has the structure of userID as the key and Name and Mastercard number separated by a colon as the value.

userID => Name:Credit card number

• Use the information from the log record and the hash table to produce a bill for each user as follows. (The bill will take the form of messages to the system console).
• Charges are 1 cent per megabyte for teachers and 0.1 cent for students.

Name : Fred Bloggs
UserID : ST1123
Mastercard number: 1234567890123457
MB downloaded: 720
Charge: $0.72

omar   

Posted at 12:55am on Thursday, August 28th, 2008

please send it to my email account : omargh84@hotmail.com

Josh   

Posted at 1:40am on Monday, September 1st, 2008

Hi, the question is simple and shows that I am a newbie.
"How to open files > 2 GB?"
I have a script that tries opening a file and if the file is > 2GB in size, it it skipping the part of code without showing any error and proceding with remaining...
What is the exact format of open() function that I need here?

karthick   

Posted at 12:33am on Tuesday, September 16th, 2008

i gotta assignment such that i have to sort the file contents of a file say data.txt and i need to create a another file data1.txt which should have the sorted contents of data.txt..can any body help.....

karthick   

Posted at 12:34am on Tuesday, September 16th, 2008

sorry the above program has to be done in perl

joe bloggs   

Posted at 4:38pm on Tuesday, September 16th, 2008

stop cheating CIT lol

karthick   

Posted at 12:43am on Friday, September 19th, 2008

What do you mean joe...........CIT????

Anuj   

Posted at 2:22am on Sunday, September 21st, 2008

How to store the contents of an aray into a file and then reading the values from that file

Please help me pout on this !!!

karthick   

Posted at 8:56pm on Sunday, September 21st, 2008

my @lines = ----nothing but a file handle
foreach $line (@lines}
{
print $line;
}
by this u wil be able to store the contents of the file in the array called @lines and you can proceed further

karthick   

Posted at 8:58pm on Sunday, September 21st, 2008

in that previous post
my @lines= ---a file handle

srinivas   

Posted at 12:10am on Monday, October 6th, 2008

Hi, i want to capture ip address & host names in a text file & put those hostnames & ipaddress to a new file. please help me out

Anonymous   

Posted at 12:12am on Monday, October 6th, 2008

eg: i have to huge lines in my text file containing host names & ip address along with other details so i want to take only ip address & host names in that file & put those into a new file. please send it to my id srinirelq@gmail.com

Hi   

Posted at 3:47pm on Thursday, October 9th, 2008

I am trying to write a perl CGI script that opens a file for writing. When I run it online however it does not recognise the path name ~ cannot find the file to write. My file is in the same folder as my cgi script.
Can someone tell me the likely problem?

Shakthi   

Posted at 8:56pm on Friday, October 10th, 2008

How to write a file in a path which has space in it Like: C:perl filefilenamefile.txt

Shakthi   

Posted at 8:58pm on Friday, October 10th, 2008

How to write a file in a path which has space in it Like: C://perl file//filename//file.txt

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