Perl file read write

open(DATA,"+>>file.txt") || die "Couldn't open file file.txt, $!";

close(DATA) || die "Couldn't close file properly";

< or r      Read Only Access
> or w      Creates, Writes, and Truncates
>> or a     Writes, Appends, and Creates
+< or r+    Reads and Writes
+> or w+    Reads, Writes, Creates, and Truncates
+>> or a+   Reads, Writes, Appends, and Creates


Almost the same except it uses the system open() (instead of perl open?)

sysopen(DATA, "file.txt", O_RDWR|O_TRUNC );

O_RDWR      Read and Write
O_RDONLY    Read Only
O_WRONLY    Write Only
O_CREAT     Create the file
O_APPEND    Append the file
O_TRUNC     Truncate the file
O_EXCL      Stops if file already exists
O_NONBLOCK  Non-Blocking usability

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#!/usr/bin/perl

# get a file as an array
open(DATA,"<import.txt") or die "Can't open data";
@lines = <DATA>;
close(DATA);

unlink ("/usr/test/file1.txt");  # delete a file
rename ("/usr/test/file1.txt", "/usr/test/file2.txt" );

# get character
getc FILEHANDLE

# read a block of data
read FILEHANDLE, SCALAR, LENGTH, OFFSET


use File::Copy;
    copy("file1","file2") or die "Copy failed: $!";
    copy("Copy.pm",\*STDOUT);
    move("/dev1/fileA","/dev2/fileB");
    use File::Copy "cp";
    $n = FileHandle->new("/a/file","r");
    cp($n,"x");


#!/usr/bin/perl

# Open file to read
open(DATA1, "<file1.txt");

# Open new file to write
open(DATA2, ">file2.txt");

# Copy data from one file to another.
while(<DATA1>)
{
   print DATA2 $_;
}
close( DATA1 );
close( DATA2 );


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tell FILEHANDLE  # returns the position of the file pointer, in bytes
seek FILEHANDLE, POSITION, WHENCE   # whence is either start (0) , end, or current

my (@description,$size);
if (-e $file)
{
   push @description, 'binary' if (-B _);
   push @description, 'a socket' if (-S _);
   push @description, 'a text file' if (-T _);
   push @description, 'a block special file' if (-b _);
   push @description, 'a character special file' if (-c _);
   push @description, 'a directory' if (-d _);
   push @description, 'executable' if (-x _);
   push @description, (($size = -s _)) ? "$size bytes" : 'empty';
   print "$file is ", join(', ',@description),"\n";
}


-A  Age of file (at script startup) in days since modification.
-B  Is it a binary file?
-C  Age of file (at script startup) in days since modification.
-M  Age of file (at script startup) in days since modification.
-O  Is the file owned by the real user ID?
-R  Is the file readable by the real user ID or real group?
-S  Is the file a socket?
-T  Is it a text file?
-W  Is the file writable by the real user ID or real group?
-X  Is the file executable by the real user ID or real group?
-b  Is it a block special file?
-c  Is it a character special file?
-d  Is the file a directory?
-e  Does the file exist?
-f  Is it a plain file?
-g  Does the file have the setgid bit set?
-k  Does the file have the sticky bit set?
-l  Is the file a symbolic link?
-o  Is the file owned by the effective user ID?
-p  Is the file a named pipe?
-r  Is the file readable by the effective user or group ID?
-s  Returns the size of the file, zero size = empty file. 
-t  Is the filehandle opened by a TTY (terminal)?
-u  Does the file have the setuid bit set?
-w  Is the file writable by the effective user or group ID?
-x  Is the file executable by the effective user or group ID?
-z  Is the file size zero?


opendir DIRHANDLE, EXPR  # To open a directory
readdir DIRHANDLE        # To read a directory
rewinddir DIRHANDLE      # Positioning pointer to the begining
telldir DIRHANDLE        # Returns current position of the dir
seekdir DIRHANDLE, POS   # Pointing pointer to POS inside dir
closedir DIRHANDLE       # Closing a directory.

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Extract from a file into an array only lines containing "app.service1." , pass array to sub by reference


#!/usr/bin/perl
use Switch;
use strict;

use constant SERVICEHEADER1 => "app.service1.";

my @filedata = fileToArray( "/var/lib/tomcat6/webapps/authgateway/WEB-INF/app.properties" );
my @service1 = getServiceConfiguration( \@filedata , SERVICEHEADER1 );
printArray( \@service1 );


sub fileToArray( ;$ )
{
  my $data_file = $_[0];
  open( DATA , "$data_file" ) or die "can't open $data_file \n";
  my @array_of_data = <DATA>;
  close( DATA );
  return @array_of_data;
}

sub getServiceConfiguration()
{
  my( $ref_filedata, $servicenumber) = @_;
  my @result;

  foreach my $line ( @{$ref_filedata} )
  {
    my $match = $line =~ m/$servicenumber/ ;
    if( $match )
    {
      push( @result , $line );
    }
  }
  return @result;
}

sub printArray()
{
  my( $ref_array ) = @_;
  foreach my $value ( @{$ref_array} )
  {
    print $value;
  }
}