Perl Programming - 03 Programming File

03- Perl Programming
File
134
Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446

Danairat T.
Perl File Processing
• Perl works with file using a filehandle which is
a named internal Perl structure that associates
a physical file with a name.
135

Danairat T.
Files Processing - Topics
• Open and Close File
• Open File Options
• Read File
• Write File
• Append File
• Filehandle Examples
– Read file and write to another file
– Copy file
– Delete file
– Rename file
– File statistic
– Regular Expression and File processing
136

Danairat T.
Open, Read and Close File
137
• The open function takes a filename and creates a filehandle.
The file will be opened for reading only by default.
#!/usr/bin/perl
use strict;
use warnings;
my $myFile = "fileread.txt"; # the file “filetest.txt” must be exist
my $myLine;
if (open (MYFILEHANDLE, $myFile)) {
while ($myLine = <MYFILEHANDLE>) { # read line
chomp($myLine); # trim whitespace at end of line
print "$myLine n";
}
close (MYFILEHANDLE);
} else {
print "File could not be opened. n";
}
exit(0);
OpenFileEx01.pl
Results:-
<print the file content>

Danairat T.
Open File Options
138
mode operand create
delete and recreate
file if file exists
read <
write > ✓ ✓
append >> ✓
read/write +<
read/write +> ✓ ✓
read/append +>> ✓

Danairat T.
Open File Options
139
• Using < for file reading.
#!/usr/bin/perl
use strict;
use warnings;
my $myFile = "fileread.txt"; # the file “filetest.txt” must be exist
my $myLine;
if (open (MYFILEHANDLE, '<' , $myFile)) { # using ‘<‘ and . for file read
while ($myLine = <MYFILEHANDLE>) { # read line
print "$myLine n";
}
} else {
}
exit(0);
OpenFileReadEx01.pl
Results:-
<print the file content>

Danairat T.
Open File Options
140
• Using > for file writing to new file.
#!/usr/bin/perl
use strict;
use warnings;
my $myFile = "filewrite.txt";
my @myData = ("line1", "line2", "line3");
if (open (MYFILEHANDLE, '>' , $myFile)) {
foreach my $myLine (@myData) {
print MYFILEHANDLE "$myLine n"; # print to filehandle
}
} else {
}
exit(0);
OpenFileWriteEx01.pl
Results:-
<see from the output file>

Danairat T.
Open File Options
141
• Using >> to append data to file. If the file does not exist then it is create a
new file.
#!/usr/bin/perl
use strict;
use warnings;
my $myFile = "filewrite.txt";
my @myData = ("line4", "line5", "line6");
if (open (MYFILEHANDLE, ‘>>' , $myFile)) {
foreach my $myLine (@myData) {
print MYFILEHANDLE "$myLine n"; # print to filehandle
}
} else {
}
exit(0);
OpenFileAppendEx01.pl
Results:-

Danairat T.
File Locking
• Lock File for Reading (shared lock): Allow other to
open the file but no one can modify the file
• Lock File for Writing (exclusive lock): NOT allow
anyone to open the file either for reading or for
writing
• Unlock file is activated when close the file
142
Shared lock: 1
Exclusive lock: 2
Unlock: 8

Danairat T.
File Locking – Exclusive Locking
143
#!/usr/bin/perl
use strict;
use warnings;
use Fcntl;
my $file = 'testfile.txt';
# open the file
open (FILE, ">>", "$file") || die "problem opening $filen";
# immediately lock the file
flock (FILE, 2);
# test keeping the lock on the file for ~20 seconds
my $count = 0;
while ($count++ < 30)
{
print "count = $countn";
print FILE "count = $countn";
sleep 1;
}
# close the file, which also removes the lock
close (FILE);
exit(0);
FileExLockEx01.pl
Please run this concurrence
with FileExLockEx02.pl, see
next page.
Results:-

Danairat T.
File Locking – Exclusive Locking
144
#!/usr/bin/perl
use strict;
use warnings;
use Fcntl;
# open the file
open (FILE, ">>", "$file") || die "problem opening $filen";
flock (FILE, 2);
my $count = 0;
{
print "count : $countn";
print FILE "count : $countn";
sleep 1;
}
close (FILE);
exit(0);
FileExLockEx02.pl
Please run this concurrency
with FileExLockEx01.pl
Results:-

Danairat T.
File Locking – Shared Locking
145
#!/usr/bin/perl
use strict;
use warnings;
use Fcntl;
# open the file
open (FILE, "<", "$file") || die "problem opening $filen";
flock (FILE, 1);
my $count = 0;
{
print "Shared Lockingn";
sleep 1;
}
close (FILE);
exit(0);
FileShLockEx01.pl
Please run this concurrency
with FileExLockEx02.pl
Results:-

Danairat T.
Filehandle Examples
146
• Read file and write to another file
#!/usr/bin/perl
use strict;
use warnings;
my $myFileRead = "fileread.txt";
my $myFileWrite = "filewrite.txt";
if (open (MYFILEREAD, '<' , $myFileRead)) { # using ‘<‘ and . for file read
if (open (MYFILEWRITE, '>' , $myFileWrite)) {
while (my $myLine = <MYFILEREAD>) { # read line
print MYFILEWRITE "$myLinen";
}
close (MYFILEWRITE);
} else {
print "File $myFileWrite could not be opened. n";
}
close (MYFILEREAD);
} else {
print "File $myFileRead could not be opened. n";
}
exit(0);
ReadFileWriteFile01.pl
Results:-
<Please see output file>

Danairat T.
Filehandle Examples
147
• Copy File using module File::Copy
#!/usr/bin/perl
use strict;
use warnings;
use File::Copy;
if (copy ($myFileRead, $myFileWrite)) {
print "success copy from $myFileRead to $myFileWriten“;
}
exit(0);
CopyEx01.pl
Results:-
success copy from fileread.txt to filewrite.txt

Danairat T.
Filehandle Examples
148
• Delete file using unlink
– unlink $file : To remove only one file
– unlink @files : To remove the files from list
– unlink <*.old> : To remove all files .old in current dir
#!/usr/bin/perl
use strict;
use warnings;
my $myPath = "./mypath/";
if (unlink ("$myPath$myFileWrite")) {
print "Success remove ${myPath}${myFileWrite}n";
} else {
print "Unsuccess remove ${myPath}${myFileWrite}n"
}
exit(0);
FileRemoveEx01.pl
Results:-
Success remove ./mypath/filewrite.txt

Danairat T.
Filehandle Examples
149
• Create directory and move with rename the file
#!/usr/bin/perl
use strict;
use warnings;
use File::Copy;
use File::Path;
my $myPath = "./mypath/";
exit (0) unless (mkpath($myPath));
if (move ($myFileRead, "$myPath$myFileWrite")) {
print "Success move from $myFileRead to $myFileWriten";
} else {
print "Unsuccess move from $myFileRead to
${myPath}${myFileWrite}n"
}
exit(0);
FileMoveEx01.pl
Results:-
Success move from fileread.txt to ./mypath/filewrite.txt

Danairat T.
Filehandle Examples
150
• Read file to array at one time
#!/usr/bin/perl
use strict;
use warnings;
my $myFile = "fileread.txt";
exit (0) unless ( open (MYFILEHANDLE, '<' , $myFile) );
my @myLines = <MYFILEHANDLE>;
foreach my ${myLine} (@myLines) {
chomp($myLine);
print $myLine . "n";
}
exit(0);
ReadFileToArrayEx01.pl
Results:-
<The fileread.txt print to screen>

Danairat T.
Test File
151
• -e is the file exists.
• -T is the file a text file
• -r is the file readable
#!/usr/bin/perl
use strict;
use warnings;
if (-r $myFile) {
print "The file is readable n";
} else {
print "File does not exist. n";
}
exit(0);
FileTestEx01.pl
Results:-
The file is readable
• -d Is the file a directory
• -w Is the file writable
• -x Is the file executable

Danairat T.
File stat()
152
• File statistic using stat();
$dev - the file system device number
$ino - inode number
$mode - mode of file
$nlink - counts number of links to file
$uid - the ID of the file's owner
$gid - the group ID of the file's owner
$rdev - the device identifier
$size - file size in bytes
$atime - last access time
$mtime - last modification time
$ctime - last change of the mode
$blksize - block size of file
$blocks - number of blocks in a file
my ($dev, $ino, $mode, $nlink, $uid, $gid, $rdev, $size, $atime, $mtime,
$ctime, $blksize, $blocks) = stat($file);

Danairat T.
File stat()
153
• File statistic using stat();
#!/usr/bin/perl
use strict;
use warnings;
if (-e $myFile) {
my ($dev, $ino, $mode, $nlink, $uid, $gid, $rdev, $size, $atime,
$mtime, $ctime, $blksize, $blocks) = stat($myFile);
print "$size is $size bytes n";
print scalar localtime($mtime) . "n";
} else {
print "File does not exist. n";
}
exit(0);
FileStatEx01.pl
Results:-
$size is 425 bytes
Tue Nov 10 21:39:07 2009

Danairat T.
File and Regular Expression
154
• Reading the configuration file
param1=value1
param2=value2
param3=value3
config.conf

Danairat T.
File and Regular Expression
155
• Reading the configuration file
#!/usr/bin/perl
use strict;
use warnings;
my $myConfigFile = "config.conf";
my %configHash = ();
exit (0) unless ( open (MYCONFIG, '<' , $myConfigFile) );
while (<MYCONFIG>) {
chomp; # no newline
s/#.*//; # no comments
s/^s+//; # no leading white
s/s+$//; # no trailing white
next unless length; # anything left?
my ($myParam, $myValue) = split(/s*=s*/, $_, 2);
$configHash{$myParam} = $myValue;
}
close (MYCONFIG);
foreach my $myKey (keys %configHash) {
print "$myKey contains $configHash{$myKey}n";
}
exit(0);
ConfigFileReadEx01.pl
Results:-
param2 contains value2

Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446
Thank you

Perl Programming - 03 Programming File

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Perl Programming - 03 Programming File