Perl Programming - 03 Programming File
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03-Perl Programming File 134 Danairat T. Line ID: Danairat FB: Danairat Thanabodithammachari +668-1559-1446
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Transcript of 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/perluse strict;use warnings;
my $myFile = "fileread.txt"; # the file “filetest.txt” must be existmy $myLine;if (open (MYFILEHANDLE, $myFile)) {
while ($myLine = <MYFILEHANDLE>) { # read linechomp($myLine); # trim whitespace at end of lineprint "$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/perluse strict;use warnings;
my $myFile = "fileread.txt"; # the file “filetest.txt” must be existmy $myLine;if (open (MYFILEHANDLE, '<' , $myFile)) { # using ‘<‘ and . for file read
while ($myLine = <MYFILEHANDLE>) { # read linechomp($myLine); # trim whitespace at end of lineprint "$myLine \n";
}close (MYFILEHANDLE);
} else {print "File could not be opened. \n";
}exit(0);
OpenFileReadEx01.pl
Results:-
<print the file content>
Danairat T.
Open File Options
140
• Using > for file writing to new file.
#!/usr/bin/perluse 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}close (MYFILEHANDLE);
} else {print "File could not be opened. \n";
}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/perluse 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}close (MYFILEHANDLE);
} else {print "File could not be opened. \n";
}exit(0);
OpenFileAppendEx01.pl
Results:-
<see from the output file>
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/perluse strict;use warnings;use Fcntl;
my $file = 'testfile.txt';
# open the fileopen (FILE, ">>", "$file") || die "problem opening $file\n";
# immediately lock the fileflock (FILE, 2);
# test keeping the lock on the file for ~20 secondsmy $count = 0;while ($count++ < 30){print "count = $count\n";print FILE "count = $count\n";sleep 1;}
# close the file, which also removes the lockclose (FILE);
exit(0);
FileExLockEx01.pl
Please run this concurrence
with FileExLockEx02.pl, see
next page.
Results:-
<see from the output file>
Danairat T.
File Locking – Exclusive Locking
144
#!/usr/bin/perluse strict;use warnings;use Fcntl;
my $file = 'testfile.txt';
# open the fileopen (FILE, ">>", "$file") || die "problem opening $file\n";
# immediately lock the fileflock (FILE, 2);
# test keeping the lock on the file for ~20 secondsmy $count = 0;while ($count++ < 30){print "count : $count\n";print FILE "count : $count\n";sleep 1;}
# close the file, which also removes the lockclose (FILE);
exit(0);
FileExLockEx02.pl
Please run this concurrency
with FileExLockEx01.pl
Results:-
<see from the output file>
Danairat T.
File Locking – Shared Locking
145
#!/usr/bin/perluse strict;use warnings;use Fcntl;
my $file = 'testfile.txt';
# open the fileopen (FILE, "<", "$file") || die "problem opening $file\n";
# immediately lock the fileflock (FILE, 1);
# test keeping the lock on the file for ~20 secondsmy $count = 0;while ($count++ < 30){
print "Shared Locking\n";sleep 1;}
# close the file, which also removes the lockclose (FILE);
exit(0);
FileShLockEx01.pl
Please run this concurrency
with FileExLockEx02.pl
Results:-
<see from the output file>
Danairat T.
Filehandle Examples
146
• Read file and write to another file
#!/usr/bin/perluse strict;use warnings;
my $myFileRead = "fileread.txt"; my $myFileWrite = "filewrite.txt";
if (open (MYFILEREAD, '<' , $myFileRead)) { # using ‘<‘ and . for file readif (open (MYFILEWRITE, '>' , $myFileWrite)) {
while (my $myLine = <MYFILEREAD>) { # read linechomp($myLine); # trim whitespace at end of lineprint MYFILEWRITE "$myLine\n";
}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/perluse strict;use warnings;use File::Copy;
my $myFileRead = "fileread.txt"; my $myFileWrite = "filewrite.txt";
if (copy ($myFileRead, $myFileWrite)) {print "success copy from $myFileRead to $myFileWrite\n“;
}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/perluse strict;use warnings;
my $myPath = "./mypath/";my $myFileWrite = "filewrite.txt";
if (unlink ("$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/perluse strict;use warnings;use File::Copy;use File::Path;
my $myFileRead = "fileread.txt"; my $myPath = "./mypath/";my $myFileWrite = "filewrite.txt";exit (0) unless (mkpath($myPath));if (move ($myFileRead, "$myPath$myFileWrite")) {
print "Success move from $myFileRead to $myFileWrite\n";} 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/perluse strict;use warnings;
my $myFile = "fileread.txt"; exit (0) unless ( open (MYFILEHANDLE, '<' , $myFile) );my @myLines = <MYFILEHANDLE>;close (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/perluse strict;use warnings;
my $myFile = "fileread.txt"; 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/perluse strict;use warnings;
my $myFile = "fileread.txt"; 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=value2param3=value3
config.conf
Danairat T.
File and Regular Expression
155
• Reading the configuration file
#!/usr/bin/perluse strict;use warnings;my $myConfigFile = "config.conf";my %configHash = ();exit (0) unless ( open (MYCONFIG, '<' , $myConfigFile) );while (<MYCONFIG>) {
chomp; # no newlines/#.*//; # no commentss/^\s+//; # no leading whites/\s+$//; # no trailing whitenext 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
param3 contains value3
param1 contains value1
Danairat T.
Line ID: Danairat
FB: Danairat Thanabodithammachari
+668-1559-1446
Thank you
