This is my script count.pl, I am trying to count the number of lines in a file.
The script's code :
chdir $filepath;
if (-e "$filepath"){
$total = `wc -l < file.list`;
printf "there are $total number of lines in file.list";
}
i can get a correct output, but i do not want to count blank lines and anything in the file that start with #. any idea ?
As this is a Perl program already open the file and read it, filtering out lines that don't count with
open my $fh, '<', $filename or die "Can't open $filename: $!";
my $num_lines = grep { not /^$|^\s*#/ } <$fh>;
where $filename is "file.list." If by "blank lines" you mean also lines with spaces only then chagne regex to /^\s*$|^\s*#/. See grep, and perlretut for regex used in its condition.
That filehandle $fh gets closed when the control exits the current scope, or add close $fh; after the file isn't needed for processing any more. Or, wrap it in a block with do
my $num_lines = do {
open my $fh, '<', $filename or die "Can't open $filename: $!";
grep { not /^$|^\s*#/ } <$fh>;
};
This makes sense doing if the sole purpose of opening that file is counting lines.
Another thing though: an operation like chdir should always be checked, and then there is no need for the race-sensitive if (-e $filepath) either. Altogether
# Perhaps save the old cwd first so to be able to return to it later
#my $old_cwd = Cwd::cwd;
chdir $filepath or die "Can't chdir to $filepath: $!";
open my $fh, '<', $filename or die "Can't open $filename: $!";
my $num_lines = grep { not /^$|^\s*#/ } <$fh>;
A couple of other notes:
There is no reason for printf. For all normal prints use say, for which you need use feature qw(say); at the beginning of the program. See feature pragma
Just in case, allow me to add: every program must have at the beginning
use warnings;
use strict;
Perhaps the original intent of the code in the question is to allow a program to try a non-existing location, and not die? In any case, one way to keep the -e test, as asked for
#my $old_cwd = Cwd::cwd;
chdir $filepath or warn "Can't chdir to $filepath: $!";
my $num_lines;
if (-e $filepath) {
open my $fh, '<', $filename or die "Can't open $filename: $!";
$num_lines = grep { not /^$|^\s*#/ } <$fh>;
}
where I still added a warning if chdir fails. Remove that if you really don't want it. I also added a declaration of the variable that is assigned the number of lines, with my $total_lines;. If it is declared earlier in your real code then of course remove that line here.
perl -ne '$n++ unless /^$|^#/ or eof; print "$n\n" if eof'
Works with multiple files too.
perl -ne '$n++ unless /^$|^#/ or eof; END {print "$n\n"}'
Better for a single file.
open(my $fh, '<', $filename);
my $n = 0;
for(<$fh>) { $n++ unless /^$|^#/}
print $n;
Using sed to filter out the "unwanted" lines in a single file:
sed '/^\s*#/d;/^\s*$/d' infile | wc -l
Obviously, you can also replace infile with a list of files.
The solution is very simple, no any magic.
use strict;
use warnings;
use feature 'say';
my $count = 0;
while( <> ) {
$count++ unless /^\s*$|^\s*#/;
}
say "Total $count lines";
Reference:
<>
Related
I am writing a script in perl where I am creating a file and getting input from user for file but when I am copying that file to other location the file is copying but it is empty only. My code is
# !/usr/bin/perl -w
for($i = 1;$i<5;$i++)
{
open(file1,"</u/man/fr$i.txt");
print "Enter text for file $i";
$txt = <STDIN>;
print file1 $txt;
open(file2,">/u/man/result/fr$i.txt");
while(<file1>)
{
print file2 $_;
}
close(file1);
close(file2);
}
fr1 to fr4 are creating but these are empty. like when I run my code it is asking for input i provide the input and code run without error but still the files are empty. Please help.
in line number 4 I changed < to > also as I thought for creating new file it might need that but still it is not working
You need to close the filehandle that was written to in order to be able to read from that file.
use warnings;
use strict;
use feature 'say';
for my $i (1..4)
{
my $file = "file_$i.txt";
open my $fh, '>', $file or die "Can't open $file: $!";
say $fh "Written to $file";
# Opening the same filehandle first *closes* it if already open
open $fh, '<', $file or die "Can't open $file: $!";
my $copy = "copy_$i.txt";
open my $fh_cp, '>', $copy or die "Can't open $copy: $!";
while (<$fh>) {
print $fh_cp $_;
}
close $fh_cp; # in case of early errors in later iterations
close $fh;
}
This creates the four files, file_1.txt etc, and their copies, copy_1.txt etc.
Please note the compulsory checking whether open worked.
You can't write to a filehandle that's not open for writing. You can't read from a filehandle that's not open for reading. Never ignore the return value of open.
# !/usr/bin/perl
use warnings; # Be warned about mistakes.
use strict; # Prohibit stupid things.
for my $i (1 .. 4) { # lexical variable, range
open my $FH1, '>', "/u/man/fr$i.txt" # 3 argument open, lexical filehandle, open for writing
or die "$i: $!"; # Checking the return value of open
print "Enter text for file $i: ";
my $txt = <STDIN>;
print {$FH1} $txt;
open my $FH2, '<', "/u/man/fr$i.txt" # Reopen for reading.
or die "$i: $!";
open my $FH3, '>', "/u/man/result/fr$i.txt" or die "$i: $!";
while (<$FH2>) {
print {$FH3} $_;
}
close $FH3;
}
I opened the file in write mode using filehandler1 Then i again opened the file in read mode using same filehandler1 then I opened filehandler2 for destiantion So it is working fine for me then.
system("cp myfile1.txt /somedir/myfile2.txt")
`cp myfile1.txt /somedir/myfile2.txt`
Trying to write a script which opens a directory and reads bunch of multiple log files line by line and search for information such as example:
"Attendance = 0 " previously I have used grep "Attendance =" * to search my information but trying to write a script to search for my information.
Need your help to finish this task.
#!/usr/bin/perl
use strict;
use warnings;
my $dir = '/path/';
opendir (DIR, $dir) or die $!;
while (my $file = readdir(DIR))
{
print "$file\n";
}
closedir(DIR);
exit 0;
What's your perl experience?
I'm assuming each file is a text file. I'll give you a hint. Try to figure out where to put this code.
# Now to open and read a text file.
my $fn='file.log';
# $! is a variable which holds a possible error msg.
open(my $INFILE, '<', $fn) or die "ERROR: could not open $fn. $!";
my #filearr=<$INFILE>; # Read the whole file into an array.
close($INFILE);
# Now look in #filearr, which has one entry per line of the original file.
exit; # Normal exit
I prefer to use File::Find::Rule for things like this. It preserves path information, and it's easy to use. Here's an example that does what you want.
use strict;
use warnings;
use File::Find::Rule;
my $dir = '/path/';
my $type = '*';
my #files = File::Find::Rule->file()
->name($type)
->in(($dir));
for my $file (#files){
print "$file\n\n";
open my $fh, '<', $file or die "can't open $file: $!";
while (my $line = <$fh>){
if ($line =~ /Attendance =/){
print $line;
}
}
}
My program is trying to search a string from multiple files in a directory. The code searches for single patterns like perl but fails to search a long string like Status Code 1.
Can you please let me know how to search for strings with multiple words?
#!/usr/bin/perl
my #list = `find /home/ad -type f -mtime -1`;
# printf("Lsit is $list[1]\n");
foreach (#list) {
# print("Now is : $_");
open(FILE, $_);
$_ = <FILE>;
close(FILE);
unless ($_ =~ /perl/) { # works, but fails to find string "Status Code 1"
print "found\n";
my $filename = 'report.txt';
open(my $fh, '>>', $filename) or die "Could not open file '$filename' $!";
say $fh "My first report generated by perl";
close $fh;
} # end unless
} # end For
There are a number of problems with your code
You must always use strict and use warnings at the top of every Perl program. There is little point in delcaring anything with my without strict in place
The lines returned by the find command will have a newline at the end which must be removed before Perl can find the files
You should use lexical file handles (my $fh instead of FILE) and the three-parameter form of open as you do with your output file
$_ = <FILE> reads only the first line of the file into $_
unless ($_ =~ /perl/) is inverted logic, and there's no need to specify $_ as it is the default. You should write if ( /perl/ )
You can't use say unless you have use feature 'say' at the top of your program (or use 5.010, which adds all features available in Perl v5.10)
It is also best to avoid using shell commands as Perl is more than able to do anything that you can using command line utilities. In this case -f $file is a test that returns true if the file is a plain file, and -M $file returns the (floating point) number of days since the file's modification time
This is how I would write your program
#!/usr/bin/perl
use strict;
use warnings;
use 5.010;
for my $file ( glob '/home/ad/*' ) {
next unless -f $file and int(-M $file) == 1;
open my $fh, '<', $file or die $!;
while ( <$fh> ) {
if ( /perl/ ) {
print "found\n";
my $filename = 'report.txt';
open my $out_fh, '>>', $filename or die "Could not open file '$filename': $!";
say $fh "My first report generated by perl";
close $out_fh;
last;
}
}
}
it should have matched unless $_ contains text in different case.
try this.
unless($_ =~ /Status\s+Code\s+1/i) {
Change
unless ($_ =~ /perl/) {
to:
unless ($_ =~ /(Status Code 1)/) {
I am certain the above works, except it's case sensitive.
Since you question it, I rewrote your script to make more sense of what you're trying to accomplish and implement the above suggestion. Correct me if I am wrong, but you're trying to make a script which matches "Status Code 1" in a bunch of files where last modified within 1 day and print the filename to a text file.
Anyways, below is what I recommend:
#!/usr/bin/perl
use strict;
use warnings;
my $output_file = 'report.txt';
my #list = `find /home/ad -type f -mtime -1`;
foreach my $filename (#list) {
print "PROCESSING: $filename";
open (INCOMING, "<$filename") || die "FATAL: Could not open '$filename' $!";
foreach my $line (<INCOMING>) {
if ($line =~ /(Status Code 1)/) {
open( FILE, ">>$output_file") or die "FATAL: Could not open '$output_file' $!";
print FILE sprintf ("%s\n", $filename);
close(FILE) || die "FATAL: Could not CLOSE '$output_file' $!";
# Bail when we get the first match
last;
}
}
close(INCOMING) || die "FATAL: Could not close '$filename' $!";
}
Alright, so I'm back with another question. I know in Python there is a way to read in a file without specifying which file it will be, until you are in the command prompt. So basically you can set the script up so that you can read in any file you want and don't have to go back and change the coding every time. Is there a way to do this in Perl? If so, can you write files like that too? Thanks.
This is what I have:
open (LOGFILE, "UNSUCCESSFULOUTPUT.txt") or die "Can't find file";
open FILE, ">", "output.txt" or die $!;
while(<LOGFILE>){
print FILE "ERROR in line $.\n" if (/Error/);
}
close FILE;
close LOGFILE;
This is what I have nome:
#!/usr/local/bin/perl
my $argument1 = $ARGV[0];
open (LOGFILE, "<$argument1") or die "Can't find file";
open FILE, ">>output.txt" or die $!;
while(<LOGFILE>){
print FILE "ERROR in line $.\n" if (/Error/);
}
close FILE;
close LOGFILE;
And it's still not appending...
Command line arguments are provided in #ARGV. You can do as you please with them, including passing them as file names to open.
my ($in_qfn, $out_qfn) = #ARGV;
open(my $in_fh, '<', $in_qfn ) or die $!;
open(my $out_fh, '>', $out_qfn) or die $!;
print $out_fh $_ while <$in_fh>;
But that's not a very unixy way of doing things. In unix tradition, the following will read from every file specified on the command line, one line at a time:
while (<>) {
...
}
Output is usually placed in files through redirection.
#!/usr/bin/env perl
# This is mycat.pl
print while <>;
# Example usage.
mycat.pl foo bar > baz
# Edit foo in-place.
perl -i mycat.pl foo
The only time one usually touches #ARGV is to process options, and even then, one usually uses Getopt::Long instead of touching #ARGV directly.
Regarding your code, your script should be:
#!/usr/bin/env perl
while (<>) {
print "ERROR in line $.\n" if /Error/;
}
Usage:
perl script.pl UNSUCCESSFULOUTPUT.txt >output.txt
You can get rid of perl from the command if you make script.pl executable (chmod u+x script.pl).
This is what I believe you want:
#!usr/bin/perl
my $argument1 = $ARGV[0];
open (LOGFILE, "<$argument1") or die "Can't find file";
open (FILE, ">output.txt") or die $!;
while(<LOGFILE>){
print FILE "ERROR in line $.\n" if (/Error/);
}
close FILE;
close LOGFILE;
Ran as from the command line:
> perl nameofpl.pl mytxt.txt
For appending change this line:
open (FILE, ">output.txt") or die $!;
To the remarkably similar:
open (FILE, ">>output.txt") or die $!;
I assume you are asking how to pass an argument to a perl script. This is done with the #ARGV variable.
use strict;
use warnings;
my $file = shift; # implicitly shifts from #ARGV
print "The file is: $file\n";
You can also make use of the magic of the diamond operator <>, which will open the arguments to the script as files, or use STDIN if no arguments are supplied. The diamond operator is used as a normal file handle, typically while (<>) ...
ETA:
With the code you supplied, you can make it more flexible by doing this:
use strict;
use warnings; # always use these
my $file = shift; # first argument, required
my $outfile = shift // "output.txt"; # second argument, optional
open my $log, "<", $file or die $!;
open my $out, ">", $outfile or die $!;
while (<$log>) {
print $out "ERROR in line $.\n" if (/Error/);
}
Also see ikegami's answer on how to make it more like other unix tools, e.g. accept STDIN or file arguments, and print to STDOUT.
As I commented in your earlier question, you may simply wish to use an already existing tool for the job:
grep -n Error input.txt > output.txt
I want to remove all lines in a text file that start with HPL_ I have acheived this and can print to screen, but when I try to write to a file, I just get the last line of the amended text printed in the new file. Any help please!
open(FILE,"<myfile.txt");
#LINES = <FILE>;
close(FILE);
open(FILE,">myfile.txt");
foreach $LINE (#LINES) {
#array = split(/\:/,$LINE);
my $file = "changed";
open OUTFILE, ">$file" or die "unable to open $file $!";
print OUTFILE $LINE unless ($array[0] eq "HPL_");
}
close(FILE);
close (OUTFILE);
exit;
You just want to remove all lines that start with HPL_? That's easy!
perl -pi -e 's/^HPL_.*//s' myfile.txt
Yes, it really is just a one-liner. :-)
If you don't want to use the one-liner, re-write the "write to file" portion as follows:
my $file = "changed";
open( my $outfh, '>', $file ) or die "Could not open file $file: $!\n";
foreach my $LINE (#LINES) {
my #array = split(/:/,$LINE);
next if $array[0] eq 'HPL_';
print $outfh $LINE;
}
close( $outfh );
Note how you are open()ing the file each time through the loop. This is causing the file to only contain the last line, as using open() with > means "overwrite what's in the file". That's the major problem with your code as it stands.
Edit: As an aside, you want to clean up your code. Use lexical filehandles as I've shown. Always add the three lines that tchrist posted at the top of every one of your Perl programs. Use the three-operator version of open(). Don't slurp the entire file into an array, as if you try to read a huge file it could cause your computer to run out of memory. Your program could be re-written as:
#!perl
use strict;
use autodie;
use warnings FATAL => "all";
my $infile = "myfile.txt";
my $outfile = "changed.txt";
open( my $infh, '<', $infile );
open( my $outfh, '>', $outfile );
while( my $line = <$infh> ) {
next if $line =~ /^HPL_/;
print $outfh $line;
}
close( $outfh );
close( $infh );
Note how with use autodie you don't need to add or die ... to the open() function, as the autodie pragma handles that for you.
The issue with your code is that you open the file for output within your line-processing loop which, due to your use of the '>' form of open, opens the file each time for write, obliterating any previous content.
Move the invocation of open() to the top of your file, above the loop, and it should work.
Also, I'm not sure of your intent but at line 4 of your example, you reopen your input file for write (using '>'), which also clobbers anything it contains.
As a side note, you might try reading up on Perl's grep() command which is designed to do exactly what you need, as in:
#!/usr/bin/perl
use strict;
use warnings;
open(my $in, '<', 'myfile.txt') or die "failed to open input for read: $!";
my #lines = <$in> or die 'no lines to read from input';
close($in);
# collect all lines that do not begin with HPL_ into #result
my #result = grep ! /^HPL_/, #lines;
open(my $out, '>', 'changed.txt') or die "failed to open output for write: $!";
print { $out } #result;
close($out);