将输出打印到perl中的文件中

Question

I have been trying to find examples related to file handling, but I haven't found anything that will solve my problem.

    use strict;
    use warnings;

    my ($m, $b)    = @ARGV;
    my $count_args = $#ARGV + 1;
    my $times      = 2**$m;

    my $output = "main fucntion to be called???\n";

    open(OUTFILE, "> output1.txt") || die "could not open output file";

    print OUTFILE "$output\n"; ## Notice, there is not a comma after the file handle and the string to be output

    close(OUTFILE);

    main();

    sub main {
      if ($m =~ /^\d+$/) {
        if ($b =~ /^and$/i) {
          func_and();
        }
        else {
          print " not supported\n";
        }
      }
      else {
        print " enter valid number of pins\n";
      }
    }

    sub func_and {
      my $bit;
      for (my $i = 0 ; $i < $times ; $i++) {
        my $p = sprintf("%0${m}b", $i);
        print "$p\t";
        my @c = split('', $p);
        my $result = 100;
        foreach $bit (@c) {
          if ($result < 100) {
            $result = $result && $bit;
          }
          else {
            $result = $bit;
          }
        }
        print "result is $result \n";
      }
    }

This program prints an output if I provide the input as 2 and the output is printed on the screen.

I want to change the file handle STDOUT of this program that is i want to print the output to output1.txt file

Can you please point out the mistake I am making? ----->

copy STDOUT to another filehandle

open (my $STDOLD, '>&', STDOUT);

# redirect STDOUT to log.txt

open (STDOUT, '>>', "$ARGV[1]".".log");

print main();

# restore STDOUT
open (STDOUT, '>&', $STDOLD);

print " check .log file\n This should show in the terminal\n"; 

This works for me.. but in the end of the log file i have digit "1" printed i don't know why..I believe it is the timestamp being printed. I need to remove it.. do u know why is it happening?

Answer 1

It sounds like you want to redirect the output from the program to a file?

To do that from the command line, enter

perl myprogram.pl > myoutput.txt

---

If you want everything printed to STDOUT to go to a file then just open it as a file handle at the start of your program.

Like this

open STDOUT, '>', 'myoutput.txt' or die $!;

Answer 2

Any file handle you assign to the typeglob *::STDOUT will become STDOUT.

if ( my $fh = FileHandle->new( ">>$stdout_path" )) {
    *::STDOUT = $fh;
}

Although I normally usually only redirect STDERR to STDOUT or a file.

Answer 3

I would try the following (avoiding using double quotes plus using a "clear then append" approach:

:
:
my $output = "main fucntion to be called???\n"; 

open(OUTFILE, '> output1.txt') || die "could not clear down output file"; 
close OUTFILE;
open(OUTFILE, '>> output1.txt') || die "could not open append output file"; 

print OUTFILE "$output\n"; ## Notice, there is not a comma after the file handle and the string to be output 

close OUTFILE;
:
:

No need for braces in the close statement. The first open effectively emptys the file. The second is an open-extend (or append). I assume you will then use print OUTFILE ... throughout and move the second close Output; to the end of your script.

OR...

:
:
my $output = "main fucntion to be called???\n"; 

open(STDOUT, '> output1.txt') || die "could not clear down output file"; 
close STDOUT;
open(STDOUT, '>> output1.txt') || die "could not open append output file"; 

print "$output\n"; ## Notice, there is not a comma after the file handle and the string to be output 
:
:
close STDOUT;
:
:

Pretty sure this works - without need for STDOUT on every print command.

Answer 4

From what I understand, You are trying to send everything you "print" to a file. If that is what you want to do, it is fairly simple.

open (OUTPUT, '>output1.txt');
#whatever logic you want to do
print OUTPUT "whatever you want to print","temporary outputs";
#any other logic you have for computing the output
print OUTPUT "output1","output2";
#after completing all print statements, close the file handle
close(OUTPUT);

Basically, you need to give your File Handle (in my example OUTPUT) to "print" and then print like you would do normally. For example, if your original line is

print "not supported\n";

It will become

print OUTPUT "not supported\n";

Answer 5

You can use select to set the default filehandle for print:

open(my $OUTFILE, '>', 'output1.txt') || die "could not open output file: $!";
select $OUTFILE;
print $output;