Perl equivalent to unix script

[Mike]

Ok. . . Well, I'm sure here comes another dumb question. I'm fairly
handy with unix and unix scripting, however, I'm terrible at perl.

What I'm looking to do with a perl script is the equivalent of the
following unix (bash) script:

cat tempfile1 | sort > newfile2; rm tempfile1

I'm not completely comfortable with file handling in perl, and I think
it should be easy to do, but I've been unsuccessful in trying to do it.

I'm essentially trying to sort the lines in a file (alphabetically),
and then output them to another file.

Thanks

Mike

 

[Mike]

Ok. . . Well, I'm sure here comes another dumb question. I'm fairly
handy with unix and unix scripting, however, I'm terrible at perl.

What I'm looking to do with a perl script is the equivalent of the
following unix (bash) script:

cat tempfile1 | sort > newfile2; rm tempfile1

I'm not completely comfortable with file handling in perl, and I think
it should be easy to do, but I've been unsuccessful in trying to do it.

I'm essentially trying to sort the lines in a file (alphabetically),
and then output them to another file.

Thanks

Mike

I guess I should have said that I don't want to handle this with a
system call either, I'd prefer to figure out, and learn how to do it
with purely perl.

Thanks

Mike

 

[jl_post]

What I'm looking to do with a perl script is the equivalent of the
following unix (bash) script:

cat tempfile1 | sort > newfile2; rm tempfile1

Just use the command:

I'm fairly handy with unix and unix
scripting, however, I'm terrible at perl.

Ah... yeah... I was the same way a few years ago: I was (fairly)
good at Unix scripting, but didn't know any Perl. All that changed
when I read O'Reilly's "Learning Perl" book (by Randal L. Schwartz and
Tom Phoenix). The chapters are easy to understand and the exercises
are laid out very well. The book will teach you things all decent Perl
programmers should know, as well as things that will save you literally
hours of debugging time later on. (It will also explain '<>' (the
diamond operator) in sufficient detail so that you can use it to
program quickly and more efficiently.)

I hope this helps, Mike.

-- Jean-Luc

 

[J. Gleixner]

Post what you've tried.

I guess I should have said that I don't want to handle this with a
system call either, I'd prefer to figure out, and learn how to do it
with purely perl.

If you want to figure it out, give the documentation a try.

perldoc -f open
perldoc -f sort
perldoc -f unlink
perldoc opentut

Helpful Web sites:

http://perldoc.perl.org/
http://bookmarks.cpan.org/search.cgi?cat=Training/Tutorials

 

[Ben Morrow]

[newsgroups trimmed, f'ups set]

Ok. . . Well, I'm sure here comes another dumb question. I'm fairly
handy with unix and unix scripting, however, I'm terrible at perl.

What I'm looking to do with a perl script is the equivalent of the
following unix (bash) script:

cat tempfile1 | sort > newfile2; rm tempfile1

I'm not completely comfortable with file handling in perl, and I think
it should be easy to do, but I've been unsuccessful in trying to do it.

perldoc -f open
"I/O Operators" in perlop
perldoc -f sort
perldoc -f print
perldoc -f unlink

Make an attempt to solve the problem yourself. If you fail, post what
you have, and we will help you fix it.

Ben

 

[usenet]

cat tempfile1 | sort > newfile2;

That's rather convoluted even for UNIX scripting. Why not:

sort tempfile1 > newfile2;

You cannot do this as a pure-Perl approach (ie, no shell redirects,
etc) any more simply. You could do something like this:

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

open (my $in, '<', '/tmp/tempfile1') or die "oops - $!\n";
open (my $out, '>', '/tmp/newfile2') or die "oops - $!\n";

print $out sort(<$in>);

close $in;
close $out;

unlink $in;

__END__

 

[Tintin]

Ok. . . Well, I'm sure here comes another dumb question. I'm fairly
handy with unix and unix scripting, however, I'm terrible at perl.

What I'm looking to do with a perl script is the equivalent of the
following unix (bash) script:

cat tempfile1 | sort > newfile2; rm tempfile1

Handy at Unix, but still using UUOC?

 

[Mumia W. (reading news)]

It looks like a one-liner in Perl.

perldoc File::Slurp
perldoc -f sort

 

[Peter J. Holzer]

Now try sorting a 4 GB file with that... Something that GNU sort can
easily do...

Use the right tool for the job.

hp

 

[Dr.Ruud]

Dan Mercer schreef:

usenet:

Even that's too convoluted - why not just
sort -o file file

Because that is not equivalent. For example you can't tell from what is
presented whether tempfile1 is still needed for something else, after
the sort.

 

[Dr.Ruud]

Dan Mercer schreef:

Dr.Ruud:

The original pipeline was:

cat tempfile1 | sort > newfile2; rm tempfile1

Fine, but you replied on a message with a changed one.

If sort would somehow fail, I assume (some copy of) "file" will remain
available, after a "sort -o file file".

 

[Peter J. Holzer]

If sort would somehow fail, I assume (some copy of) "file" will remain
available, after a "sort -o file file".

Depends on the implementation. With GNU sort this is not guaranteed.
After file has been completely read and (partially) sorted, it is opened
for writing. If GNU sort fails after that you are left with only a
partial copy. If you have enough space it is safer to invoke

sort file > file.$$ && mv file.$$ file

hp