perl notes
local perl setup
install perlbrew
\curl -L http://install.perlbrew.pl | bash
install local perl and cpanm
After restarting your shell or sourcing the files installed by perlbrew you can build a new perl version that can be installed locally. Afterward, you can install cpanm to install perl packages using the local perl you just built.
PERL_VERSION="perl-5.35.10"
perlbrew install ${PERL_VERSION}
perlbrew switch ${PERL_VERSION}
perlbrew install-cpanm
find files with perl
Try the handy find2perl utility that comes with perl and uses the File::Find
package. It writes a little script for you that you can adapt. See the
perldoc site for further details.
An example from the documentation
find2perl / -name .nfs\* -mtime +7 \
-exec rm -f {} \; -o -fstype nfs -prune
``
Gives you a `wanted` subroutine like so:
```perl
sub wanted {
/^\.nfs.*\z/s &&
(($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_)) &&
int(-M _) > 7 &&
unlink($_)
||
($nlink || (($dev, $ino, $mode, $nlink, $uid, $gid) = lstat($_))) &&
$dev < 0 &&
($File::Find::prune = 1);
}
Here’s a modification that gives you files ending in txt modified between 50 and 20 days ago.
sub wanted {
my ($dev,$ino,$mode,$nlink,$uid,$gid);
/\.txt\z/s &&
(($dev,$ino,$mode,$nlink,$uid,$gid) = lstat($_)) &&
(int(-M _) < 50) && (int(-M _) > 20)
&& print("$name\n");
}
find perl module location
Basically, @INC gives you the locations of modules; %INC is a hash with the
keys as modules and values as locations of the module.
perl -MXSLoader -lE 'map { print join(" ", $_, "=>", $INC{$_}); } keys %INC'
You can also achieve the same effect of figuring out where the module is located
using perldoc.
perldoc -lm XSLoader
perl DBD::mysql
By default DBD::mysql does not compile in ssl. The simplest way to have it
compile with ssl is to set the environmental variable, export DBD_MYSQL_SSL=1.
If you install it with cpanm, for instance, it will install correctly if you
set the environmental variable.
There are other environmental variables, too, that can be set, mostly to assist
with testing. See perldoc DBD::mysql.
perl text manipulation
command line
split lines automatically on white-space
Splitting text on the command line with -a creates @F automatically, which
has all of the processed text. It must be used with either the -n or -p
options, which both place a loop around your script. The difference being that
-p executes your commands and prints the value of $_ afterward.
perl -nalE '{ print $F[3]; }' some_file
specify how to split each line with -F
Specifying -F implicitly sets -a and -n. To split using the semicolon try:
perl -F';' -lE '{ print $F[2]; }' some_file
read csv
use Text::CSV_XS;
use Text::Iconv;
my $csv_reader = Text::CSV_XS->new({auto_diag => 1, binary => 1});
write csv
use Text::CSV_XS;
my $csv_writer = Text::CSV_XS->new({
binary => 1, auto_diag => 1, always_quote => 1, eol => "\n"
});
read xls
use Spreadsheet::ParseExcel;
my $parser = Spreadsheet::ParseExcel->new();
my $workbook = $parser->parse($file);
read xlsx
Note, that you do not necessarily need to use the converter.
use Spreadsheet::XLSX;
use Text::Iconv;
my $converter = Text::Iconv->new("utf-8", "windows-1251");
my $in_excel = Spreadsheet::XLSX->new($file, $converter);
write xlsx
use Excel::Writer::XLSX;
my $workbook = Excel::Writer::XLSX->new("$out_ext.xlsx");
$workbook->set_properties(
title => "data created by $prog_name on $now_time",
author => 'TS Wingo',
comments => 'created with perl and Excel::Writer::XLSX'
);
perl serializing data
JSON - for machines
use JSON
my $json = new JSON;
print $json->pretty(1)->encode(\%data);
YAML - for humans
use YAML qw(Dump Bless);
print Dump(\%data);
perl dates/times
read dates and make a DateTime object
use DateTime;
use DateTime::Format::Strptime;
# some common ones I've (unfortuneately) encountered
# YYYY-MM-DD
my $strp_dt_iso = DateTime::Format::Strptime->new(
pattern => '%F', on_error => 'croak'
);
# MM/DD/YYYY HH:MM:SS AM/PM (12h time)
my $strp_dt_us_12h = DateTime::Format::Strptime->new(
pattern => '%m/%d/%Y %I:%M:%S %p', on_error => 'croak'
);
# MM/DD/YYYY
my $strp_dt_us = DateTime::Format::Strptime->new(
pattern => '%m/%d/%Y', on_error => 'croak'
);
# DD-Mos-YY (month = 3 letter abbreviation)
my $strp_dt_crazy = DateTime::Format::Strptime->new(
pattern => '%d-%B-%y', on_error => 'croak'
);
# parse
$dt = $strp_dt_us->parse_datetime($this_data{date});
## get current time?
use Time::localtime;
# time
my $now_time = ctime();
# date
my $now_timestamp = sprintf("%d-%d-%d", eval(localtime->year() + 1900),
eval(localtime->mon() + 1), localtime->mday());
## file modified time
use Time::localtime;
use File::stat;
$date_string = ctime(stat($file)->mtime);
perl HERE documents
Here’s an overview how to use them.
non-interpreted
my $cmd = <<'EOF';
#!/bin/sh
touch file.tmp
EOF
print $cmd;
interpreted
my $cmd = <<"EOF";
#!/bin/sh
touch $this_file
EOF
print $cmd;
white space
If you have indented things and you want the here document to be alignged just tell perl to get rid of the leading whitespace like so.
(my $cmd = <<"EOF") =~ s/\A\s+//gm;
...
EOF
perl’s q{} or qq{} commands
Another option is just to use qq or q (depending on whether you want to interpolate things).
(my $cmd = qq{
#!/bin/sh
touch $this_file
}) =~ s/\A\s+//mg;
perl error handling
Lots of people like Try::Tiny, which is fine. I have used the following approach.
Basically, you just put the thing that might fail in an eval block, as per usual, and inspect the return value (without necessarily depend on $@ to have the right error since it can be clobbered sometimes).
eval {
# do something that fails
1 / 0;
# return true to indicate success
1;
}
or do {
# say something about it and have a default statement
my $error = $@ || 'unknown failure';
# notice you'll need the semi-colon unless you're at the end of a block
};
See this stackoverflow and perltv.org for more details.
perl cheat sheet
Originally found here.
CONTEXTS SIGILS ARRAYS HASHES
void $scalar whole: @array %hash
scalar @array slice: @array[0, 2] @hash{'a', 'b'}
list %hash element: $array[0] $hash{'a'}
&sub
*glob SCALAR VALUES
number, string, reference, glob, undef
REFERENCES
\ references $$foo[1] aka $foo->[1]
$@%&* dereference $$foo{bar} aka $foo->{bar}
[] anon. arrayref ${$$foo[1]}[2] aka $foo->[1]->[2]
{} anon. hashref ${$$foo[1]}[2] aka $foo->[1][2]
\() list of refs
NUMBERS vs STRINGS LINKS
OPERATOR PRECEDENCE = = perl.plover.com
-> + . search.cpan.org
++ -- == != eq ne cpan.org
** < > <= >= lt gt le ge pm.org
! ~ \ u+ u- <=> cmp tpj.com
=~ !~ perldoc.com
* / % x SYNTAX
+ - . for (LIST) { }, for (a;b;c) { }
<< >> while ( ) { }, until ( ) { }
named uops if ( ) { } elsif ( ) { } else { }
< > <= >= lt gt le ge unless ( ) { } elsif ( ) { } else { }
== != <=> eq ne cmp for equals foreach (ALWAYS)
&
| ^ REGEX METACHARS REGEX MODIFIERS
&& ^ string begin /i case insens.
|| $ str. end (before \n) /m line based ^$
.. ... + one or more /s . includes \n
?: * zero or more /x ign. wh.space
= += -= *= etc. ? zero or one /g global
, => {3,7} repeat in range
list ops () capture REGEX CHARCLASSES
not (?:) no capture . == [^\n]
and [] character class \s == [\x20\f\t\r\n]
or xor | alternation \w == [A-Za-z0-9_]
\b word boundary \d == [0-9]
\z string end \S, \W and \D negate
DO
use strict; DON'T LINKS
use warnings; "$foo" perl.com
my $var; $$variable_name perlmonks.org
open() or die $!; `$userinput` use.perl.org
use Modules; /$userinput/ perl.apache.org
parrotcode.org
FUNCTION RETURN LISTS
stat localtime caller SPECIAL VARIABLES
0 dev 0 second 0 package $_ default variable
1 ino 1 minute 1 filename $0 program name
2 mode 2 hour 2 line $/ input separator
3 nlink 3 day 3 subroutine $\ output separator
4 uid 4 month-1 4 hasargs $| autoflush
5 gid 5 year-1900 5 wantarray $! sys/libcall error
6 rdev 6 weekday 6 evaltext $@ eval error
7 size 7 yearday 7 is_require $$ process ID
8 atime 8 is_dst 8 hints $. line number
9 mtime 9 bitmask @ARGV command line args
10 ctime just use @INC include paths
11 blksz POSIX:: 3..9 only @_ subroutine args
12 blcks strftime! with EXPR %ENV environment