added skeleton for all currently available languages

sheets/_perl/1line

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+#
+# FILE SPACING 
+# ------------
+
+# Double space a file
+perl -pe '$\="\n"'
+perl -pe 'BEGIN { $\="\n" }'
+perl -pe '$_ .= "\n"'
+perl -pe 's/$/\n/'
+perl -nE 'say'
+
+# Double space a file, except the blank lines
+perl -pe '$_ .= "\n" unless /^$/'
+perl -pe '$_ .= "\n" if /\S/'
+
+# Triple space a file
+perl -pe '$\="\n\n"'
+perl -pe '$_.="\n\n"'
+
+# N-space a file
+perl -pe '$_.="\n"x7'
+
+# Add a blank line before every line
+perl -pe 's//\n/'
+
+# Remove all blank lines
+perl -ne 'print unless /^$/'
+perl -lne 'print if length'
+perl -ne 'print if /\S/'
+
+# Remove all consecutive blank lines, leaving just one
+perl -00 -pe ''
+perl -00pe0
+
+# Compress/expand all blank lines into N consecutive ones
+perl -00 -pe '$_.="\n"x4'
+
+# Fold a file so that every set of 10 lines becomes one tab-separated line
+perl -lpe '$\ = $. % 10 ? "\t" : "\n"'
+
+#
+# LINE NUMBERING
+# --------------
+
+# Number all lines in a file
+perl -pe '$_ = "$. $_"'
+
+# Number only non-empty lines in a file
+perl -pe '$_ = ++$a." $_" if /./'
+
+# Number and print only non-empty lines in a file (drop empty lines)
+perl -ne 'print ++$a." $_" if /./'
+
+# Number all lines but print line numbers only non-empty lines
+perl -pe '$_ = "$. $_" if /./'
+
+# Number only lines that match a pattern, print others unmodified
+perl -pe '$_ = ++$a." $_" if /regex/'
+
+# Number and print only lines that match a pattern
+perl -ne 'print ++$a." $_" if /regex/'
+
+# Number all lines, but print line numbers only for lines that match a pattern
+perl -pe '$_ = "$. $_" if /regex/'
+
+# Number all lines in a file using a custom format (emulate cat -n)
+perl -ne 'printf "%-5d %s", $., $_'
+
+# Print the total number of lines in a file (emulate wc -l)
+perl -lne 'END { print $. }'
+perl -le 'print $n=()=<>'
+perl -le 'print scalar(()=<>)'
+perl -le 'print scalar(@foo=<>)'
+perl -ne '}{print $.'
+perl -nE '}{say $.'
+
+# Print the number of non-empty lines in a file
+perl -le 'print scalar(grep{/./}<>)'
+perl -le 'print ~~grep{/./}<>'
+perl -le 'print~~grep/./,<>'
+perl -E 'say~~grep/./,<>'
+
+# Print the number of empty lines in a file
+perl -lne '$a++ if /^$/; END {print $a+0}'
+perl -le 'print scalar(grep{/^$/}<>)'
+perl -le 'print ~~grep{/^$/}<>'
+perl -E 'say~~grep{/^$/}<>'
+
+# Print the number of lines in a file that match a pattern (emulate grep -c)
+perl -lne '$a++ if /regex/; END {print $a+0}'
+perl -nE '$a++ if /regex/; END {say $a+0}'
+
+#
+# CALCULATIONS
+# ------------
+
+# Check if a number is a prime
+perl -lne '(1x$_) !~ /^1?$|^(11+?)\1+$/ && print "$_ is prime"'
+
+# Print the sum of all the fields on a line
+perl -MList::Util=sum -alne 'print sum @F'
+
+# Print the sum of all the fields on all lines
+perl -MList::Util=sum -alne 'push @S,@F; END { print sum @S }'
+perl -MList::Util=sum -alne '$s += sum @F; END { print $s }'
+
+# Shuffle all fields on a line
+perl -MList::Util=shuffle -alne 'print "@{[shuffle @F]}"'
+perl -MList::Util=shuffle -alne 'print join " ", shuffle @F'
+
+# Find the minimum element on a line
+perl -MList::Util=min -alne 'print min @F'
+
+# Find the minimum element over all the lines
+perl -MList::Util=min -alne '@M = (@M, @F); END { print min @M }'
+perl -MList::Util=min -alne '$min = min @F; $rmin = $min unless defined $rmin && $min > $rmin; END { print $rmin }'
+
+# Find the maximum element on a line
+perl -MList::Util=max -alne 'print max @F'
+
+# Find the maximum element over all the lines
+perl -MList::Util=max -alne '@M = (@M, @F); END { print max @M }'
+
+# Replace each field with its absolute value
+perl -alne 'print "@{[map { abs } @F]}"'
+
+# Find the total number of fields (words) on each line
+perl -alne 'print scalar @F'
+
+# Print the total number of fields (words) on each line followed by the line
+perl -alne 'print scalar @F, " $_"'
+
+# Find the total number of fields (words) on all lines
+perl -alne '$t += @F; END { print $t}'
+
+# Print the total number of fields that match a pattern
+perl -alne 'map { /regex/ && $t++ } @F; END { print $t }'
+perl -alne '$t += /regex/ for @F; END { print $t }'
+perl -alne '$t += grep /regex/, @F; END { print $t }'
+
+# Print the total number of lines that match a pattern
+perl -lne '/regex/ && $t++; END { print $t }'
+
+# Print the number PI to n decimal places
+perl -Mbignum=bpi -le 'print bpi(n)'
+
+# Print the number PI to 39 decimal places
+perl -Mbignum=PI -le 'print PI'
+
+# Print the number E to n decimal places
+perl -Mbignum=bexp -le 'print bexp(1,n+1)'
+
+# Print the number E to 39 decimal places
+perl -Mbignum=e -le 'print e'
+
+# Print UNIX time (seconds since Jan 1, 1970, 00:00:00 UTC)
+perl -le 'print time'
+
+# Print GMT (Greenwich Mean Time) and local computer time
+perl -le 'print scalar gmtime'
+perl -le 'print scalar localtime'
+
+# Print local computer time in H:M:S format
+perl -le 'print join ":", (localtime)[2,1,0]'
+
+# Print yesterday's date
+perl -MPOSIX -le '@now = localtime; $now[3] -= 1; print scalar localtime mktime @now'
+
+# Print date 14 months, 9 days and 7 seconds ago
+perl -MPOSIX -le '@now = localtime; $now[0] -= 7; $now[4] -= 14; $now[7] -= 9; print scalar localtime mktime @now'
+
+# Prepend timestamps to stdout (GMT, localtime)
+tail -f logfile | perl -ne 'print scalar gmtime," ",$_'
+tail -f logfile | perl -ne 'print scalar localtime," ",$_'
+
+# Calculate factorial of 5
+perl -MMath::BigInt -le 'print Math::BigInt->new(5)->bfac()'
+perl -le '$f = 1; $f *= $_ for 1..5; print $f'
+
+# Calculate greatest common divisor (GCM)
+perl -MMath::BigInt=bgcd -le 'print bgcd(@list_of_numbers)'
+
+# Calculate GCM of numbers 20 and 35 using Euclid's algorithm
+perl -le '$n = 20; $m = 35; ($m,$n) = ($n,$m%$n) while $n; print $m'
+
+# Calculate least common multiple (LCM) of numbers 35, 20 and 8
+perl -MMath::BigInt=blcm -le 'print blcm(35,20,8)'
+
+# Calculate LCM of 20 and 35 using Euclid's formula: n*m/gcd(n,m)
+perl -le '$a = $n = 20; $b = $m = 35; ($m,$n) = ($n,$m%$n) while $n; print $a*$b/$m'
+
+# Generate 10 random numbers between 5 and 15 (excluding 15)
+perl -le '$n=10; $min=5; $max=15; $, = " "; print map { int(rand($max-$min))+$min } 1..$n'
+
+# Find and print all permutations of a list
+perl -MAlgorithm::Permute -le '$l = [1,2,3,4,5]; $p = Algorithm::Permute->new($l); print @r while @r = $p->next'
+
+# Generate the power set
+perl -MList::PowerSet=powerset -le '@l = (1,2,3,4,5); for (@{powerset(@l)}) { print "@$_" }'
+
+# Convert an IP address to unsigned integer
+perl -le '$i=3; $u += ($_<<8*$i--) for "127.0.0.1" =~ /(\d+)/g; print $u'
+perl -le '$ip="127.0.0.1"; $ip =~ s/(\d+)\.?/sprintf("%02x", $1)/ge; print hex($ip)'
+perl -le 'print unpack("N", 127.0.0.1)'
+perl -MSocket -le 'print unpack("N", inet_aton("127.0.0.1"))'
+
+# Convert an unsigned integer to an IP address
+perl -MSocket -le 'print inet_ntoa(pack("N", 2130706433))'
+perl -le '$ip = 2130706433; print join ".", map { (($ip>>8*($_))&0xFF) } reverse 0..3'
+perl -le '$ip = 2130706433; $, = "."; print map { (($ip>>8*($_))&0xFF) } reverse 0..3'
+
+# 
+# STRING CREATION AND ARRAY CREATION
+# ----------------------------------
+
+# Generate and print the alphabet
+perl -le 'print a..z'
+perl -le 'print ("a".."z")'
+perl -le '$, = ","; print ("a".."z")'
+perl -le 'print join ",", ("a".."z")'
+
+# Generate and print all the strings from "a" to "zz"
+perl -le 'print ("a".."zz")'
+perl -le 'print "aa".."zz"'
+
+# Create a hex lookup table
+@hex = (0..9, "a".."f")
+
+# Convert a decimal number to hex using @hex lookup table
+perl -le '$num = 255; @hex = (0..9, "a".."f"); while ($num) { $s = $hex[($num%16)&15].$s; $num = int $num/16 } print $s'
+perl -le '$hex = sprintf("%x", 255); print $hex'
+perl -le '$num = "ff"; print hex $num'
+
+# Generate a random 8 character password
+perl -le 'print map { ("a".."z")[rand 26] } 1..8'
+perl -le 'print map { ("a".."z", 0..9)[rand 36] } 1..8'
+
+# Create a string of specific length
+perl -le 'print "a"x50'
+
+# Create a repeated list of elements
+perl -le '@list = (1,2)x20; print "@list"'
+
+# Create an array from a string
+@months = split ' ', "Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec"
+@months = qw/Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec/
+
+# Create a string from an array
+@stuff = ("hello", 0..9, "world"); $string = join '-', @stuff
+
+# Find the numeric values for characters in the string
+perl -le 'print join ", ", map { ord } split //, "hello world"'
+
+# Convert a list of numeric ASCII values into a string
+perl -le '@ascii = (99, 111, 100, 105, 110, 103); print pack("C*", @ascii)'
+perl -le '@ascii = (99, 111, 100, 105, 110, 103); print map { chr } @ascii'
+
+# Generate an array with odd numbers from 1 to 100
+perl -le '@odd = grep {$_ % 2 == 1} 1..100; print "@odd"'
+perl -le '@odd = grep { $_ & 1 } 1..100; print "@odd"'
+
+# Generate an array with even numbers from 1 to 100
+perl -le '@even = grep {$_ % 2 == 0} 1..100; print "@even"'
+
+# Find the length of the string
+perl -le 'print length "one-liners are great"'
+
+# Find the number of elements in an array
+perl -le '@array = ("a".."z"); print scalar @array'
+perl -le '@array = ("a".."z"); print $#array + 1'
+
+# 
+# TEXT CONVERSION AND SUBSTITUTION
+# --------------------------------
+
+# ROT13 a string
+'y/A-Za-z/N-ZA-Mn-za-m/'
+
+# ROT 13 a file
+perl -lpe 'y/A-Za-z/N-ZA-Mn-za-m/' file
+
+# Base64 encode a string
+perl -MMIME::Base64 -e 'print encode_base64("string")'
+perl -MMIME::Base64 -0777 -ne 'print encode_base64($_)' file
+
+# Base64 decode a string
+perl -MMIME::Base64 -le 'print decode_base64("base64string")'
+perl -MMIME::Base64 -ne 'print decode_base64($_)' file
+
+# URL-escape a string
+perl -MURI::Escape -le 'print uri_escape($string)'
+
+# URL-unescape a string
+perl -MURI::Escape -le 'print uri_unescape($string)'
+
+# HTML-encode a string
+perl -MHTML::Entities -le 'print encode_entities($string)'
+
+# HTML-decode a string
+perl -MHTML::Entities -le 'print decode_entities($string)'
+
+# Convert all text to uppercase
+perl -nle 'print uc'
+perl -ple '$_=uc'
+perl -nle 'print "\U$_"'
+
+# Convert all text to lowercase
+perl -nle 'print lc'
+perl -ple '$_=lc'
+perl -nle 'print "\L$_"'
+
+# Uppercase only the first word of each line
+perl -nle 'print ucfirst lc'
+perl -nle 'print "\u\L$_"'
+
+# Invert the letter case
+perl -ple 'y/A-Za-z/a-zA-Z/'
+
+# Camel case each line
+perl -ple 's/(\w+)/\u$1/g'
+perl -ple 's/(?<![\'])(\w+)/\u\1/g'
+
+# Strip leading whitespace (spaces, tabs) from the beginning of each line
+perl -ple 's/^[ \t]+//'
+perl -ple 's/^\s+//'
+
+# Strip trailing whitespace (space, tabs) from the end of each line
+perl -ple 's/[ \t]+$//'
+
+# Strip whitespace from the beginning and end of each line
+perl -ple 's/^[ \t]+|[ \t]+$//g'
+
+# Convert UNIX newlines to DOS/Windows newlines
+perl -pe 's|\n|\r\n|'
+
+# Convert DOS/Windows newlines to UNIX newlines
+perl -pe 's|\r\n|\n|'
+
+# Convert UNIX newlines to Mac newlines
+perl -pe 's|\n|\r|'
+
+# Substitute (find and replace) "foo" with "bar" on each line
+perl -pe 's/foo/bar/'
+
+# Substitute (find and replace) all "foo"s with "bar" on each line
+perl -pe 's/foo/bar/g'
+
+# Substitute (find and replace) "foo" with "bar" on lines that match "baz"
+perl -pe '/baz/ && s/foo/bar/'
+
+# Binary patch a file (find and replace a given array of bytes as hex numbers)
+perl -pi -e 's/\x89\xD8\x48\x8B/\x90\x90\x48\x8B/g' file
+
+
+#
+# SELECTIVE PRINTING AND DELETING OF CERTAIN LINES
+# ------------------------------------------------
+
+# Print the first line of a file (emulate head -1)
+perl -ne 'print; exit'
+
+# Print the first 10 lines of a file (emulate head -10)
+perl -ne 'print if $. <= 10'
+perl -ne '$. <= 10 && print'
+perl -ne 'print if 1..10'
+
+# Print the last line of a file (emulate tail -1)
+perl -ne '$last = $_; END { print $last }'
+perl -ne 'print if eof'
+
+# Print the last 10 lines of a file (emulate tail -10)
+perl -ne 'push @a, $_; @a = @a[@a-10..$#a]; END { print @a }'
+
+# Print only lines that match a regular expression
+perl -ne '/regex/ && print'
+
+# Print only lines that do not match a regular expression
+perl -ne '!/regex/ && print'
+
+# Print the line before a line that matches a regular expression
+perl -ne '/regex/ && $last && print $last; $last = $_'
+
+# Print the line after a line that matches a regular expression
+perl -ne 'if ($p) { print; $p = 0 } $p++ if /regex/'
+
+# Print lines that match regex AAA and regex BBB in any order
+perl -ne '/AAA/ && /BBB/ && print'
+
+# Print lines that don't match match regexes AAA and BBB
+perl -ne '!/AAA/ && !/BBB/ && print'
+
+# Print lines that match regex AAA followed by regex BBB followed by CCC
+perl -ne '/AAA.*BBB.*CCC/ && print'
+
+# Print lines that are 80 chars or longer
+perl -ne 'print if length >= 80'
+
+# Print lines that are less than 80 chars in length
+perl -ne 'print if length < 80'
+
+# Print only line 13
+perl -ne '$. == 13 && print && exit'
+
+# Print all lines except line 27
+perl -ne '$. != 27 && print'
+perl -ne 'print if $. != 27'
+
+# Print only lines 13, 19 and 67
+perl -ne 'print if $. == 13 || $. == 19 || $. == 67'
+perl -ne 'print if int($.) ~~ (13, 19, 67)' 
+
+# Print all lines between two regexes (including lines that match regex)
+perl -ne 'print if /regex1/../regex2/'
+
+# Print all lines from line 17 to line 30
+perl -ne 'print if $. >= 17 && $. <= 30'
+perl -ne 'print if int($.) ~~ (17..30)'
+perl -ne 'print if grep { $_ == $. } 17..30'
+
+# Print the longest line
+perl -ne '$l = $_ if length($_) > length($l); END { print $l }'
+
+# Print the shortest line
+perl -ne '$s = $_ if $. == 1; $s = $_ if length($_) < length($s); END { print $s }'
+
+# Print all lines that contain a number
+perl -ne 'print if /\d/'
+
+# Find all lines that contain only a number
+perl -ne 'print if /^\d+$/'
+
+# Print all lines that contain only characters
+perl -ne 'print if /^[[:alpha:]]+$/'
+
+# Print every second line
+perl -ne 'print if $. % 2'
+
+# Print every second line, starting the second line
+perl -ne 'print if $. % 2 == 0'
+
+# Print all lines that repeat
+perl -ne 'print if ++$a{$_} == 2'
+
+# Print all unique lines
+perl -ne 'print unless $a{$_}++'
+
+# Print the first field (word) of every line (emulate cut -f 1 -d ' ')
+perl -alne 'print $F[0]'
+
+# 
+# HANDY REGULAR EXPRESSIONS
+# -------------------------
+
+# Match something that looks like an IP address
+/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/
+/^(\d{1,3}\.){3}\d{1,3}$/
+
+# Test if a number is in range 0-255
+/^([0-9]|[0-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])$/
+
+# Match an IP address
+my $ip_part = qr|([0-9]|[0-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])|;
+if ($ip =~ /^($ip_part\.){3}$ip_part$/) {
+ say "valid ip";
+}
+
+# Check if the string looks like an email address
+/\S+@\S+\.\S+/
+
+# Check if the string is a decimal number
+/^\d+$/
+/^[+-]?\d+$/
+/^[+-]?\d+\.?\d*$/
+
+# Check if the string is a hexadecimal number
+/^0x[0-9a-f]+$/i
+
+# Check if the string is an octal number
+/^0[0-7]+$/
+
+# Check if the string is binary
+/^[01]+$/
+
+# Check if a word appears twice in the string
+/(word).*\1/
+
+# Increase all numbers by one in the string
+$str =~ s/(\d+)/$1+1/ge
+
+# Extract HTTP User-Agent string from the HTTP headers
+/^User-Agent: (.+)$/
+
+# Match printable ASCII characters
+/[ -~]/
+
+# Match unprintable ASCII characters
+/[^ -~]/
+
+# Match text between two HTML tags
+m|<strong>([^<]*)</strong>|
+m|<strong>(.*?)</strong>|
+
+# Replace all <b> tags with <strong>
+$html =~ s|<(/)?b>|<$1strong>|g
+
+# Extract all matches from a regular expression
+my @matches = $text =~ /regex/g;
+
+#
+# PERL TRICKS
+# -----------
+
+# Print the version of a Perl module
+perl -MModule -le 'print $Module::VERSION'
+perl -MLWP::UserAgent -le 'print $LWP::UserAgent::VERSION'
+
+
+# PERL ONE-LINERS EXPLAINED E-BOOK
+# --------------------------------
+# http://www.catonmat.net/blog/perl-book/