Zaahir Moolla
commit
442ea5c5b4
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{
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"id": "perl_cheat_sheet",
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"name": "Perl",
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"description": "Essential Perl basic syntax, methods, functions, variables, references and data structure ",
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"metadata": {
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"sourceName": "Cheatography",
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"sourceUrl": "http://www.cheatography.com/mishin/cheat-sheets/perl-reference-card/"
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},
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"aliases": [
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"perl"
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],
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"template_type": "code",
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"section_order": ["Input/Output", "Scalars and Strings", "Arrays and Lists", "Hashes", "Basic Syntax", "References and Data Structures", "System Interaction"],
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"sections": {
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"Input/Output": [{
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"val": "Open file for input",
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"key": "open(INFILE,\"in.txt\") or die;"
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}, {
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"val": "Open file with encoding",
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"key": "open(INFILE,\"<:utf8\",\"file\");"
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}, {
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"val": "Open anonymous temp file",
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"key": "open(TMP,\"+>\", undef);"
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}, {
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"val": "Open output file",
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"key": "open(OUT,\">out.txt\") or die;"
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}, {
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"val": "Open file for append",
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"key": "open(LOG,\">>my.log\") or die;"
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}, {
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"val": "Get next line",
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"key": "$line = <INFILE>;"
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}, {
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"val": "Slurp infile",
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"key": "@lines = <INFILE>;"
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}, {
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"val": "Print to STDERR",
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"key": "print STDERR \"Warning 1.\\n\";"
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}, {
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"val": "Close filehandle",
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"key": "close INFILE;"
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}],
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"Scalars and Strings": [{
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"val": "Discard trailing \\n",
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"key": "chomp($str);"
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}, {
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"val": "$v becomes trailing char",
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"key": "$v = chop($str);"
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}, {
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"val": "String comparison",
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"key": "eq, ne, lt, gt, le, ge, cmp"
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}, {
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"val": "Find index of $x in $str,",
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"key": "$v = index($str, $x);"
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}, {
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"val": "Starting from left or right",
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"key": "$v = rindex($str, $x);"
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}, {
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"val": "Extract substring",
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"key": "$v = substr($str, $strt, $len);"
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}, {
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"val": "Count the digits in $sky",
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"key": "$cnt = $sky =~ tr\/0-9\/\/;"
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}, {
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"val": "Change non-alphas to space",
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"key": "$str =~ tr\/a-zA-Z\/\/cs;"
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}, {
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"val": "Format string",
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"key": "$v = sprintf(“%10s %08d”,$s,$n);"
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}],
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"Arrays and Lists": [{
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"val": "Array initialization",
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"key": "@a = (1..5);"
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}, {
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"val": "Number of elements in @a",
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"key": "$i = @a;"
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}, {
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"val": "Swap $a and $b",
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"key": "($a, $b) = ($b, $a);"
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}, {
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"val": "Access to index 1",
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"key": "$x = $a\\[1\\];"
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}, {
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"val": "Last index in @a",
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"key": "$i = $#a;"
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}, {
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"val": "Appends $s to @a",
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"key": "push(@a, $s);"
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}, {
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"val": "Removes last element",
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"key": "$a = pop(@a);"
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}, {
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"val": "Remove last char (per el.)",
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"key": "chop(@a);"
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}, {
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"val": "Removes first element",
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"key": "$a = shift(@a);"
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}, {
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"val": "Reverse @a",
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"key": "reverse(@a);"
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}, {
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"val": "Sort numerically",
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"key": "@a = sort\\{$ela <=> $elb\\}(@a);"
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}, {
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"val": "Split string into @a",
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"key": "@a = split(\/-\/,$s);"
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}],
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"Hashes": [{
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"val": "Hash initialization",
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"key": "%h=(k1 => “val1”,k2 => 3);"
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}, {
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"val": "Recall value",
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"key": "$val = $map\\{k1\\};"
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}, {
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"val": "Array of keys and values",
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"key": "@a = %h;"
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}, {
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"val": "Create hash from array",
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"key": "%h = @a;"
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}, {
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"val": "Iterate over list of keys",
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"key": "foreach $k (keys(%h))\\{..\\}"
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}, {
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"val": "Iterate over list of values",
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"key": "foreach $v (vals(%h))\\{..\\}"
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}, {
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"val": "Iterate over key-value-pairs",
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"key": "while (($k,$v)=each %h)\\{..\\}"
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}, {
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"val": "Delete key",
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"key": "delete $h\\{k1\\};"
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}],
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"Basic Syntax": [{
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"val": "Read command line params",
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"key": "($a, $b) = shift(@ARGV);"
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}, {
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"val": "Define subroutine",
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"key": "sub p\\{my $var = shift; ...\\}"
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}, {
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"val": "Execute subroutine",
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"key": "p(“bla”);"
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}, {
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"val": "Conditional",
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"key": "if(expr)\\{\\} elsif \\{\\} else \\{\\}"
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}, {
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"val": "Negative conditional",
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"key": "unless (expr)\\{\\}"
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}, {
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"val": "While-loop",
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"key": "while (expr)\\{\\}"
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}, {
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"val": "Until-loop",
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"key": "until (expr)\\{\\}"
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}, {
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"val": "Postcheck until-loop",
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"key": "do \\{\\} until (expr)"
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}, {
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"val": "For-loop",
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"key": "for($i=1; $i<=10; $i++)\\{\\}"
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}, {
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"val": "Foreach-loop",
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"key": "foreach $i (@list)\\{\\}"
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}, {
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"val": "End loop, skip to next, jump to top",
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"key": "last, next, redo"
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}],
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"References and Data Structures": [{
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"val": "Reference to array",
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"key": "$aref = \\@a;"
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}, {
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"val": "Anonymous array",
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"key": "$aref = \\[1,\"foo\",undef,13\\];"
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}, {
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"val": "Access element of array",
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"key": "[$el = $aref->\\[0\\];] / [$el = @\\{$aref\\}\\[0\\];]"
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}, {
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"val": "Copy array",
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"key": "$aref2 = \\[@\\{$aref1\\}\\];"
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}, {
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"val": "Reference to hash",
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"key": "$href = \\%h;"
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}, {
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"val": "Anonymous hash",
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"key": "$href =\\{APR => 4,AUG => 8\\};"
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}, {
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"val": "Access element of hash",
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"key": "[$el = $href->\\{APR\\};] / [$el = %\\{$href\\}\\{APR\\};]"
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}, {
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"val": "Copy hash",
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"key": "$href2 = \\{%\\{$href1\\}\\};"
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}, {
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"val": "Checks if $r points to hash",
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"key": "if (ref($r) eq \"HASH\") \\{\\}"
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}, {
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"val": "2-dim array",
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"key": "@a = (\\[1, 2\\],\\[3, 4\\]);"
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}, {
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"val": "Access 2-dim array",
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"key": "$i = $a\\[0\\]\\[1\\];"
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}],
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"System Interaction": [{
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"val": "System call",
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"key": "system(“cat $f|sort -u>$f.s”);"
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}, {
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"val": "Catch output",
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"key": "@a = readpipe(“lsmod”);"
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}, {
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"val": "Catch output",
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"key": "$today = “Today: “.date;"
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}, {
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"val": "Change root",
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"key": "chroot(“\/home\/user\/”);"
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}, {
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"val": "Operate on all c-files",
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"key": "while (<*.c>) \\{\\}'"
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}, {
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"val": "Delete file",
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"key": "unlink(“\/tmp\/file”);"
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}, {
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"val": "File test",
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"key": "if (-f “file.txt”)\\{...\\}"
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}]
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}
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}
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