What are the commonly used perl functions
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Common perl functions:
Chop and chomp:
My $line = "hello\ n"
Chomp $line; # deletes the "\ n" at the end of $line ($/ specified)
Chop $line; # removes the last character of $line
Split and join: # cutting function, glue function
$str = "A:B:C"
My @ arr = split/:/,$str; # @ arr = qw (A B C)
$str= join (",", @ arr); # $str= "AMagi BMagee C"
Scalar returns the number of array elements
My @ arr = (1, 2, 3, 4)
Print scalar (@ arr); # shows 4
My $num = @ arr; print $num; # shows 4
$num = $# arr; prnt $num; # display 3
Length returns scalar length
My $len = length ("ATCGAA")
Print $len; # shows 6
String interception function: substr (scalar, starting point, length)
My $seq = "ATGTAA"
My $code = substr ($seq,0,3)
Print $code; # shows ATG
Substr ($seq,0,3) = "TTG"
Print $seq; # shows TTGTAA
Scalar or array reverse order: reverse function
My @ arr = (1, 2, 3, 4)
My @ rev = reverse @ arr; # @ rev = (4, 3, 2, 1)
My $str = "ATCG"
My $rev = reverse $str; # $rev = "GCTA"
Shift, pop, unshift, push functions
My @ arr = (1, 2, 3, 4)
Take the first element of the array:
My $first = shift @ arr; # @ arr:
Take the last element of the array:
My $last = pop @ arr; # @ arr: (2)
Add an element to the beginning of the array:
Unshift @ arr, 1; # @ arr: (1, 2, 3)
Add elements to the array:
Push @ arr, (4jue 5); # @ arr: (1pr 2pr 3jre 4pr 5)
Sorting arrays: sort function
Sort by numeric size: @ SORT = sort {$a $b} @ array
Sort in dictionary order: @ SORT = sort {$a cmp $b} @ array
# 1 sorts by default in dictionary order: @ SORT = sort @ array
# 2 sort from small to big by default
# 3 reverse sort: change the positions of $an and $b above
For example:
My @ arr = (2, 14, 14, 3)
My @ arr2 = sort @ arr
Print "@ arr2\ n"; # output: 14 2 3
@ arr2 = sort {$aqb} @ arr
Print "@ arr2\ n"; # output: 2 3 14
Keys and values functions
My% hash = (a = > 1, b = > 2, c = > 3)
My @ key = keys% hash; # @ key:
My @ value = values% hash; # @ value:
Print "keys = @ keys\ nvalues = @ value\ n"
Display:
Keys = c a b
Values = 3 1 2
Defined and exists functions
Defined: returns false if its parameter is not defined, or if the value is undef, otherwise it returns true
Exists: verify whether a key exists in hash, and return true if it exists, false otherwise
My $str
Defined $str; # returns false
$str = 1
Defined $str; # returns true
My% hash= (a = > 1m b = > 2m c = > 3)
Exist $hash {a}; # returns true
Exist $hash {d}; # returns false
$hash {d} = undef
Exist $hash {d}; # returns true
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