MAWK-CODE(7) Miscellaneous MAWK-CODE(7)

mawk-code - dumping mawk's byte-code

At startup, mawk compiles the script into byte-code. After that, it interprets the compiled byte-code. Use the -Wdump option to show the byte-code.

As mawk executes the program, it maintains a reference to the command to execute in cdp. After that there may be data and/or references in cdp[0], cdp[1], etc.

When an operation requires operands, mawk pushes the values (or array/string references) onto the stack, which updates the stack pointer sp. When the operation completes, mawk consumes those entries on the stack, pushing the result (if any) onto the stack.

While executing user-defined functions, mawk maintains a frame pointer fp to address the function's local variables.

Concatenate array-indices.

Usage:

Forms a multiple array index by concatenating the elements of sp[1-cnt..0], with each element separated by SUBSEP.

Parameters:


cnt, the number of elements to concatenate follows the command.
hold reference to the elements to concatenate.
Returns the index in sp[0].

Delete an array item.

Usage:

delete array[expr]

Parameters:

points to array
is an expr

Find the length of an array.

Usage:

length(array)

Parameters:

points to array.

Returns the length of the array in sp[0].

Push array address onto stack.

Usage:

This is used to set up a calling argument for a function.

Parameters:

array reference follows the command.

Returns the array in sp[0].

Test if an expression is present in an array.

Usage:

(expression in array)

Parameters:

points to an array.
is an expression.

Returns 1 in sp[0] if the expression is found, 0 otherwise.

Add two numbers.

Usage:

first + second

Parameters:

holds the second value.
holds the first value.

Returns the sum in sp[0].

Combined addition/assignment.

Usage:

target += source

Parameters:

is the source expression
points to the target

Stores the sum in the target, leaving sp[0] pointing to the target.

Push reference to array cell, given expression for its index.

Usage:

arrayname[expression]

Parameters:

an array reference follows the command.
has an expression, used for the index of a cell in the array.

Returns a reference to the addressed cell in sp[0].

Push contents of array cell, given expression for its index.

Usage:

arrayname[expression]

Parameters:

has an expression, used for the index of a cell in the array.

Returns contents of the addressed cell in sp[0].

Update reference to next cell for array loop.

Usage:

for ( i in arrayname ) statement

Parameters:

Mawk maintains a stack of array-loop state. It updates the array/cell references in the current loop's state.

Assigns a value.

Usage:

target = source

Parameters:

is the source expression
points to the target

Stores the sum in the target, leaving sp[0] pointing to the target.

Compute arc-tangent of two values.

Usage:

atan2( first, second )

Parameters:

holds the second value
holds the first value

Returns the result in sp[0].

Call a function.

Usage:

function()

Parameters:

is a reference to the function block
holds number of input arguments

Returns function value in sp[0].

Concatenate two strings.

Usage:

first second

Parameters:

is the second string.
is the first string.

Returns the result in sp[0].

Close the file or pipe associated with an expression.

Usage:

close( expression )

Parameters:

holds the expression identifying the file to close

Returns the status from closing the file, 0 on success or -1 on failure.

Compute the cosine of a value in radians.

Usage:

cos( value )

Parameters:

is the value.

Returns the result in sp[0].

Delete an array.

Usage:

delete(array)

Parameters:

is the array to delete.

Divide one number by another.

Usage:

first / second

Parameters:

is the second value.
is the first value.

Returns the quotient in sp[0].

Combined division/assignment.

Usage:

target /= source

Parameters:

is the source
points to the target

Stores the quotient in the target, leaving sp[0] pointing to the target.

Compare two values.

Usage:

first == second

Parameters:

is the second value
is the first value

Returns 1 in sp[0] if the values are equal, otherwise 0.

Exits mawk with a specific exit-code.

Usage:

exit(exit_code)

Parameters:

is the exit_code

Exits mawk with success

Usage:

exit

Parameters:

none

Compute base-e exponential function of a value.

Usage:

exp( value )

Parameters:

is the value

Returns the result in sp[0].

Combination addition/assignment to NF.

Usage:

NF += expression

Parameters:

is the expression to add

Assign an expression to NF.

Usage:

NF = expression

Parameters:

is the expression

Combination division/assignment to NF.

Usage:

NF /= expression

Parameters:

is the expression

Combination modulus/assignment to NF.

Usage:

NF %= expression

Parameters:

is the expression

Combination multiplication/assignment to NF.

Usage:

NF *= expression

Parameters:

is the expression

Post-decrement using NF.

Usage:

NF--

Parameters:

holds a reference to the field to use

Post-increment using NF.

Usage:

NF++

Parameters:

holds a reference to the field to use

Exponentiation using NF.

Usage:

NF ^= expression

Parameters:

is the expression to use

Predecrement using NF.

Usage:

--NF

Parameters:

holds a reference to the field to use

Preincrement using NF.

Usage:

++NF

Parameters:

holds a reference to the field to use

Push array reference to data split-up as fields..

Usage:

$0 = expression
getline

Parameters:

is a reference to the data to be split/assigned.

Returns the resulting array reference in sp[0].

Push contents of numbered field.

Usage:

$expression

Parameters:

holds a reference to $expression
holds expression

Returns the field's value in sp[0].

Combination subtraction/assignment to NF.

Usage:

NF -= expression

Parameters:

holds a reference to the field to use

Push reference to numbered field.

Usage:

$number

Parameters:

holds the field number

Returns a reference to the field in sp[0].

Push content of numbered field.

Usage:

$number

Parameters:

holds the field number

Returns the field's content in sp[0].

Flush the output file or pipe associated with an expression.

Usage:

fflush( expression )

Parameters:

is the expression value

Returns the result in sp[0].

Test if first value is greater than the second.

Usage:

first > second

Parameters:

holds the second value.
holds the first value.

Returns 1 in sp[0] if the first value is greater than, otherwise 0.

Test if first value is greater than or equal to the second.

Usage:

first >= second

Parameters:

holds the second value.
holds the first value.

Returns 1 in sp[0] if the first value is greater than or equal, otherwise 0.

Find the position of the second string in the first.

Usage:

index( first, second )

Parameters:

is the second string
is the first string

Returns the position in sp[0] starting at 1 if found, 0 if not found.

Returns a value truncated towards zero..

Usage:

int( value )

Parameters:

is the value

Returns the result in sp[0].

Go from BEGIN code to MAIN code.

Usage:

(internal state)

Parameters:

Jump to a new byte-code position, by a given number of bytes.

Usage:

(internal state)

Parameters:

holds the (signed) number of bytes by which to jump.

Jump to a new byte-code position if sp[0] is nonzero, by a given number of bytes.

Usage:

(internal state)

Parameters:


holds the (signed) number of bytes by which to jump.

holds a value to compare against 0.

Jump to a new byte-code position if sp[0] is zero, by a given number of bytes.

Usage:

(internal state)

Parameters:


holds the (signed) number of bytes by which to jump.

holds a value to compare against 0.

Push a local address onto the evaluation stack.

Usage:

(internal state)

Parameters:


holds the offset from the frame pointer fp.

Returns the address in sp[0].

Push contents of a local variable onto the evaluation stack.

Usage:

(internal state)

Parameters:


holds the offset from the frame pointer fp.

Returns the contents of the local variable in sp[0].

Pushes a reference to an array onto the evaluation stack.

Usage:

arrayname

Parameters:


holds the offset from the frame pointer fp of a reference to an array.

Returns a reference to the array in sp[0].

Pushes a reference to a given array cell onto the evaluation stack.

Usage:

arrayname[expression]

Parameters:


holds the offset from the frame pointer fp of a reference to an array.

holds an expression

Returns a reference to the specified array cell in sp[0].

Pushes the contents of a given array cell onto the evaluation stack.

Usage:

arrayname[expression]

Parameters:


holds the offset from the frame pointer fp of a reference to an array.

holds an expression

Returns the contents of the specified array cell in sp[0].

Returns the length of a string or array value.

Usage:

length( value )

Parameters:

is the string or array reference

Returns the length in sp[0].

Special jump for logical-OR, always preceded by test.

Usage:

(internal state)

Parameters:


holds the (signed) number of bytes by which to jump if the value is nonzero.

holds a value to compare against 0.

Special jump for logical-OR, always preceded by test.

Usage:

(internal state)

Parameters:


holds the (signed) number of bytes by which to jump if the value is zero.

holds a value to compare against 0.

Compute the natural logarithm of a value.

Usage:

log( value )

Parameters:

is the value

Returns the result in sp[0].

Test if first value is less than the second.

Usage:

first < second

Parameters:

holds the second value.
holds the first value.

Returns 1 in sp[0] if the first value is less than, otherwise 0.

Test if first value is less than or equal to the second.

Usage:

first <= second

Parameters:

holds the second value.
holds the first value.

Returns 1 in sp[0] if the first value is less than or equal, otherwise 0.

Test if $0 matches a given regular expression.

Usage:

$0 ~ regex

Parameters:


holds a reference to a regular expression.

Returns 1 in sp[0] if $0 matches the regular expression, 0 otherwise.

Test if a given expression matches a given regular expression.

Usage:

expression ~ regex

Parameters:


holds a reference to a regular expression.

holds an expression to test.

Returns 1 in sp[0] if the expression matches the regular expression, 0 otherwise.

Test if an expression in sp[-1] matches the regular expression in sp[0].

Usage:

expression ~ regex

Parameters:


holds a reference to a regular expression.

holds an expression to test.

Returns 1 in sp[0] if the expression matches the regular expression, 0 otherwise.

Converts a date specification in systime format to a timestamp.

Usage:

mktime( string )

Parameters:

holds the date-specification string

Returns the result in sp[0].

Compute modulus/remainder with two operands.

Usage:

first % second

Parameters:

holds the second operand
holds the first operand

Returns the remainder in sp[0].

Assign modulus/remainder with two operands.

Usage:

first %= second

Parameters:

holds the second operand
holds the first operand

Returns the remainder in sp[0] as well as replacing the first value.

Compute product with two operands.

Usage:

first * second

Parameters:

holds the second value
holds the first value

Returns the product in sp[0].

Assign product with two operands.

Usage:

first *= second

Parameters:

holds the second value
holds the first value

Returns the product in sp[0] as well as replacing the first value.

Compare two values.

Usage:

first != second

Parameters:

is the second value
is the first value

Returns 1 in sp[0] if the values are not equal, otherwise 0.

Read the next record, restart pattern testing.

Usage:

next

Parameters:

Begin processing the next file listed on the command line.

Usage:

nextfile

Parameters:

Push the number of fields (NF) onto the evaluation stack.

Usage:

(internal state)

Parameters:

Compute a logical negation.

Usage:

! value

Parameters:

holds a value to negate.

Returns the result on the evaluation stack, i.e., 0 if the value is nonzero and 1 otherwise.

Read into $0 using getline.

Usage:

getline

Parameters:

Read into $0 using getline, updating NR and FNR.

Usage:

getline < file

Parameters:

Start executing the main section of the script (between BEGIN and END).

Usage:

(internal state)

Parameters:

Pop the evaluation stack, discarding the value.

Usage:

(internal state)

Parameters:

Finish an array “in” loop, deallocating the state information.

Usage:

(internal state)

Parameters:

Post-decrement a value.

Usage:

value --

Parameters:

holds the value to decrement

Returns the updated value in sp[0].

Post-increment a value.

Usage:

value ++

Parameters:

holds the value to increment

Returns the updated value in sp[0].

Compute the first value raised to the power of the second value.

Usage:

first ^ second

Parameters:

holds the second value
holds the first value

Returns the result in sp[0].

Assign the first value raised to the power of the second value.

Usage:

variable = first ^ second

Parameters:

is a reference to the variable which will be assigned the result
holds the second value
holds the first value

Pre-decrement a value.

Usage:

-- value

Parameters:

holds the value to decrement.

Returns the updated value in sp[0];.

Pre-increment a value.

Usage:

++ value

Parameters:

holds the value to decrement.

Returns the updated value in sp[0];.

Push array address onto stack.

Usage:

(internal state)

Parameters:

array reference follows the command.

Returns the array in sp[0].

Push a data cell onto the evaluation stack.

Usage:

(internal state)

Parameters:

is a reference to the data to push

Returns a reference to the result in sp[0].

Push a double floating value onto the evaluation stack.

Usage:

(internal state)

Parameters:

is a reference to the data to push

Returns a reference to the result in sp[0].

Push contents of next referenced variable onto the evaluation stack.

Usage:

(internal state)

Parameters:

is a reference to the data cell to copy.

Returns a reference to the result in sp[0].

Reserve the next slot on the evaluation stack, setting its type.

Usage:

(internal state)

Parameters:

holds the type to set in the new slot, e.g., for data via I/O redirection

Returns a reference to the result in sp[0].

Push a reference to a string value onto the evaluation stack.

Usage:

(internal state)

Parameters:

holds a reference to the string value

Returns a reference to the result in sp[0].

Returns a random number between zero and one..

Usage:

rand()

Parameters:

Returns the result in sp[0].

Test a range pattern: pat1, pat2 { action }.

Usage:

(internal state)

Parameters:

a flag, test pat1 if on else pat2
offset of pat2 code from cdp
offset of action code from cdp
offset of code after the action from cdp
start of pat1 code
holds arguments for the action.

Return a function value.

Usage:

return value

Parameters:

holds the return value

When calling a function, mawk saves the current stack, creating a new one. On return, mawk restores the previous stack and returns the function value in sp[0].

Return from a function without providing a return-value.

Usage:

return

Parameters:

is modified to make the value uninitialized.

As in the ret operation, mawk restores the previous stack. After the return, sp[0] is an uninitialized value.

Begin an array “in” loop.

Usage:

for ( iterator in arrayname ) statement

Parameters:

holds a reference to the array
holds a reference to the iteration variable

Mawk pushes a new entry onto the array loop stack, and updates cdp to point to the statement to execute.

Compute the sine of a value in radians.

Usage:

sin( value )

Parameters:

holds the value

Returns the result in sp[0].

Returns a string constructed from expression-list according to format.

Usage:

sprintf( format [, value1 [,... ] ] )

Parameters:

is the last parameter value; there can be up to 255.
Returns the resulting string in sp[0].

Returns the square root of a value.

Usage:

sqrt( value 0

Parameters:

is the value

Returns the result in sp[0].

Seeds the random number generator.

Usage:

srand( value )
srand( )

Parameters:

is the seed value, which may be uninitialized

Returns the previous seed value in sp[0].

Finish a range pattern.

Usage:

(internal state)

Parameters:

Formats the given timestamp using the given format.

Usage:

strftime( format , timestamp , utc )
strftime( format , timestamp )
strftime( format )
strftime( )

Parameters:

Zero to three parameters may be on the stack. If all three are used, they are as follows:

is the utc flag
is the timestamp value
is the format

Returns the result in sp[0].

Subtract the second value from the first.

Usage:

first - second

Parameters:

holds the second value
holds the first value

Returns the result in sp[0].

Assign the difference of two values to a variable.

Usage:

target = first - second

Parameters:

holds a reference to the variable to which to assign the result
holds the second value
holds the first value

Stores the difference in the target, leaving sp[0] pointing to the target.

eturns the substring of string s, starting at index i, of length n.

Usage:

substr(s,i,n)
substr(s,i)

Parameters:

Two or three parameters may be on the stack. If all three are used, they are as follows:

holds the length n.
holds the index i.
holds the string s.

Executes a command, returning the wait-status.

Usage:

status = system( command )

Parameters:

is the command to execute

Returns the wait-status in sp[0].

Returns the current time of day as the number of seconds since the Epoch.

Usage:

systime( )

Parameters:

Returns the result in sp[0].

Test a logical expression.

Usage:

value

Parameters:

holds a value to test.

Returns the result on the evaluation stack, i.e., 1 if the value is nonzero and 0 otherwise.

Copy a string, converting to lowercase.

Usage:

tolower( value )

Parameters:

is the value to convert

Returns the result in sp[0].

Copy a string, converting to uppercase.

Usage:

toupper( value )

Parameters:

is the value to convert

Returns the result in sp[0].

Unitary minus.

Usage:

- value

Parameters:

contains a value to negate. As a side-effect, if the value is a string, it is cast to double floating point.

Returns the result in sp[0].

Unitary plus.

Usage:

+ value

Parameters:

contains a value to use. As a side-effect, if the value is a string, it is cast to double floating point.

Returns the result in sp[0].

mandatory jump

optional (undesirable) jump

optional (desirable) jump

pop pos'n, optional jump if advanced

end of match

arbitrary character (.)

character class

end of string ($)

push position onto stack

start of string (^)

matching a literal string

arbitrary string (.*)

2024-01-23 Version 1.3.4