http://www.tutorialspoint.com/unix_commands/awk.htm

NAME

gawk - pattern scanning and processing language

SYNOPSIS

gawk [ POSIX or GNU style options ] -f program-file [ -- ] file ... 
gawk [ POSIX or GNU style options ] [ -- ] program-text file ...

pgawk [ POSIX or GNU style options ] -f program-file [ -- ] file ... 
pgawk [ POSIX or GNU style options ] [ -- ] program-text file ...

DESCRIPTION

Gawk is the GNU Project’s implementation of the AWK programming language. It conforms to the definition of the language in the POSIX 1003.2 Command Language And Utilities Standard. This version in turn is based on the description in The AWK Programming Language, by Aho, Kernighan, and Weinberger, with the additional features found in the System V Release 4 version of UNIX awk. Gawk also provides more recent Bell Laboratories awk extensions, and a number of GNU-specific extensions.

Pgawk is the profiling version of gawk. It is identical in every way to gawk, except that programs run more slowly, and it automatically produces an execution profile in the fileawkprof.out when done. See the --profile option, below.

The command line consists of options to gawk itself, the AWK program text (if not supplied via the -f or --file options), and values to be made available in the ARGC andARGV pre-defined AWK variables.

OPTION FORMAT

Gawk options may be either traditional POSIX one letter options, or GNU style long options. POSIX options start with a single ‘‘-’’, while long options start with ‘‘--’’. Long options are provided for both GNU-specific features and for POSIX-mandated features.

Following the POSIX standard, gawk-specific options are supplied via arguments to the -W option. Multiple -W options may be supplied Each -W option has a corresponding long option, as detailed below. Arguments to long options are either joined with the option by an = sign, with no intervening spaces, or they may be provided in the next command line argument. Long options may be abbreviated, as long as the abbreviation remains unique.

OPTIONS

Gawk accepts the following options, listed alphabetically.

In compatibility mode, any other options are flagged as invalid, but are otherwise ignored. In normal operation, as long as program text has been supplied, unknown options are passed on to the AWK program in the ARGV array for processing. This is particularly useful for running AWK programs via the ‘‘#!’’ executable interpreter mechanism.

AWK PROGRAM EXECUTION

An AWK program consists of a sequence of pattern-action statements and optional function definitions.

pattern { action statements } 
function name(parameter list) { statements }

Gawk first reads the program source from the program-file(s) if specified, from arguments to --source, or from the first non-option argument on the command line. The -f and --source options may be used multiple times on the command line. Gawk reads the program text as if all the program-files and command line source texts had been concatenated together. This is useful for building libraries of AWK functions, without having to include them in each new AWK program that uses them. It also provides the ability to mix library functions with command line programs.

The environment variable AWKPATH specifies a search path to use when finding source files named with the -f option. If this variable does not exist, the default path is".:/usr/local/share/awk". (The actual directory may vary, depending upon how gawkwas built and installed.) If a file name given to the -f option contains a ‘‘/’’ character, no path search is performed.

Gawk executes AWK programs in the following order. First, all variable assignments specified via the -v option are performed. Next, gawk compiles the program into an internal form. Then, gawk executes the code in the BEGIN block(s) (if any), and then proceeds to read each file named in the ARGV array. If there are no files named on the command line, gawk reads the standard input.

If a filename on the command line has the form var=val it is treated as a variable assignment. The variable var will be assigned the value val. (This happens after anyBEGIN block(s) have been run.) Command line variable assignment is most useful for dynamically assigning values to the variables AWK uses to control how input is broken into fields and records. It is also useful for controlling state if multiple passes are needed over a single data file.

If the value of a particular element of ARGV is empty (""), gawk skips over it.

For each record in the input, gawk tests to see if it matches any pattern in the AWKprogram. For each pattern that the record matches, the associated action is executed. The patterns are tested in the order they occur in the program.

Finally, after all the input is exhausted, gawk executes the code in the END block(s) (if any).

VARIABLES, RECORDS AND FIELDS

AWK variables are dynamic; they come into existence when they are first used. Their values are either floating-point numbers or strings, or both, depending upon how they are used. AWK also has one dimensional arrays; arrays with multiple dimensions may be simulated. Several pre-defined variables are set as a program runs; these will be described as needed and summarized below.

Records

Normally, records are separated by newline characters. You can control how records are separated by assigning values to the built-in variable RS. If RS is any single character, that character separates records. Otherwise, RS is a regular expression. Text in the input that matches this regular expression separates the record. However, in compatibility mode, only the first character of its string value is used for separating records. If RS is set to the null string, then records are separated by blank lines. WhenRS is set to the null string, the newline character always acts as a field separator, in addition to whatever value FS may have.

Fields

As each input record is read, gawk splits the record into fields, using the value of the FSvariable as the field separator. If FS is a single character, fields are separated by that character. If FS is the null string, then each individual character becomes a separate field. Otherwise, FS is expected to be a full regular expression. In the special case thatFS is a single space, fields are separated by runs of spaces and/or tabs and/or newlines. (But see the discussion of --posix, below). NOTE: The value of IGNORECASE(see below) also affects how fields are split when FS is a regular expression, and how records are separated when RS is a regular expression.

If the FIELDWIDTHS variable is set to a space separated list of numbers, each field is expected to have fixed width, and gawk splits up the record using the specified widths. The value of FS is ignored. Assigning a new value to FS overrides the use ofFIELDWIDTHS, and restores the default behavior.

Each field in the input record may be referenced by its position, $1, $2, and so on. $0 is the whole record. Fields need not be referenced by constants:

n = 5 
print $n

prints the fifth field in the input record.

The variable NF is set to the total number of fields in the input record.

References to non-existent fields (i.e. fields after $NF) produce the null-string. However, assigning to a non-existent field (e.g., $(NF+2) = 5) increases the value of NF, creates any intervening fields with the null string as their value, and causes the value of $0 to be recomputed, with the fields being separated by the value of OFS. References to negative numbered fields cause a fatal error. Decrementing NF causes the values of fields past the new value to be lost, and the value of $0 to be recomputed, with the fields being separated by the value of OFS.

Assigning a value to an existing field causes the whole record to be rebuilt when $0 is referenced. Similarly, assigning a value to $0 causes the record to be resplit, creating new values for the fields.

Built-in Variables

Gawk’s built-in variables are:

Arrays

Arrays are subscripted with an expression between square brackets ([ and ]). If the expression is an expression list (expr, expr ...) then the array subscript is a string consisting of the concatenation of the (string) value of each expression, separated by the value of the SUBSEP variable. This facility is used to simulate multiply dimensioned arrays. For example:

i = "A"; j = "B"; k = "C" 
x[i, j, k] = "hello, world\n"

assigns the string "hello, world\n" to the element of the array x which is indexed by the string "A\034B\034C". All arrays in AWK are associative, i.e. indexed by string values.

The special operator in may be used in an if or while statement to see if an array has an index consisting of a particular value.

if (val in array)
        print array[val]

If the array has multiple subscripts, use (i, j) in array.

The in construct may also be used in a for loop to iterate over all the elements of an array.

An element may be deleted from an array using the delete statement. The deletestatement may also be used to delete the entire contents of an array, just by specifying the array name without a subscript.

Variable Typing And Conversion

Variables and fields may be (floating point) numbers, or strings, or both. How the value of a variable is interpreted depends upon its context. If used in a numeric expression, it will be treated as a number, if used as a string it will be treated as a string.

To force a variable to be treated as a number, add 0 to it; to force it to be treated as a string, concatenate it with the null string.

When a string must be converted to a number, the conversion is accomplished usingstrtod(3). A number is converted to a string by using the value of CONVFMT as a format string for sprintf(3), with the numeric value of the variable as the argument. However, even though all numbers in AWK are floating-point, integral values are always converted as integers. Thus, given

CONVFMT = "%2.2f"
a = 12
b = a ""

the variable b has a string value of "12" and not "12.00".

Gawk performs comparisons as follows: If two variables are numeric, they are compared numerically. If one value is numeric and the other has a string value that is a ‘‘numeric string,’’ then comparisons are also done numerically. Otherwise, the numeric value is converted to a string and a string comparison is performed. Two strings are compared, of course, as strings. Note that the POSIX standard applies the concept of ‘‘numeric string’’ everywhere, even to string constants. However, this is clearly incorrect, andgawk does not do this. (Fortunately, this is fixed in the next version of the standard.)

Note that string constants, such as "57", are not numeric strings, they are string constants. The idea of ‘‘numeric string’’ only applies to fields, getline input, FILENAME,ARGV elements, ENVIRON elements and the elements of an array created by split()that are numeric strings. The basic idea is that user input, and only user input, that looks numeric, should be treated that way.

Uninitialized variables have the numeric value 0 and the string value "" (the null, or empty, string).

Octal and Hexadecimal Constants

Starting with version 3.1 of gawk , you may use C-style octal and hexadecimal constants in your AWK program source code. For example, the octal value 011 is equal to decimal9, and the hexadecimal value 0x11 is equal to decimal 17.

String Constants

String constants in AWK are sequences of characters enclosed between double quotes ("). Within strings, certain escape sequences are recognized, as in C. These are:

The escape sequences may also be used inside constant regular expressions (e.g., /[ \t\f\n\r\v]/ matches whitespace characters).

In compatibility mode, the characters represented by octal and hexadecimal escape sequences are treated literally when used in regular expression constants. Thus,/a\52b/ is equivalent to /a\*b/.

PATTERNS AND ACTIONS

AWK is a line-oriented language. The pattern comes first, and then the action. Action statements are enclosed in { and }. Either the pattern may be missing, or the action may be missing, but, of course, not both. If the pattern is missing, the action is executed for every single record of input. A missing action is equivalent to

{ print }

which prints the entire record.

Comments begin with the ‘‘#’’ character, and continue until the end of the line. Blank lines may be used to separate statements. Normally, a statement ends with a newline, however, this is not the case for lines ending in a ‘‘,’’, {, ?, :, &&, or ||. Lines ending indo or else also have their statements automatically continued on the following line. In other cases, a line can be continued by ending it with a ‘‘\’’, in which case the newline will be ignored.

Multiple statements may be put on one line by separating them with a ‘‘;’’. This applies to both the statements within the action part of a pattern-action pair (the usual case), and to the pattern-action statements themselves.

Patterns

AWK patterns may be one of the following:

BEGIN 
END 
/regular expression/ 
relational expression 
pattern && pattern 
pattern || pattern 
pattern ? pattern : pattern 
(pattern) 
! pattern 
pattern1, pattern2 

BEGIN and END are two special kinds of patterns which are not tested against the input. The action parts of all BEGIN patterns are merged as if all the statements had been written in a single BEGIN block. They are executed before any of the input is read. Similarly, all the END blocks are merged, and executed when all the input is exhausted (or when an exit statement is executed). BEGIN and END patterns cannot be combined with other patterns in pattern expressions. BEGIN and END patterns cannot have missing action parts.

For /regular expression/ patterns, the associated statement is executed for each input record that matches the regular expression. Regular expressions are the same as those in egrep(1), and are summarized below.

A relational expression may use any of the operators defined below in the section on actions. These generally test whether certain fields match certain regular expressions.

The &&, ||, and ! operators are logical AND, logical OR, and logical NOT, respectively, as in C. They do short-circuit evaluation, also as in C, and are used for combining more primitive pattern expressions. As in most languages, parentheses may be used to change the order of evaluation.

The ?: operator is like the same operator in C. If the first pattern is true then the pattern used for testing is the second pattern, otherwise it is the third. Only one of the second and third patterns is evaluated.

The pattern1, pattern2 form of an expression is called a range pattern. It matches all input records starting with a record that matches pattern1, and continuing until a record that matches pattern2, inclusive. It does not combine with any other sort of pattern expression.

Regular Expressions

Regular expressions are the extended kind found in egrep. They are composed of characters as follows:

The escape sequences that are valid in string constants (see below) are also valid in regular expressions.

Character classes are a new feature introduced in the POSIX standard. A character class is a special notation for describing lists of characters that have a specific attribute, but where the actual characters themselves can vary from country to country and/or from character set to character set. For example, the notion of what is an alphabetic character differs in the USA and in France.

A character class is only valid in a regular expression inside the brackets of a character list. Character classes consist of [:, a keyword denoting the class, and :]. The character classes defined by the POSIX standard are:

For example, before the POSIX standard, to match alphanumeric characters, you would have had to write /[A-Za-z0-9]/. If your character set had other alphabetic characters in it, this would not match them, and if your character set collated differently from ASCII, this might not even match the ASCII alphanumeric characters. With the POSIX character classes, you can write /[[:alnum:]]/, and this matches the alphabetic and numeric characters in your character set.

Two additional special sequences can appear in character lists. These apply to non-ASCII character sets, which can have single symbols (called collating elements) that are represented with more than one character, as well as several characters that are equivalent for collating, or sorting, purposes. (E.g., in French, a plain ‘‘e’’ and a grave-accented e` are equivalent.)

Actions

Action statements are enclosed in braces, { and }. Action statements consist of the usual assignment, conditional, and looping statements found in most languages. The operators, control statements, and input/output statements available are patterned after those in C.

Operators

The operators in AWK, in order of decreasing precedence, are

Control Statements

The control statements are as follows:

if (condition) statement [ else statement ]
while (condition) statement 
do statement while (condition)
for (expr1; expr2; expr3) statement
for (var in array) statement
break
continue
delete array[index]
delete array
exit [ expression ]
{ statements }

I/O Statements

The input/output statements are as follows:

Additional output redirections are allowed for print and printf.

The getline command returns 0 on end of file and -1 on an error. Upon an error, ERRNOcontains a string describing the problem.

NOTE: If using a pipe or co-process to getline, or from print or printf within a loop, youmust use close() to create new instances of the command. AWK does not automatically close pipes or co-processes when they return EOF.

The printf Statement

The AWK versions of the printf statement and sprintf() function (see below) accept the following conversion specification formats:

NOTE: When using the integer format-control letters for values that are outside the range of a C long integer, gawk switches to the %g format specifier. If --lint is provided on the command line gawk warns about this. Other versions of awk may print invalid values or do something else entirely.

Optional, additional parameters may lie between the % and the control letter:

The dynamic width and prec capabilities of the ANSI C printf() routines are supported. A* in place of either the width or prec specifications causes their values to be taken from the argument list to printf or sprintf(). To use a positional specifier with a dynamic width or precision, supply the count$ after the * in the format string. For example,"%3$*2$.*1$s".

Special File Names

When doing I/O redirection from either print or printf into a file, or via getline from a file, gawk recognizes certain special filenames internally. These filenames allow access to open file descriptors inherited from gawk’s parent process (usually the shell). These file names may also be used on the command line to name data files. The filenames are:

These are particularly useful for error messages. For example:

print "You blew it!" > "/dev/stderr"

whereas you would otherwise have to use

print "You blew it!" | "cat 1>&2"

The following special filenames may be used with the |& co-process operator for creating TCP/IP network connections.

Other special filenames provide access to information about the running gawk process.These filenames are now obsolete. Use the PROCINFO array to obtain the information they provide. The filenames are:

Numeric Functions

AWK has the following built-in arithmetic functions:

String Functions

Gawk has the following built-in string functions:

Time Functions

Since one of the primary uses of AWK programs is processing log files that contain time stamp information, gawk provides the following functions for obtaining time stamps and formatting them.

Bit Manipulations Functions

Starting with version 3.1 of gawk, the following bit manipulation functions are available. They work by converting double-precision floating point values to unsigned longintegers, doing the operation, and then converting the result back to floating point. The functions are:

Internationalization Functions

Starting with version 3.1 of gawk, the following functions may be used from within your AWK program for translating strings at run-time. For full details, see GAWK: Effective AWK Programming.

USER-DEFINED FUNCTIONS

Functions in AWK are defined as follows:

function name(parameter list) { statements }

Functions are executed when they are called from within expressions in either patterns or actions. Actual parameters supplied in the function call are used to instantiate the formal parameters declared in the function. Arrays are passed by reference, other variables are passed by value.

Since functions were not originally part of the AWK language, the provision for local variables is rather clumsy: They are declared as extra parameters in the parameter list. The convention is to separate local variables from real parameters by extra spaces in the parameter list. For example:

function  f(p, q,     a, b)     # a and b are local
{
        ...
}

The left parenthesis in a function call is required to immediately follow the function name, without any intervening white space. This is to avoid a syntactic ambiguity with the concatenation operator. This restriction does not apply to the built-in functions listed above.

Functions may call each other and may be recursive. Function parameters used as local variables are initialized to the null string and the number zero upon function invocation.

Use return expr to return a value from a function. The return value is undefined if no value is provided, or if the function returns by ‘‘falling off’’ the end.

If --lint has been provided, gawk warns about calls to undefined functions at parse time, instead of at run time. Calling an undefined function at run time is a fatal error.

The word func may be used in place of function.

DYNAMICALLY LOADING NEW FUNCTIONS

Beginning with version 3.1 of gawk, you can dynamically add new built-in functions to the running gawk interpreter. The full details are beyond the scope of this manual page; see GAWK: Effective AWK Programming for the details.

This function is provided and documented in GAWK: Effective AWK Programming, but everything about this feature is likely to change in the next release. We STRONGLY recommend that you do not use this feature for anything that you aren’t willing to redo.

SIGNALS

pgawk accepts two signals. SIGUSR1 causes it to dump a profile and function call stack to the profile file, which is either awkprof.out, or whatever file was named with the --profile option. It then continues to run. SIGHUP causes it to dump the profile and function call stack and then exit.

EXAMPLES

Print and sort the login names of all users:

INTERNATIONALIZATION

String constants are sequences of characters enclosed in double quotes. In non-English speaking environments, it is possible to mark strings in the AWK program as requiring translation to the native natural language. Such strings are marked in the AWK program with a leading underscore (‘‘_’’). For example,

gawk ’BEGIN { print "hello, world" }’

always prints hello, world. But,

gawk ’BEGIN { print _"hello, world" }’

might print bonjour, monde in France.

There are several steps involved in producing and running a localizable AWK program.

The internationalization features are described in full detail in GAWK: Effective AWK Programming.

POSIX COMPATIBILITY

A primary goal for gawk is compatibility with the POSIX standard, as well as with the latest version of UNIX awk. To this end, gawk incorporates the following user visible features which are not described in the AWK book, but are part of the Bell Laboratories version of awk, and are in the POSIX standard.

The book indicates that command line variable assignment happens when awk would otherwise open the argument as a file, which is after the BEGIN block is executed. However, in earlier implementations, when such an assignment appeared before any file names, the assignment would happen before the BEGIN block was run. Applications came to depend on this ‘‘feature.’’ When awk was changed to match its documentation, the -v option for assigning variables before program execution was added to accommodate applications that depended upon the old behavior. (This feature was agreed upon by both the Bell Laboratories and the GNU developers.)

The -W option for implementation specific features is from the POSIX standard.

When processing arguments, gawk uses the special option ‘‘--’’ to signal the end of arguments. In compatibility mode, it warns about but otherwise ignores undefined options. In normal operation, such arguments are passed on to the AWK program for it to process.

The AWK book does not define the return value of srand(). The POSIX standard has it return the seed it was using, to allow keeping track of random number sequences. Therefore srand() in gawk also returns its current seed.

Other new features are: The use of multiple -f options (from MKS awk); the ENVIRONarray; the \a, and \v escape sequences (done originally in gawk and fed back into the Bell Laboratories version); the tolower() and toupper() built-in functions (from the Bell Laboratories version); and the ANSI C conversion specifications in printf (done first in the Bell Laboratories version).

HISTORICAL FEATURES

There are two features of historical AWK implementations that gawk supports. First, it is possible to call the length() built-in function not only with no argument, but even without parentheses! Thus,

a = length      # Holy Algol 60, Batman!

is the same as either of

a = length() 
a = length($0)

This feature is marked as ‘‘deprecated’’ in the POSIX standard, and gawk issues a warning about its use if --lint is specified on the command line.

The other feature is the use of either the continue or the break statements outside the body of a while, for, or do loop. Traditional AWK implementations have treated such usage as equivalent to the next statement. Gawk supports this usage if --traditionalhas been specified.

GNU EXTENSIONS

Gawk has a number of extensions to POSIX awk. They are described in this section. All the extensions described here can be disabled by invoking gawk with the --traditionaloption.

The following features of gawk are not available in POSIX awk.

The AWK book does not define the return value of the close() function. Gawk’s close()returns the value from fclose(3), or pclose(3), when closing an output file or pipe, respectively. It returns the process’s exit status when closing an input pipe. The return value is -1 if the named file, pipe or co-process was not opened with a redirection.

When gawk is invoked with the --traditional option, if the fs argument to the -F option is ‘‘t’’, then FS is set to the tab character. Note that typing gawk -F\t ... simply causes the shell to quote the ‘‘t,’’, and does not pass ‘‘\t’’ to the -F option. Since this is a rather ugly special case, it is not the default behavior. This behavior also does not occur if --posix has been specified. To really get a tab character as the field separator, it is best to use single quotes: gawk -F’\t’ ....

If gawk is configured with the --enable-switch option to the configure command, then it accepts an additional control-flow statement:

switch (expression) {
case value|regex : statement
...
[ default: statement ]
}

ENVIRONMENT VARIABLES

The AWKPATH environment variable can be used to provide a list of directories thatgawk searches when looking for files named via the -f and --file options.

If POSIXLY_CORRECT exists in the environment, then gawk behaves exactly as if --posix had been specified on the command line. If --lint has been specified, gawk issues a warning message to this effect.

SEE ALSO

getpid(2), getppid(2), getpgrp(2), getuid(2), geteuid(2), getgid(2), getegid(2),getgroups(2)

The AWK Programming Language, Alfred V. Aho, Brian W. Kernighan, Peter J. Weinberger, Addison-Wesley, 1988. ISBN 0-201-07981-X.

GAWK: Effective AWK Programming, Edition 3.0, published by the Free Software Foundation, 2001.

BUGS

The -F option is not necessary given the command line variable assignment feature; it remains only for backwards compatibility.

Syntactically invalid single character programs tend to overflow the parse stack, generating a rather unhelpful message. Such programs are surprisingly difficult to diagnose in the completely general case, and the effort to do so really is not worth it.

AUTHORS

The original version of UNIX awk was designed and implemented by Alfred Aho, Peter Weinberger, and Brian Kernighan of Bell Laboratories. Brian Kernighan continues to maintain and enhance it.

Paul Rubin and Jay Fenlason, of the Free Software Foundation, wrote gawk, to be compatible with the original version of awk distributed in Seventh Edition UNIX. John Woods contributed a number of bug fixes. David Trueman, with contributions from Arnold Robbins, made gawk compatible with the new version of UNIX awk. Arnold Robbins is the current maintainer.

The initial DOS port was done by Conrad Kwok and Scott Garfinkle. Scott Deifik is the current DOS maintainer. Pat Rankin did the port to VMS, and Michal Jaegermann did the port to the Atari ST. The port to OS/2 was done by Kai Uwe Rommel, with contributions and help from Darrel Hankerson. Fred Fish supplied support for the Amiga, Stephen Davies provided the Tandem port, and Martin Brown provided the BeOS port.

VERSION INFORMATION

This man page documents gawk, version 3.1.5.

BUG REPORTS

If you find a bug in gawk, please send electronic mail to bug-gawk@gnu.org. Please include your operating system and its revision, the version of gawk (from gawk --version), what C compiler you used to compile it, and a test program and data that are as small as possible for reproducing the problem.

Before sending a bug report, please do two things. First, verify that you have the latest version of gawk. Many bugs (usually subtle ones) are fixed at each release, and if yours is out of date, the problem may already have been solved. Second, please read this man page and the reference manual carefully to be sure that what you think is a bug really is, instead of just a quirk in the language.

Whatever you do, do NOT post a bug report in comp.lang.awk. While the gawkdevelopers occasionally read this newsgroup, posting bug reports there is an unreliable way to report bugs. Instead, please use the electronic mail addresses given above.

If you’re using a GNU/Linux system or BSD-based system, you may wish to submit a bug report to the vendor of your distribution. That’s fine, but please send a copy to the official email address as well, since there’s no guarantee that the bug will be forwarded to the gawk maintainer.

ACKNOWLEDGEMENTS

Brian Kernighan of Bell Laboratories provided valuable assistance during testing and debugging. We thank him.

COPYING PERMISSIONS

Copyright ? 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002, 2003, 2004, 2005 Free Software Foundation, Inc.

Permission is granted to make and distribute verbatim copies of this manual page provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual page under the conditions for verbatim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual page into another language, under the above conditions for modified versions, except that this permission notice may be stated in a translation approved by the Foundation. 

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