MAWK(1)                          User commands                         MAWK(1)

NAME
       mawk - pattern scanning and text processing language

SYNOPSIS
       mawk  [-W  option]  [-F value] [-v var=value] [--] 'program text' [file
       ...]
       mawk [-W option] [-F value] [-v var=value] [-f program-file] [--] [file
       ...]

DESCRIPTION
       mawk is an interpreter for  the  AWK  Programming  Language.   The  AWK
       language  is  useful for manipulation of data files, text retrieval and
       processing, and for  prototyping  and  experimenting  with  algorithms.
       mawk  is a new awk meaning it implements the AWK language as defined in
       Aho, Kernighan and Weinberger, The AWK Programming  Language,  Addison-
       Wesley  Publishing, 1988 (hereafter referred to as the AWK book.)  mawk
       conforms to the  POSIX  1003.2  (draft  11.3)  definition  of  the  AWK
       language  which  contains a few features not described in the AWK book,
       and mawk provides a small number of extensions.

       An AWK program is a sequence of pattern  {action}  pairs  and  function
       definitions.   Short  programs  are entered on the command line usually
       enclosed in ' ' to avoid shell interpretation.  Longer programs can  be
       read  in  from a file with the -f option.  Data  input is read from the
       list of files on the command line or from standard input when the  list
       is empty.  The input is broken into records as determined by the record
       separator   variable,  RS.   Initially,  RS  =  "\n"  and  records  are
       synonymous with lines.  Each record is compared  against  each  pattern
       and if it matches, the program text for {action} is executed.

OPTIONS
       -F value       sets the field separator, FS, to value.

       -f file        Program  text  is  read  from  file  instead of from the
                      command line.  Multiple -f options are allowed.

       -v var=value   assigns value to program variable var.

       --             indicates the unambiguous end of options.

       The  above  options  will  be  available  with  any  POSIX   compatible
       implementation  of  AWK.   Implementation specific options are prefaced
       with -W.  mawk provides these:

       -W dump
              writes an assembler like listing of the internal  representation
              of   the   program   to   stdout  and  exits  0  (on  successful
              compilation).

       -W exec file
              Program text is read from file and this is the last option.

              This is a useful alternative to -f on systems that  support  the
              #!   "magic  number"  convention  for executable scripts.  Those
              implicitly pass the pathname of the script itself as  the  final
              parameter,  and  expect  no  more  than one "-" option on the #!
              line.  Because mawk can combine multiple -W options separated by
              commas, you can use this option when an additional -W option  is
              needed.

       -W help
              prints a usage message to stderr and exits (same as "-W usage").

       -W interactive
              changes  the  buffering  of  stdout  and  stdin  to make it more
              responsive in interactive use.

              Normally mawk does not change the  standard  streams  buffering,
              which uses line-buffering stdin and stdout if they are connected
              to  a  terminal, and block-buffering otherwise (e.g., if mawk is
              run in a pipe).

              When opening a pipe, a special file (such as "-"), or one of the
              stdio devices, mawk first opens a file  descriptor.   Mawk  then
              decides  whether  to  use  buffered  I/O by checking if the file
              descriptor is for a terminal, and if RS is currently set to  the
              single  character  "\n"  (newline).   As  a  special  case, file
              descriptor zero (0) is assigned to stdin, while  fdopen  handles
              other file descriptors.

              The  interactive  option bypasses both checks in deciding to use
              buffered I/O (is a terminal, and RS is "\n").   The  interactive
              option also changes stdout to unbuffered (like stderr).

              Mawk changes streams to unbuffered I/O in a few other cases:

              o   if a file is created or appended to, i.e., using ">" or ">>"
                  mawk  treats  this  differently  from  opening  pipes, first
                  opening it as a stream (block buffered) and then changing it
                  to unbuffered if it happens to be a terminal.

              o   if the standard output is connected to a  terminal  and  the
                  the  interactive  option  was  not given, mawk changes it to
                  unbuffered.

       -W posix
              modifies mawk's behavior to be more POSIX-compliant:

              o   forces mawk not to consider '\n' to be space.

                  The original "posix_space" is recognized, but deprecated.

              o   Allow  hexadecimal,  "inf"  (infinity)  and  "nan"   (not-a-
                  number).

                  The  Open  Group Base Specifications Issue 8 allows but does
                  not require these features.

       -W random=num
              calls srand with the given parameter (and  overrides  the  auto-
              seeding behavior).

       -W sprintf=num
              adjusts the size of mawk's internal sprintf buffer to num bytes.
              More  than  rare  use  of  this  option indicates mawk should be
              recompiled.

       -W traditional
              Omit features  such  as  interval  expressions  which  were  not
              supported by traditional awk.

       -W usage
              prints a usage message to stderr and exits (same as "-W help").

       -W version
              mawk  writes  its  version  and copyright to stdout and compiled
              limits to stderr and exits 0.

       mawk accepts abbreviations for any of these options, e.g.,  "-W v"  and
       "-Wv" both tell mawk to show its version.

       mawk  allows  multiple  -W  options  to  be  combined by separating the
       options with commas, e.g., -Wsprint=2000,posix.   This  is  useful  for
       executable #!  "magic number" invocations in which only one argument is
       supported, e.g., -Winteractive,exec.

THE AWK LANGUAGE
   1. Program structure
       An  AWK  program  is  a  sequence  of  pattern  {action} pairs and user
       function definitions.

       A pattern can be:
            BEGIN
            END
            expression
            expression , expression

       One, but not both, of pattern {action} can be omitted.  If {action}  is
       omitted  it is implicitly { print }.  If pattern is omitted, then it is
       implicitly matched.  BEGIN and END patterns require an action.

       Statements are terminated by newlines, semi-colons or both.  Groups  of
       statements such as actions or loop bodies are blocked via { ... } as in
       C.   The  last  statement  in a block doesn't need a terminator.  Blank
       lines have no meaning; an empty statement is terminated  with  a  semi-
       colon.   Long  statements  can  be  continued  with  a backslash, \.  A
       statement can be broken without a backslash after a comma, left  brace,
       &&,  ||,  do,  else,  the  right  parenthesis  of  an  if, while or for
       statement, and the right  parenthesis  of  a  function  definition.   A
       comment  starts  with # and extends to, but does not include the end of
       line.

       The following statements control program flow inside blocks.

            if ( expr ) statement

            if ( expr ) statement else statement

            while ( expr ) statement

            do statement while ( expr )

            for ( opt_expr ; opt_expr ; opt_expr ) statement

            for ( var in array ) statement

            continue

            break

   2. Data types, conversion and comparison
       There are two basic data types, numeric and string.  Numeric  constants
       can  be  integer  like -2, decimal like 1.08, or in scientific notation
       like -1.1e4 or .28E-3.  All numbers are represented internally and  all
       computations  are  done  in floating point arithmetic.  So for example,
       the expression 0.2e2 == 20 is true and true is represented as 1.0.

       String constants are enclosed in double quotes.

                   "This is a string with a newline at the end.\n"

       Strings can be continued across a line by  escaping  (\)  the  newline.
       The following escape sequences are recognized.

            \\        \
            \"        "
            \a        alert, ascii 7
            \b        backspace, ascii 8
            \t        tab, ascii 9
            \n        newline, ascii 10
            \v        vertical tab, ascii 11
            \f        formfeed, ascii 12
            \r        carriage return, ascii 13
            \ddd      1, 2 or 3 octal digits for ascii ddd
            \xhh      1 or 2 hex digits for ascii  hh

       If  you  escape  any other character \c, you get \c, i.e., mawk ignores
       the escape.

       There are really three basic data types; the third is number and string
       which has both a numeric value and a string value  at  the  same  time.
       User  defined  variables  come into existence when first referenced and
       are initialized to null, a number and string value  which  has  numeric
       value  0 and string value "".  Non-trivial number and string typed data
       come from input and are typically stored in fields.  (See section 4).

       The type of an expression is determined by its  context  and  automatic
       type  conversion  occurs  if  needed.   For  example,  to  evaluate the
       statements

            y = x + 2  ;  z = x  "hello"

       The value stored in variable y will be typed  numeric.   If  x  is  not
       numeric,  the  value  read  from x is converted to numeric before it is
       added to 2 and stored in y.  The value stored in  variable  z  will  be
       typed  string,  and  the  value  of  x  will  be converted to string if
       necessary and concatenated with "hello".  (Of  course,  the  value  and
       type  stored  in  x  is  not  changed  by  any  conversions.)  A string
       expression is converted to numeric using its longest numeric prefix  as
       with atof(3).  A numeric expression is converted to string by replacing
       expr with sprintf(CONVFMT, expr), unless expr can be represented on the
       host  machine as an exact integer then it is converted to sprintf("%d",
       expr).  Sprintf() is an AWK built-in that duplicates the  functionality
       of  sprintf(3),  and  CONVFMT  is a built-in variable used for internal
       conversion from number to string and initialized to  "%.6g".   Explicit
       type  conversions  can  be  forced,  expr  ""  is  string and expr+0 is
       numeric.

       To evaluate, expr1 rel-op expr2, if both operands are numeric or number
       and string then the comparison is numeric; if both operands are  string
       the  comparison  is  string;  if  one operand is string, the non-string
       operand is converted and the  comparison  is  string.   The  result  is
       numeric, 1 or 0.

       In boolean contexts such as, if ( expr ) statement, a string expression
       evaluates  true  if  and only if it is not the empty string ""; numeric
       values if and only if not numerically zero.

   3. Regular expressions
       In the AWK language, records, fields and strings are often  tested  for
       matching  a  regular  expression.   Regular expressions are enclosed in
       slashes, and

            expr ~ /r/

       is an AWK expression that evaluates to 1 if  expr  "matches"  r,  which
       means  a substring of expr is in the set of strings defined by r.  With
       no match the expression evaluates to  0;  replacing  ~  with  the  "not
       match" operator, !~ , reverses the meaning.  As  pattern-action pairs,

            /r/ { action }   and   $0 ~ /r/ { action }

       are  the  same,  and  for  each  input record that matches r, action is
       executed.  In fact, /r/ is an AWK expression that is equivalent to  ($0
       ~  /r/)  anywhere  except when on the right side of a match operator or
       passed as an argument to a built-in function  that  expects  a  regular
       expression argument.

       AWK uses extended regular expressions as with the -E option of grep(1).
       The regular expression metacharacters, i.e., those with special meaning
       in regular expressions are

            \ ^ $ . [ ] | ( ) * + ? { }

       If the command line option -W traditional is used, these are omitted:

            { }

       are  also  regular expression metacharacters, and in this mode, require
       escaping to be a literal character.

       Regular expressions are built up from characters as follows:

            c            matches any non-metacharacter c.

            \c           matches  a  character  defined  by  the  same  escape
                         sequences  used  in  string  constants or the literal
                         character c if \c is not an escape sequence.

            .            matches any character (including newline).

            ^            matches the front of a string.

            $            matches the back of a string.

            [c1c2c3...]  matches any character in the  class  c1c2c3... .   An
                         interval  of  characters  is  denoted  c1-c2 inside a
                         class [...].

            [^c1c2c3...] matches any character not in the class c1c2c3...

       Regular expressions are built up  from  other  regular  expressions  as
       follows:

            r1r2         matches     r1    followed    immediately    by    r2
                         (concatenation).


            r1 | r2      matches r1 or r2 (alternation).


            r*           matches r repeated zero or more times.

            r+           matches r repeated one or more times.

            r?           matches r zero or once.  (repetition).

            (r)          matches r (grouping).


            r{n}         matches r exactly n times.

            r{n,}        matches r repeated n or more times.

            r{n,m}       matches r repeated n to m (inclusive) times.

            r{,m}        matches r repeated  0  to  m  times  (a  non-standard
                         option).

       The increasing precedence of operators is:

       alternation concatenation repetition grouping


       For example,

            /^[_a-zA-Z][_a-zA-Z0-9]*$/  and
            /^[-+]?([0-9]+\.?|\.[0-9])[0-9]*([eE][-+]?[0-9]+)?$/

       are  matched by AWK identifiers and AWK numeric constants respectively.
       Note that "." has to be escaped to be recognized as  a  decimal  point,
       and that metacharacters are not special inside character classes.

       Any  expression  can  be  used  on  the  right hand side of the ~ or !~
       operators or passed to a built-in that expects  a  regular  expression.
       If needed, it is converted to string, and then interpreted as a regular
       expression.  For example,

            BEGIN { identifier = "[_a-zA-Z][_a-zA-Z0-9]*" }

            $0 ~ "^" identifier

       prints all lines that start with an AWK identifier.

       mawk  recognizes  the  empty  regular expression, //, which matches the
       empty string and hence is matched by any string at the front, back  and
       between every character.  For example,

            echo  abc | mawk '{ gsub(//, "X")' ; print }
            XaXbXcX


   4. Records and fields
       Records are read in one at a time, and stored in the field variable $0.
       The  record  is split into fields which are stored in $1, $2, ..., $NF.
       The built-in variable NF is set to the number of fields, and NR and FNR
       are incremented by 1.  Fields above $NF are set to "".

       Assignment to $0 causes the fields and NF to be recomputed.  Assignment
       to NF or to a field causes $0 to be reconstructed by concatenating  the
       $i's  separated  by OFS.  Assignment to a field with index greater than
       NF, increases NF and causes $0 to be reconstructed.

       Data input stored in fields is string,  unless  the  entire  field  has
       numeric form and then the type is number and string.  For example,

            echo 24 24E |
            mawk '{ print($1>100, $1>"100", $2>100, $2>"100") }'
            0 1 1 1

       $0 and $2 are string and $1 is number and string.  The first comparison
       is numeric, the second is string, the third is string (100 is converted
       to "100"), and the last is string.

   5. Expressions and operators
       The expression syntax is similar to C.  Primary expressions are numeric
       constants,  string  constants,  variables,  fields, arrays and function
       calls.  The identifier for a variable,  array  or  function  can  be  a
       sequence of letters, digits and underscores, that does not start with a
       digit.   Variables  are  not declared; they exist when first referenced
       and are initialized to null.

       New expressions are composed with the following operators in  order  of
       increasing precedence.

            assignment          =  +=  -=  *=  /=  %=  ^=
            conditional         ?  :
            logical or          ||
            logical and         &&
            array membership    in
            matching       ~   !~
            relational          <  >   <=  >=  ==  !=
            concatenation       (no explicit operator)
            add ops             +  -
            mul ops             *  /  %
            unary               +  -
            logical not         !
            exponentiation      ^
            inc and dec         ++ -- (both post and pre)
            field               $

       Assignment, conditional and exponentiation associate right to left; the
       other  operators  associate  left  to  right.   Any  expression  can be
       parenthesized.

   6. Arrays
       Awk provides one-dimensional arrays.  Array elements are  expressed  as
       array[expr].   Expr  is  internally  converted  to string type, so, for
       example, A[1] and A["1"] are the same element and the actual  index  is
       "1".    Arrays  indexed  by  strings  are  called  associative  arrays.
       Initially an array is empty; elements exist when  first  accessed.   An
       expression, expr in array evaluates to 1 if array[expr] exists, else to
       0.

       There  is  a form of the for statement that loops over each index of an
       array.

            for ( var in array ) statement

       sets var to each index of array and executes statement.  The order that
       var transverses the indices of array is not defined.

       The statement, delete array[expr], causes  array[expr]  not  to  exist.
       mawk  supports  the delete array feature, which deletes all elements of
       array.

       Multidimensional arrays are synthesized with  concatenation  using  the
       built-in   variable   SUBSEP.    array[expr1,expr2]  is  equivalent  to
       array[expr1 SUBSEP expr2].  Testing for a multidimensional element uses
       a parenthesized index, such as

            if ( (i, j) in A )  print A[i, j]


   7. Builtin-variables
       The following variables are built-in  and  initialized  before  program
       execution.

            ARGC   number of command line arguments.

            ARGV   array of command line arguments, 0..ARGC-1.

            CONVFMT
                   format  for  internal  conversion  of  numbers  to  string,
                   initially = "%.6g".

            ENVIRON
                   array indexed by  environment  variables.   An  environment
                   string, var=value is stored as ENVIRON[var] = value.

            FILENAME
                   name of the current input file.

            FNR    current record number in FILENAME.

            FS     splits records into fields as a regular expression.

            NF     number of fields in the current record.

            NR     current record number in the total input stream.

            OFMT   format for printing numbers; initially = "%.6g".

            OFS    inserted between fields on output, initially = " ".

            ORS    terminates each record on output, initially = "\n".

            RLENGTH
                   length  set  by  the  last  call  to the built-in function,
                   match().

            RS     input record separator, initially = "\n".

            RSTART index set by the last call to match().

            SUBSEP used  to  build  multiple  array  subscripts,  initially  =
                   "\034".

   8. Built-in functions
       String functions

            gsub(r,s,t)  gsub(r,s)
                   Global substitution, every match of regular expression r in
                   variable  t  is  replaced  by  string  s.   The  number  of
                   replacements is returned.  If t is omitted, $0 is used.  An
                   & in the replacement string s is replaced  by  the  matched
                   substring   of  t.   \&  and  \\  put   literal  &  and  \,
                   respectively, in the replacement string.

            index(s,t)
                   If t is a substring of s, then the position where t  starts
                   is  returned, else 0 is returned.  The first character of s
                   is in position 1.

            length(s)
                   Returns the length of string or array s.

            match(s,r)
                   Returns the index of the first  longest  match  of  regular
                   expression  r  in  string  s.  Returns 0 if no match.  As a
                   side effect, RSTART is set to the return value.  RLENGTH is
                   set to the length of the match or -1 if no match.   If  the
                   empty  string  is  matched,  RLENGTH  is set to 0, and 1 is
                   returned if the match is at the front, and  length(s)+1  is
                   returned if the match is at the back.

            split(s,A,r)  split(s,A)
                   String  s  is split into fields by regular expression r and
                   the fields are loaded into array A.  The number  of  fields
                   is  returned.   See section 11 below for more detail.  If r
                   is omitted, FS is used.

            sprintf(format,expr-list)
                   Returns a string constructed from  expr-list  according  to
                   format.  See the description of printf() below.

            sub(r,s,t)  sub(r,s)
                   Single  substitution,  same  as  gsub()  except at most one
                   substitution.

            substr(s,i,n)  substr(s,i)
                   Returns the substring of string s, starting at index i,  of
                   length  n.  If n is omitted, the suffix of s, starting at i
                   is returned.

            tolower(s)
                   Returns  a  copy  of  s  with  all  upper  case  characters
                   converted to lower case.

            toupper(s)
                   Returns  a  copy  of  s  with  all  lower  case  characters
                   converted to upper case.

       Time functions

       These are available on systems which support the corresponding C mktime
       and strftime functions:

            mktime(specification)
                   converts a date specification to a timestamp with the  same
                   units  as  systime.   The  date  specification  is a string
                   containing the components of the date as decimal integers:

                   YYYY
                      the year, e.g., 2012

                   MM the month of the year starting at 1

                   DD the day of the month starting at 1

                   HH hour (0-23)

                   MM minute (0-59)

                   SS seconds (0-59)

                   DST
                      tells how to  treat  timezone  versus  daylight  savings
                      time:

                        positive
                           DST is in effect

                        zero (default)
                           DST is not in effect

                        negative
                           mktime()   should  (use  timezone  information  and
                           system databases to) attempt  to determine  whether
                           DST is in effect at the specified time.

            strftime([format [, timestamp [, utc ]]])
                   formats the given timestamp using the format (passed to the
                   C strftime function):

                   o   If the format parameter is missing, "%c" is used.

                   o   If  the  timestamp  parameter  is  missing, the current
                       value from systime is used.

                   o   If the utc parameter is present and nonzero, the result
                       is in UTC.  Otherwise local time is used.

            systime()
                   returns the current time of day as the  number  of  seconds
                   since the Epoch (1970-01-01 00:00:00 UTC on POSIX systems).

       Arithmetic functions

            atan2(y,x)
                   Arctan of y/x between -pi and pi.

            cos(x) Cosine function, x in radians.

            exp(x) Exponential function.

            int(x) Returns x truncated towards zero.

            log(x) Natural logarithm.

            rand() Returns a random number between zero and one.

            sin(x) Sine function, x in radians.

            sqrt(x)
                   Returns square root of x.

            srand(expr)

            srand()
                   Seeds  the random number generator, using the clock if expr
                   is omitted, and returns the value  of  the  previous  seed.
                   Srand(expr)   is   useful   for   repeating  pseudo  random
                   sequences.

                   Note: mawk is normally configured to seed the random number
                   generator from the clock at startup, making it  unnecessary
                   to  call  srand().   This  feature  can  be  suppressed via
                   conditional  compile,  or  overridden  using  the  -Wrandom
                   option.

   9. Input and output
       There are two output statements, print and printf.

            print  writes $0  ORS to standard output.

            print expr1, expr2, ..., exprn
                   writes  expr1  OFS  expr2  OFS  ...  exprn  ORS to standard
                   output.  Numeric expressions are converted to  string  with
                   OFMT.

            printf format, expr-list
                   duplicates   the  printf  C  library  function  writing  to
                   standard output.  The complete ANSI C format specifications
                   are recognized with conversions %c, %d, %e, %E, %f, %g, %G,
                   %i, %o, %s, %u, %x, %X and %%, and conversion qualifiers  h
                   and l.

       The  argument  list  to  print  or printf can optionally be enclosed in
       parentheses.  Print formats  numbers  using  OFMT  or  "%d"  for  exact
       integers.   "%c" with a numeric argument prints the corresponding 8 bit
       character, with a string argument it prints the first character of  the
       string.   The output of print and printf can be redirected to a file or
       command by appending > file, >> file or | command to  the  end  of  the
       print   statement.   Redirection  opens  file  or  command  only  once,
       subsequent  redirections  append  to  the  already  open  stream.    By
       convention, mawk associates the filename

          o   "/dev/stderr" with stderr,

          o   "/dev/stdout" with stdout,

          o   "-" and "/dev/stdin" with stdin.

       The  association  with  stderr  is  especially useful because it allows
       print and printf to be redirected to stderr.  These names can  also  be
       passed to functions.

       The input function getline has the following variations.

            getline
                   reads into $0, updates the fields, NF, NR and FNR.

            getline < file
                   reads into $0 from file, updates the fields and NF.

            getline var
                   reads the next record into var, updates NR and FNR.

            getline var < file
                   reads the next record of file into var.

            command | getline
                   pipes  a record from command into $0 and updates the fields
                   and NF.

            command | getline var
                   pipes a record from command into var.

       Getline returns 0 on end-of-file, -1 on error, otherwise 1.

       Commands on the end of pipes are executed by /bin/sh.

       The function close(expr) closes the file or pipe associated with  expr.
       Close  returns  0 if expr is an open file, the exit status if expr is a
       piped command, and -1 otherwise.  Close is used to  reread  a  file  or
       command,  make  sure  the  other  end  of an output pipe is finished or
       conserve file resources.

       The function fflush(expr) flushes the output file  or  pipe  associated
       with  expr.  Fflush returns 0 if expr is an open output stream else -1.
       Fflush without an  argument  flushes  stdout.   Fflush  with  an  empty
       argument ("") flushes all open output.

       The  function  system(expr)  uses  the C runtime system call to execute
       expr and returns the  corresponding  wait  status  of  the  command  as
       follows:

       o   if  the  system call failed, setting the status to -1, mawk returns
           that value.

       o   if the command exited normally, mawk returns its exit-status.

       o   if the command exited due to a signal such as SIGHUP, mawk  returns
           the signal number plus 256.

       Changes  made  to the ENVIRON array are not passed to commands executed
       with system or pipes.

   10. User defined functions
       The syntax for a user defined function is

            function name( args ) { statements }

       The function body can contain a return statement

            return opt_expr

       A return statement is not required.  Function calls may  be  nested  or
       recursive.   Functions  are  passed  expressions by value and arrays by
       reference.   Extra  arguments  serve  as  local   variables   and   are
       initialized to null.  For example, csplit(s,A) puts each character of s
       into array A and returns the length of s.

            function csplit(s, A,    n, i)
            {
              n = length(s)
              for( i = 1 ; i <= n ; i++ ) A[i] = substr(s, i, 1)
              return n
            }

       Putting  extra  space  between  passed arguments and local variables is
       conventional.  Functions can be referenced before they are defined, but
       the function name and the '(' of the  arguments  must  touch  to  avoid
       confusion with concatenation.

       A function parameter is normally a scalar value (number or string).  If
       there  is  a  forward  reference  to  a  function  using  an array as a
       parameter, the function's corresponding parameter will be treated as an
       array.

   11. Splitting strings, records and files
       Awk programs use the same algorithm to split strings into  arrays  with
       split(), and records into fields on FS.  mawk uses essentially the same
       algorithm to split files into records on RS.

       Split(expr,A,sep) works as follows:

          (1)  If  sep  is  omitted,  it  is  replaced  by  FS.  Sep can be an
               expression or regular expression.  If it is  an  expression  of
               non-string type, it is converted to string.

          (2)  If sep = " " (a single space), then <SPACE> is trimmed from the
               front  and back of expr, and sep becomes <SPACE>.  mawk defines
               <SPACE> as the regular expression /[ \t\n]+/.  Otherwise sep is
               treated as a regular expression,  except  that  meta-characters
               are  ignored  for  a string of length 1, e.g., split(x, A, "*")
               and split(x, A, /\*/) are the same.

          (3)  If expr is not string, it is converted to string.  If  expr  is
               then the empty string "", split() returns 0 and A is set empty.
               Otherwise, all non-overlapping, non-null and longest matches of
               sep in expr, separate expr into fields which are loaded into A.
               The  fields  are  placed  in  A[1], A[2], ..., A[n] and split()
               returns n, the number of fields which is the number of  matches
               plus  one.  Data placed in A that looks numeric is typed number
               and string.

       Splitting records into fields works the  same  except  the  pieces  are
       loaded into $1, $2,..., $NF.  If $0 is empty, NF is set to 0 and all $i
       to "".

       mawk  splits  files  into  records  by the same algorithm, but with the
       slight  difference  that  RS  is  really  a  terminator  instead  of  a
       separator.  (ORS is really a terminator too).

            E.g., if FS = ":+" and $0 = "a::b:" , then NF = 3 and $1 = "a", $2
            = "b" and $3 = "", but if "a::b:" is the contents of an input file
            and RS = ":+", then there are two records "a" and "b".

       RS = " " is not special.

       If  FS  =  "",  then mawk breaks the record into individual characters,
       and, similarly, split(s,A,"") places the  individual  characters  of  s
       into A.

   12. Multi-line records
       Since  mawk  interprets  RS as a regular expression, multi-line records
       are easy.  Setting RS = "\n\n+", makes one or more blank lines separate
       records.  If FS = " " (the default), then single newlines, by the rules
       for  <SPACE>  above,  become  space  and  single  newlines  are   field
       separators.

            For example, if

            o   a file is "a b\nc\n\n",

            o   RS = "\n\n+" and

            o   FS = " ",

            then  there  is one record "a b\nc" with three fields "a", "b" and
            "c":

            o   using FS = "\n", gives two fields "a b" and "c";

            o   using FS = "", gives one field identical to the record.

       If you want lines with spaces or tabs to be considered blank, set RS  =
       "\n([ \t]*\n)+".   For  compatibility  with other awks, setting RS = ""
       has the same effect as if blank lines are stripped from the  front  and
       back  of  files  and  then  records  are determined as if RS = "\n\n+".
       POSIX requires  that  "\n"  always  separates  records  when  RS  =  ""
       regardless  of the value of FS.  mawk does not support this convention,
       because defining "\n" as <SPACE> makes it unnecessary.

       Most of the time when you change RS for multi-line  records,  you  will
       also want to change ORS to "\n\n" so the record spacing is preserved on
       output.

   13. Program execution
       This  section  describes the order of program execution.  First ARGC is
       set to the total  number  of  command  line  arguments  passed  to  the
       execution phase of the program.

       o   ARGV[0] is set to the name of the AWK interpreter and

       o   ARGV[1]   ...    ARGV[ARGC-1]  holds  the  remaining  command  line
           arguments exclusive of options and program source.

       For example, with

            mawk  -f  prog  v=1  A  t=hello  B

       ARGC = 5 with
              ARGV[0] = "mawk",
              ARGV[1] = "v=1",
              ARGV[2] = "A",
              ARGV[3] = "t=hello" and
              ARGV[4] = "B".

       Next, each BEGIN block is executed in order.  If the  program  consists
       entirely  of  BEGIN  blocks,  then  execution terminates, else an input
       stream is opened and execution continues.  If ARGC equals 1, the  input
       stream  is  set  to stdin, else  the command line arguments ARGV[1] ...
       ARGV[ARGC-1] are examined for a file argument.

       The command line arguments divide  into  three  sets:  file  arguments,
       assignment  arguments and empty strings "".  An assignment has the form
       var=string.  When an ARGV[i] is examined as a possible  file  argument,
       if  it  is  empty  it  is skipped; if it is an assignment argument, the
       assignment to var takes place and i skips to the  next  argument;  else
       ARGV[i] is opened for input.  If it fails to open, execution terminates
       with exit code 2.  If no command line argument is a file argument, then
       input comes from stdin.  Getline in a BEGIN action opens input.  "-" as
       a file argument denotes stdin.

       Once  an input stream is open, each input record is tested against each
       pattern, and if it matches, the  associated  action  is  executed.   An
       expression  pattern  matches  if  it  is  boolean  true (see the end of
       section 2).  A BEGIN pattern matches before any input  has  been  read,
       and  an  END  pattern  matches  after all input has been read.  A range
       pattern, expr1,expr2 , matches every record between the match of  expr1
       and the match expr2 inclusively.

       When end of file occurs on the input stream, the remaining command line
       arguments  are  examined for a file argument, and if there is one it is
       opened, else the END pattern is considered matched and all END  actions
       are executed.

       In  the example, the assignment v=1 takes place after the BEGIN actions
       are executed, and the data placed in v  is  typed  number  and  string.
       Input  is  then  read  from  file A.  On end of file A, t is set to the
       string "hello", and B is opened for input.  On end of file B,  the  END
       actions are executed.

       Program flow at the pattern {action} level can be changed with the

            next
            nextfile
            exit  opt_expr

       statements:

       o   A  next  statement  causes  the  next  input  record to be read and
           pattern testing to restart with the first pattern {action} pair  in
           the program.

       o   A  nextfile  statement  tells  mawk  to stop processing the current
           input file.  It then updates FILENAME to the next  file  listed  on
           the command line, and resets FNR to 1.

       o   An  exit statement causes immediate execution of the END actions or
           program termination if there are none or if the exit occurs  in  an
           END action.  The opt_expr sets the exit value of the program unless
           overridden by a later exit or subsequent error.

ENVIRONMENT
       Mawk recognizes these variables:

          MAWKBINMODE
             (see COMPATIBILITY)

          MAWK_LONG_OPTIONS
             If  this  is  set,  mawk uses its value to decide what to do with
             GNU-style long options:

               allow  Mawk allows the option to be checked against the (small)
                      set of long options it recognizes.

                      The long names from the -W option are recognized,  e.g.,
                      --version is derived from -Wversion.

               error  Mawk  prints  an  error  message and exits.  This is the
                      default.

               ignore Mawk ignores the option, unless it happens to be one  of
                      the one it recognizes.

               warn   Print  an  warning  message  and  otherwise  ignore  the
                      option.

             If the variable is unset, mawk prints an error message and exits.

          WHINY_USERS
             This is a gawk 3.1.0 feature, removed in the 4.0.0  release.   It
             tells mawk to sort array indices before it starts to iterate over
             the elements of an array.

COMPATIBILITY
   MAWK 1.3.3 versus POSIX 1003.2 Draft 11.3
       The  POSIX  1003.2(draft 11.3) definition of the AWK language is AWK as
       described in the AWK book  with  a  few  extensions  that  appeared  in
       SystemVR4 nawk.  The extensions are:

          o   New functions: toupper() and tolower().

          o   New variables: ENVIRON[] and CONVFMT.

          o   ANSI C conversion specifications for printf() and sprintf().

          o   New  command  options:   -v  var=value,  multiple -f options and
              implementation options as arguments to -W.

          o   For  systems  (MS-DOS  or  Windows)  which  provide  a   setmode
              function,  an  environment  variable  MAWKBINMODE and a built-in
              variable BINMODE.  The bits of the BINMODE value tell mawk   how
              to modify the RS and ORS variables:

              0  set standard input to binary mode, and if BIT-2 is unset, set
                 RS to "\r\n" (CR/LF) rather than "\n" (LF).

              1  set  standard  output  to binary mode, and if BIT-2 is unset,
                 set ORS to "\r\n" (CR/LF) rather than "\n" (LF).

              2  suppress the assignment to RS and ORS  of  CR/LF,  making  it
                 possible  to  run scripts and generate output compatible with
                 Unix line-endings.

       POSIX AWK is oriented to operate on files a line at a time.  RS can  be
       changed  from  "\n" to another single character, but it is hard to find
       any use for this --  there  are  no  examples  in  the  AWK  book.   By
       convention,  RS  =  "", makes one or more blank lines separate records,
       allowing multi-line records.  When RS = "",  "\n"  is  always  a  field
       separator regardless of the value in FS.

       mawk,  on  the  other hand, allows RS to be a regular expression.  When
       "\n" appears in  records,  it  is  treated  as  space,  and  FS  always
       determines fields.

       Removing the line at a time paradigm can make some programs simpler and
       can  often  improve  performance.   For example, redoing example 3 from
       above,

            BEGIN { RS = "[^A-Za-z]+" }

            { word[ $0 ] = "" }

            END { delete  word[ "" ]
              for( i in word )  cnt++
              print cnt
            }

       counts the number of unique words by making each  word  a  record.   On
       moderate  size  files,  mawk  executes  twice  as  fast, because of the
       simplified inner loop.

       The following program replaces each comment by a single space  in  a  C
       program file,

            BEGIN {
              RS = "/\*([^*]|\*+[^/*])*\*+/"
                 # comment is record separator
              ORS = " "
              getline  hold
              }

              { print hold ; hold = $0 }

              END { printf "%s" , hold }

       Buffering  one  record  is  needed to avoid terminating the last record
       with a space.

       With mawk, the following are all equivalent,

            x ~ /a\+b/    x ~ "a\+b"     x ~ "a\\+b"

       The strings get scanned twice, once  as  string  and  once  as  regular
       expression.   On the string scan, mawk ignores the escape on non-escape
       characters while the AWK book advocates \c be  recognized  as  c  which
       necessitates  the double escaping of meta-characters in strings.  POSIX
       explicitly declines to  define  the  behavior  which  passively  forces
       programs that must run under a variety of awks to use the more portable
       but less readable, double escape.

       POSIX  AWK  does  not  recognize  "/dev/std{in,out,err}".  Some systems
       provide an actual device for this, allowing AWKs which do not implement
       the feature directly to support it.

       POSIX AWK does not  recognize  \x  hex  escape  sequences  in  strings.
       Unlike  ANSI C, mawk limits the number of digits that follows \x to two
       as the current implementation only supports 8 bit characters.

       POSIX explicitly leaves the behavior of FS = "" undefined, and mentions
       splitting the record into characters as a possible interpretation,  but
       currently this use is not portable across implementations.

       Some  features  were  not  part  of the POSIX standard until long after
       their introduction in  mawk  and  other  implementations.   These  were
       published in IEEE 1003.1-2024 (The Open Group Base Specifications Issue
       8):

       o   The  built-in  fflush first appeared in a 1993 AT&T awk released to
           netlib.  It was approved for the POSIX standard in 2012.

       o   The built-in nextfile first appeared in gawk in 1988,  was  adopted
           by BWK in 1996, and by mawk in 2012.  It was approved for the POSIX
           standard in 2012.

       o   Aggregate deletion with delete array was approved in 2018.

   Random numbers
       POSIX  does  not  prescribe a method for initializing random numbers at
       startup.

       In practice, most implementations do nothing special, which makes srand
       and rand follow the C runtime library, making the initial seed value 1.
       Some implementations (Solaris XPG4 and Tru64) return 0 from  the  first
       call  to srand, although the results from rand behave as if the initial
       seed is 1.  Other implementations return 1.

       While mawk can call srand at startup with  no  parameter  (initializing
       random  numbers  from  the clock), this feature may be suppressed using
       conditional compilation.

   Extensions added for compatibility for GAWK and BWK
       Mktime, strftime and systime are gawk extensions.

       The  "/dev/stdin"  feature  was  added  to  mawk   after   1.3.4,   for
       compatibility  with gawk and BWK awk.  The corresponding "-" (alias for
       /dev/stdin) was present in mawk 1.3.3.

       Interval  expressions,  e.g.,  a  range  {m,n}  in   Extended   Regular
       Expressions  (EREs),  were  not  supported in awk (or even the original
       "nawk"):

       o   Gawk provided this feature in 1991 (and later, in 1998, options for
           turning it off, for compatibility with "traditional awk").

       o   Interval expressions, were introduced into awk regular  expressions
           in  IEEE  1003.1-2001  (also  known  as  Unix  03), along with some
           internationalization features.

       o   Apple modified its copy of the original awk in April  2006,  making
           this version of awk support interval expressions.

           The  updated  source provides for compatibility with older "legacy"
           versions using an environment variable,  making  this  "Unix  2003"
           feature (perhaps meant as Unix 03) the default.

       o   NetBSD  developers copied this change in January 2018, omitting the
           compatibility option, and then applied it to BWK awk.

       o   The interval expression implementation in mawk is based on  changes
           proposed by James Parkinson in April 2016.

       Mawk  also  recognizes  a  few  gawk-specific  command line options for
       script compatibility:

            --help, --posix, -r, --re-interval, --traditional, --version

   Subtle Differences not in POSIX or the AWK Book
       Finally, here is how mawk handles exceptional cases  not  discussed  in
       the  AWK  book  or the POSIX draft.  It is unsafe to assume consistency
       across awks and safe to skip to the next section.

          o   substr(s, i, n) returns the characters of s in the  intersection
              of the closed interval [1, length(s)] and the half-open interval
              [i,  i+n).  When this intersection is empty, the empty string is
              returned; so substr("ABC", 1, 0) = "" and substr("ABC", -4, 6) =
              "A".

          o   Every string, including the  empty  string,  matches  the  empty
              string  at  the  front so, s ~ // and s ~ "", are always 1 as is
              match(s, //) and match(s, "").  The last two set RLENGTH to 0.

          o   index(s, t) is always the same as match(s, t1) where t1  is  the
              same  as  t with metacharacters escaped.  Hence consistency with
              match requires that index(s, "") always  returns  1.   Also  the
              condition,  index(s,t)  !=  0 if and only t is a substring of s,
              requires index("","") = 1.

          o   If getline encounters end  of  file,  getline  var,  leaves  var
              unchanged.   Similarly,  on  entry  to  the END actions, $0, the
              fields and NF have their value unaltered from the last record.

BUGS
       mawk implements printf() and sprintf() using the C  library  functions,
       printf  and  sprintf,  so  full  ANSI  compatibility requires an ANSI C
       library.  In practice this means the h conversion qualifier may not  be
       available.

       Also mawk inherits any bugs or limitations of the library functions.

       Implementors  of  the  AWK  language  have  shown  a consistent lack of
       imagination when naming their programs.

EXAMPLES
       1. emulate cat.

            { print }

       2. emulate wc.

            { chars += length($0) + 1  # add one for the \n
              words += NF
            }

            END{ print NR, words, chars }

       3. count the number of unique "real words".

            BEGIN { FS = "[^A-Za-z]+" }

            { for(i = 1 ; i <= NF ; i++)  word[$i] = "" }

            END { delete word[""]
                  for ( i in word )  cnt++
                  print cnt
            }

       4. sum the second field of every record based on the first field.

            $1 ~ /credit|gain/ { sum += $2 }
            $1 ~ /debit|loss/  { sum -= $2 }

            END { print sum }

       5. sort a file, comparing as string

            { line[NR] = $0 "" }  # make sure of comparison type
                            # in case some lines look numeric

            END {  isort(line, NR)
              for(i = 1 ; i <= NR ; i++) print line[i]
            }

            #insertion sort of A[1..n]
            function isort( A, n,    i, j, hold)
            {
              for( i = 2 ; i <= n ; i++)
              {
                hold = A[j = i]
                while ( A[j-1] > hold )
                { j-- ; A[j+1] = A[j] }
                A[j] = hold
              }
              # sentinel A[0] = "" will be created if needed
            }


AUTHORS
       Mike Brennan (brennan@whidbey.com).
       Thomas E. Dickey <dickey@invisible-island.net>.

SEE ALSO
       grep(1)

       Aho, Kernighan and Weinberger, The AWK Programming  Language,  Addison-
       Wesley  Publishing, 1988, (the AWK book), defines the language, opening
       with a tutorial and advancing to many interesting programs  that  delve
       into  issues of software design and analysis relevant to programming in
       any language.

       The GAWK Manual, The Free Software Foundation, 1991, is a tutorial  and
       language  reference that does not attempt the depth of the AWK book and
       assumes the reader may be a novice  programmer.   The  section  on  AWK
       arrays is excellent.  It also discusses POSIX requirements for AWK.

       mawk-arrays(7) discusses mawk's implementation of arrays.

       mawk-code(7) gives more information on the -W dump option.

       awk - pattern scanning and processing language
       The Open Group Base Specifications Issue 8
       IEEE Std 1003.1-2024
       https://pubs.opengroup.org/onlinepubs/9799919799/utilities/awk.html

Version 1.3.4                     2026-03-02                           MAWK(1)
