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
              sets  unbuffered  writes  to stdout and line buffered reads from
              stdin.  Records from stdin are lines regardless of the value  of
              RS.

       -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                     2026-01-28                           MAWK(1)
