AWK(1)                                                     AWK(1)

     NAME
          awk - pattern-directed scanning and processing language

     SYNOPSIS
          awk [ -F fs ] [ -d ] [ -mf n ] [ -mr n ] [ -safe ] [ -v
          var=value ] [ -f progfile | prog ] [ file ... ]

     DESCRIPTION
          Awk scans each input file for lines that match any of a set
          of patterns specified literally in prog or in one or more
          files specified as -f progfile. With each pattern there can
          be an associated action that will be performed when a line
          of a file matches the pattern.  Each line is matched against
          the pattern portion of every pattern-action statement; the
          associated action is performed for each matched pattern.
          The file name `-' means the standard input.  Any file of the
          form var=value is treated as an assignment, not a file name,
          and is executed at the time it would have been opened if it
          were a file name.  The option -v followed by var=value is an
          assignment to be done before the program is executed; any
          number of -v options may be present.  -F fs option defines
          the input field separator to be the regular expression fs.

          An input line is normally made up of fields separated by
          white space, or by regular expression FS.  The fields are
          denoted $1, $2, ..., while $0 refers to the entire line.  If
          FS is null, the input line is split into one field per char-
          acter.

          To compensate for inadequate implementation of storage man-
          agement, the -mr option can be used to set the maximum size
          of the input record, and the -mf option to set the maximum
          number of fields.

          The -safe option causes awk to run in ``safe mode,'' in
          which it is not allowed to run shell commands or open files
          and the environment is not made available in the ENVIRON
          variable.

          A pattern-action statement has the form

               pattern { action }

          A missing { action } means print the line; a missing pattern
          always matches.  Pattern-action statements are separated by
          newlines or semicolons.

          An action is a sequence of statements.  A statement can be
          one of the following:

     AWK(1)                                                     AWK(1)

          if( expression ) statement [ else statement ]
          while( expression ) statement
          for( expression ; expression ; expression ) statement
          for( var in array ) statement
          do statement while( expression )
          break
          continue
          { [ statement ... ] }
          expression              # commonly var = expression
          print [ expression-list ] [ > expression ]
          printf format [ , expression-list ] [ > expression ]
          return [ expression ]
          next                    # skip remaining patterns on this input line
          nextfile                # skip rest of this file, open next, start at top
          delete array[ expression ]# delete an array element
          delete array            # delete all elements of array
          exit [ expression ]     # exit immediately; status is expression

          Statements are terminated by semicolons, newlines or right
          braces.  An empty expression-list stands for $0.  String
          constants are quoted " ", with the usual C escapes recog-
          nized within.  Expressions take on string or numeric values
          as appropriate, and are built using the operators + - * / %
          ^ (exponentiation), and concatenation (indicated by white
          space).  The operators ! ++ -- += -= *= /= %= ^= > >= < <=
          == != ?: are also available in expressions.  Variables may
          be scalars, array elements (denoted x[i]) or fields.  Vari-
          ables are initialized to the null string.  Array subscripts
          may be any string, not necessarily numeric; this allows for
          a form of associative memory.  Multiple subscripts such as
          [i,j,k] are permitted; the constituents are concatenated,
          separated by the value of SUBSEP.

          The print statement prints its arguments on the standard
          output (or on a file if >file or >>file is present or on a
          pipe if |cmd is present), separated by the current output
          field separator, and terminated by the output record separa-
          tor.  file and cmd may be literal names or parenthesized
          expressions; identical string values in different statements
          denote the same open file.  The printf statement formats its
          expression list according to the format (see fprintf(2)).
          The built-in function close(expr) closes the file or pipe
          expr. The built-in function fflush(expr) flushes any buf-
          fered output for the file or pipe expr. If expr is omitted
          or is a null string, all open files are flushed.

          The mathematical functions exp, log, sqrt, sin, cos, and
          atan2 are built in.  Other built-in functions:

          length  If its argument is a string, the string's length is
                  returned.  If its argument is an array, the number
                  of subscripts in the array is returned.  If no

     AWK(1)                                                     AWK(1)

                  argument, the length of $0 is returned.
          rand    random number on (0,1)
          srand   sets seed for rand and returns the previous seed.
          int     truncates to an integer value
          utf     converts its numerical argument, a character number,
                  to a UTF string
          substr(s, m, n)
                  the n-character substring of s that begins at posi-
                  tion m counted from 1.  If n is omitted, it is taken
                  to be the length of s from m.
          index(s, t)
                  the position in s where the string t occurs, or 0 if
                  it does not.
          match(s, r)
                  the position in s where the regular expression r
                  occurs, or 0 if it does not.  The variables RSTART
                  and RLENGTH are set to the position and length of
                  the matched string.
          split(s, a, fs)
                  splits the string s into array elements a[1], a[2],
                  ..., a[n], and returns n. The separation is done
                  with the regular expression fs or with the field
                  separator FS if fs is not given.  An empty string as
                  field separator splits the string into one array
                  element per character.
          sub(r, t, s)
                  substitutes t for the first occurrence of the regu-
                  lar expression r in the string s. If s is not given,
                  $0 is used.  A `&' character in t will be replaced
                  by the sub-string of s matched by r; it may be
                  escaped with `\' to substitute a literal `&'.
          gsub    same as sub except that all occurrences of the regu-
                  lar expression are replaced; sub and gsub return the
                  number of replacements.
          sprintf(fmt, expr, ...)
                  the string resulting from formatting expr ...
                  according to the printf format fmt
          system(cmd)
                  executes cmd and returns its exit status
          tolower(str)
                  returns a copy of str with all upper-case characters
                  translated to their corresponding lower-case equiva-
                  lents.
          toupper(str)
                  returns a copy of str with all lower-case characters
                  translated to their corresponding upper-case equiva-
                  lents.

          The ``function'' getline sets $0 to the next input record
          from the current input file; getline <file sets $0 to the
          next record from file. getline x sets variable x instead.
          Finally, cmd | getline pipes the output of cmd into getline;

     AWK(1)                                                     AWK(1)

          each call of getline returns the next line of output from
          cmd. In all cases, getline returns 1 for a successful input,
          0 for end of file, and -1 for an error.

          Patterns are arbitrary Boolean combinations (with ! || &&)
          of regular expressions and relational expressions.  Regular
          expressions are as in regexp(6). Isolated regular expres-
          sions in a pattern apply to the entire line.  Regular
          expressions may also occur in relational expressions, using
          the operators ~ and !~.  /re/ is a constant regular expres-
          sion; any string (constant or variable) may be used as a
          regular expression, except in the position of an isolated
          regular expression in a pattern.

          A pattern may consist of two patterns separated by a comma;
          in this case, the action is performed for all lines from an
          occurrence of the first pattern though an occurrence of the
          second.

          A relational expression is one of the following:

               expression matchop regular-expression
               expression relop expression
               expression in array-name
               (expr,expr,...) in array-name

          where a relop is any of the six relational operators in C,
          and a matchop is either ~ (matches) or !~ (does not match).
          A conditional is an arithmetic expression, a relational
          expression, or a Boolean combination of these.

          The special patterns BEGIN and END may be used to capture
          control before the first input line is read and after the
          last.  BEGIN and END do not combine with other patterns.

          Variable names with special meanings:

          CONVFMT   conversion format used when converting numbers
                    (default %.6g)
          FS        regular expression used to separate fields; also
                    settable by option -Ffs.
          NF        number of fields in the current record
          NR        ordinal number of the current record
          FNR       ordinal number of the current record in the cur-
                    rent file
          FILENAME  the name of the current input file
          RS        input record separator (default newline)
          OFS       output field separator (default blank)
          ORS       output record separator (default newline)
          OFMT      output format for numbers (default %.6g)
          SUBSEP    separates multiple subscripts (default 034)
          ARGC      argument count, assignable

     AWK(1)                                                     AWK(1)

          ARGV      argument array, assignable; non-null members are
                    taken as file names
          ENVIRON   array of environment variables; subscripts are
                    names.

          Functions may be defined (at the position of a pattern-
          action statement) thus:

               function foo(a, b, c) { ...; return x }

          Parameters are passed by value if scalar and by reference if
          array name; functions may be called recursively.  Parameters
          are local to the function; all other variables are global.
          Thus local variables may be created by providing excess
          parameters in the function definition.

     EXAMPLES
          length($0) > 72
               Print lines longer than 72 characters.

          { print $2, $1 }
               Print first two fields in opposite order.

          BEGIN { FS = ",[ \t]*|[ \t]+" }
                { print $2, $1 }
               Same, with input fields separated by comma and/or
               blanks and tabs.

               { s += $1 }
          END  { print "sum is", s, " average is", s/NR }
               Add up first column, print sum and average.

          /start/, /stop/
               Print all lines between start/stop pairs.

          BEGIN     {    # Simulate echo(1)
               for (i = 1; i < ARGC; i++) printf "%s ", ARGV[i]
               printf "\n"
               exit }

     SOURCE
          /sys/src/cmd/awk

     SEE ALSO
          sed(1), regexp(6),
          A. V. Aho, B. W. Kernighan, P. J. Weinberger, The AWK Pro-
          gramming Language, Addison-Wesley, 1988.  ISBN 0-201-07981-X

     BUGS
          There are no explicit conversions between numbers and
          strings.  To force an expression to be treated as a number
          add 0 to it; to force it to be treated as a string

     AWK(1)                                                     AWK(1)

          concatenate "" to it.
          The scope rules for variables in functions are a botch; the
          syntax is worse.
          UTF is not always dealt with correctly, though awk does make
          an attempt to do so.  The split function with an empty
          string as final argument now copes with UTF in the string
          being split.