Sprite 1984 - 1993/Sprite 1984 - 1993.iso/man/cmds.fmt/nawk.man

Text File | 1989-01-05 | 11.5 KB | 331 lines

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NNAAMMEE
     awk - pattern-directed scanning and processing language

SSYYNNOOPPSSIISS
     aawwkk [ --FF_f_s ] [ prog ] [ file ... ]

DDEESSCCRRIIPPTTIIOONN
     _A_w_k scans each input _f_i_l_e for lines that match any of a set
     of patterns specified literally in _p_r_o_g or in a file speci-
     fied as --ff _f_i_l_e.  With each pattern there can be an associ-
     ated action that will be performed when a line of a _f_i_l_e
     matches the pattern.  Each line is matched against the pat-
     tern portion of every pattern-action statement; the associ-
     ated action is performed for each matched pattern.  The file
     name means the standard input.  Any _f_i_l_e of the form
     _v_a_r=_v_a_l_u_e is treated as an assignment, not a filename.

     An input line is made up of fields separated by white space,
     or by regular expression FFSS.  The fields are denoted $$11, $$22,
     ...; $$00 refers to the entire line.

     A pattern-action statement has the form

          _p_a_t_t_e_r_n {{ _a_c_t_i_o_n }}

     A missing {{ _a_c_t_i_o_n }} 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:

          iiff(( _e_x_p_r_e_s_s_i_o_n )) _s_t_a_t_e_m_e_n_t [ eellssee _s_t_a_t_e_m_e_n_t ] wwhhiillee((
          _e_x_p_r_e_s_s_i_o_n )) _s_t_a_t_e_m_e_n_t ffoorr(( _e_x_p_r_e_s_s_i_o_n ;; _e_x_p_r_e_s_s_i_o_n ;;
          _e_x_p_r_e_s_s_i_o_n )) _s_t_a_t_e_m_e_n_t ffoorr(( _v_a_r iinn _a_r_r_a_y )) _s_t_a_t_e_m_e_n_t ddoo
          _s_t_a_t_e_m_e_n_t wwhhiillee(( _e_x_p_r_e_s_s_i_o_n )) bbrreeaakk ccoonnttiinnuuee {{ [ _s_t_a_t_e_-
          _m_e_n_t ... ] }} _e_x_p_r_e_s_s_i_o_n                ## commonly _v_a_r =
          _e_x_p_r_e_s_s_i_o_n pprriinntt [ _e_x_p_r_e_s_s_i_o_n-_l_i_s_t ] [ >> _e_x_p_r_e_s_s_i_o_n ]
          pprriinnttff _f_o_r_m_a_t [ ,, _e_x_p_r_e_s_s_i_o_n-_l_i_s_t ] [ >> _e_x_p_r_e_s_s_i_o_n ]
          rreettuurrnn [ _e_x_p_r_e_s_s_i_o_n ] nneexxtt                      ## skip
          remaining patterns on this input line ddeelleettee _a_r_r_a_y[[
          _e_x_p_r_e_s_s_i_o_n ]]## delete an array element eexxiitt [ _e_x_p_r_e_s_s_i_o_n
          ]       ## exit immediately; status is _e_x_p_r_e_s_s_i_o_n

     Statements are terminated by semicolons, newlines or right
     braces.  An empty _e_x_p_r_e_s_s_i_o_n-_l_i_s_t stands for $$00.  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 a
     blank).  The operators ++++ ---- ++== --== **== //== %%== ^^== ****== >> >>== << <<==
     ==== !!== ??:: are also available in expressions.  Variables may



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     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
     [[ii,,jj,,kk]] are permitted; the constituents are concatenated,
     separated by the value of SSUUBBSSEEPP.

     The pprriinntt statement prints its arguments on the standard
     output (or on a file if >>_f_i_l_e or >>>>_f_i_l_e is present or on a
     pipe if ||_c_m_d is present), separated by the current output
     field separator, and terminated by the output record separa-
     tor.  _f_i_l_e and _c_m_d may be literal names or parenthesized
     expressions; identical string values in different statements
     denote the same open file.  The pprriinnttff statement formats its
     expression list according to the format (see _p_r_i_n_t_f(3)).
     The built-in function cclloossee((_e_x_p_r)) closes the file or pipe
     _e_x_p_r.

     The customary functions eexxpp, lloogg, ssqqrrtt, ssiinn, ccooss, aattaann22 are
     built in.  Other built-in functions:

     lleennggtthh
          the length of its argument taken as a string, or of $$00
          if no argument.

     rraanndd random number on (0,1)

     ssrraanndd
          sets seed for rraanndd

     iinntt  truncates to an integer value

     ssuubbssttrr((_s,, _m,, _n))
          the _n-character substring of _s that begins at position
          _m counted from 1.

     iinnddeexx((_s,, _t))
          the position in _s where the string _t occurs, or 0 if it
          does not.

     mmaattcchh((_s,, _r))
          the position in _s where the regular expression _r
          occurs, or 0 if it does not.  The variables RRSSTTAARRTT and
          RRLLEENNGGTTHH are set to the position and length of the
          matched string.

     sspplliitt((_s,, _a,, _f_s))
          splits the string _s into array elements _a[[11]], _a[[22]],
          ..., _a[[_n]], and returns _n.  The separation is done with
          the regular expression _f_s or with the field separator
          FFSS if _f_s is not given.




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     ssuubb((_r,, _t,, _s))
          substitutes _t for the first occurrence of the regular
          expression _r in the string _s.  If _s is not given, $$00 is
          used.

     ggssuubb same as ssuubb except that all occurrences of the regular
          expression are replaced; ssuubb and ggssuubb return the number
          of replacements.

     sspprriinnttff((_f_m_t,, _e_x_p_r,, ... ))
          the string resulting from formatting _e_x_p_r ... according
          to the _p_r_i_n_t_f(3) format _f_m_t

     ssyysstteemm((_c_m_d))
          executes _c_m_d and returns its exit status

     The ``function'' ggeettlliinnee sets $$00 ttoo the next input record
     from the current input file; ggeettlliinnee <<_f_i_l_e sets $$00 to the
     next record from _f_i_l_e.  ggeettlliinnee _x sets variable _x instead.
     Finally, _c_m_d || ggeettlliinnee pipes the output of _c_m_d into ggeettlliinnee;
     each call of ggeettlliinnee returns the next line of output from
     _c_m_d.  In all cases, ggeettlliinnee 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 _e_g_r_e_p(1).  Isolated regular expres-
     sions in a pattern apply to the entire line.  Regular
     expressions may also occur in relational expressions, using
     the operators ~~ and !!~~.  //_r_e// 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:

          _e_x_p_r_e_s_s_i_o_n _m_a_t_c_h_o_p _r_e_g_u_l_a_r-_e_x_p_r_e_s_s_i_o_n
          _e_x_p_r_e_s_s_i_o_n _r_e_l_o_p _e_x_p_r_e_s_s_i_o_n

     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 BBEEGGIINN and EENNDD may be used to capture
     control before the first input line is read and after the
     last.  BBEEGGIINN and EENNDD do not combine with other patterns.



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     Variable names with special meanings:

     FFSS   regular expression used to separate fields; also sett-
          able by option --FF_f_s.

     NNFF   number of fields in the current record

     NNRR   ordinal number of the current record

     FFNNRR  ordinal number of the current record in the current
          file

     FFIILLEENNAAMMEE
          the name of the current input file

     RRSS   input record separator (default newline)

     OOFFSS  output field separator (default blank)

     OORRSS  output record separator (default newline)

     OOFFMMTT output format for numbers (default %%..66gg)

     SSUUBBSSEEPP
          separates multiple subscripts (default 034)

     AARRGGCC argument count, assignable

     AARRGGVV argument array, assignable; non-null members are taken
          as filenames

     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.

EEXXAAMMPPLLEESS
     length > 72

          Print lines longer than 72 characters.

     { print $2, $1 }

          Print first two fields in opposite order.

     BEGIN     { FS = ",[ \t]*|[ \t]+" }
          { print $2, $1 }




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          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 }

SSEEEE AALLSSOO
     lex(1), sed(1)
     A. V. Aho, B. W. Kernighan, P. J. Weinberger, _A_w_k - _a _P_a_t_-
     _t_e_r_n _S_c_a_n_n_i_n_g _a_n_d _P_r_o_c_e_s_s_i_n_g _L_a_n_g_u_a_g_e: _U_s_e_r'_s _M_a_n_u_a_l

BBUUGGSS
     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 concaten-
     ate "" to it.
     The scope rules for variables in functions are a botch.
     The (undocumented) options --SS and --RR are flaky.


























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