Aminet 3

home *** CD-ROM | disk | FTP | other *** search

/ Aminet 3 / Aminet 3 - July 1994.iso / Aminet / util / cli / ATT_awk_1_0.lha / AT&T-awk / awk.man < prev next >

Wrap

Text File | 1994-06-02 | 13.0 KB | 331 lines

AWK(1) AWK(1) NNAAMMEE awk - pattern-directed scanning and processing language SSYYNNOOPPSSIISS aawwkk [ --FF _f_s ] [ --vv _v_a_r_=_v_a_l_u_e ] [ _'_p_r_o_g_' | --ff _p_r_o_g_f_i_l_e ] [ _f_i_l_e _._._. ] 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 one or more files specified as --ff _p_r_o_g_f_i_l_e. With each pattern there can be an associated action that will be performed when a line of a _f_i_l_e 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 _f_i_l_e of the form _v_a_r_=_v_a_l_u_e is treated as an assignment, not a filename, and is executed at the time it would have been opened if it were a filename. The option --vv followed by _v_a_r_=_v_a_l_u_e is an assignment to be done before _p_r_o_g is executed; any number of --vv options may be present. The --FF _f_s option defines the input field separa tor to be the regular expression _f_s_. An input line is normally made up of fields separated by white space. (This default can be changed by using the FS built-in variable or the --FF _f_s option.) The fields are denoted $$11, $$22, ..., while $$00 refers to the entire line. A pattern-action statement has the form _p_a_t_t_e_r_n {{ _a_c_t_i_o_n }} A missing {{ _a_c_t_i_o_n }} means print the line; a missing pat tern always matches. Pattern-action statements are sepa rated by newlines or semicolons. An action is a sequence of statements. A statement can be one of the following: if( _e_x_p_r_e_s_s_i_o_n ) _s_t_a_t_e_m_e_n_t [ else _s_t_a_t_e_m_e_n_t ] while( _e_x_p_r_e_s_s_i_o_n ) _s_t_a_t_e_m_e_n_t for( _e_x_p_r_e_s_s_i_o_n ; _e_x_p_r_e_s_s_i_o_n ; _e_x_p_r_e_s_s_i_o_n ) _s_t_a_t_e_m_e_n_t for( _v_a_r in _a_r_r_a_y ) _s_t_a_t_e_m_e_n_t do _s_t_a_t_e_m_e_n_t while( _e_x_p_r_e_s_s_i_o_n ) break continue { [ _s_t_a_t_e_m_e_n_t _._._. ] } _e_x_p_r_e_s_s_i_o_n # commonly _v_a_r _= _e_x_p_r_e_s_s_i_o_n print [ _e_x_p_r_e_s_s_i_o_n_-_l_i_s_t ] [ > _e_x_p_r_e_s_s_i_o_n ] printf _f_o_r_m_a_t [ , _e_x_p_r_e_s_s_i_o_n_-_l_i_s_t ] [ > _e_x_p_r_e_s_s_i_o_n ] return [ _e_x_p_r_e_s_s_i_o_n ] next # skip remaining patterns on this input line delete _a_r_r_a_y[ _e_x_p_r_e_s_s_i_o_n ]# delete an array element 1 AWK(1) AWK(1) exit [ _e_x_p_r_e_s_s_i_o_n ] # exit immediately; status is _e_x_p_r_e_s_s_i_o_n Statements are terminated by semicolons, newlines or right braces. An empty _e_x_p_r_e_s_s_i_o_n_-_l_i_s_t stands for $$00. String constants are quoted "" "", with the usual C escapes recog nized within. Expressions take on string or numeric val ues as appropriate, and are built using the operators ++ -- ** // %% ^^ (exponentiation), and concatenation (indicated by a blank). The operators !! ++++ ---- ++== --== **== //== %%== ^^== >> >>== << <<== ==== !!== ??:: are also available in expressions. Variables may be scalars, array elements (denoted _x[[_i]]_) or fields. Variables are initialized to the null string. Array sub scripts may be any string, not necessarily numeric; this allows for a form of associative memory. Multiple sub scripts 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 sepa rator. _f_i_l_e and _c_m_d may be literal names or parenthesized expressions; identical string values in different state ments 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 mathematical functions eexxpp, lloogg, ssqqrrtt, ssiinn, ccooss, and aattaann22 are built in. Other built-in functions: lleennggtthh the length of its argument taken as a string, or of $$00 if no argument. rraanndd random number on (0,1) ssrraanndd sets seed for rraanndd and returns the previous seed. iinntt truncates to an integer value ssuubbssttrr((_s,, _m,, _n)) the _n-character substring of _s that begins at posi tion _m counted from 1. iinnddeexx((_s,, _t)) the position in _s where the string _t occurs, or 0 if it does not. mmaattcchh((_s,, _r)) the position in _s where the regular expression _r occurs, or 0 if it does not. The variables RRSSTTAARRTT and RRLLEENNGGTTHH are set to the position and length of the matched string. 2 AWK(1) AWK(1) sspplliitt((_s,, _a,, _f_s)) splits the string _s into array elements _a[[11]]_, _a[[22]]_, ..., _a[[_n]]_, and returns _n. The separation is done with the regular expression _f_s or with the field separator FFSS if _f_s is not given. ssuubb((_r,, _t,, _s)) substitutes _t for the first occurrence of the regu lar expression _r in the string _s. If _s is not given, $$00 is used. ggssuubb same as ssuubb except that all occurrences of the reg ular 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 ggeett lliinnee; each call of ggeettlliinnee returns the next line of output from _c_m_d. In all cases, ggeettlliinnee returns 1 for a success ful input, 0 for end of file, and -1 for an error. Patterns are arbitrary Boolean combinations (with !! |||| &&&&) of regular expressions and relational expressions. Regu lar expressions are as in _e_g_r_e_p; see _g_r_e_p(1). Isolated regular expressions in a pattern apply to the entire line. Regular expressions may also occur in relational expres sions, using the operators ~~ and !!~~. //_r_e// is a constant regular expression; 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 occur rence 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 _e_x_p_r_e_s_s_i_o_n iinn _a_r_r_a_y_-_n_a_m_e ((_e_x_p_r,,_e_x_p_r_,_._._.)) iinn _a_r_r_a_y_-_n_a_m_e where a relop is any of the six relational operators in C, and a matchop is either ~~ (matches) or !!~~ (does not 3 AWK(1) AWK(1) 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. Variable names with special meanings: FFSS regular expression used to separate fields; also settable 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 EENNVVIIRROONN 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 pro viding excess parameters in the function definition. EEXXAAMMPPLLEESS 4 AWK(1) AWK(1) 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 } 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 _l_e_x(1), _s_e_d(1) A. V. Aho, B. W. Kernighan, P. J. Weinberger, _T_h_e _A_W_K _P_r_o_ _g_r_a_m_m_i_n_g _L_a_n_g_u_a_g_e_, Addison-Wesley, 1988. 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 con catenate """" to it. The scope rules for variables in functions are a botch; the syntax is worse. 5