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GAWK(1) Utility Commands GAWK(1) NNAAMMEE gawk - pattern scanning and processing language SSYYNNOOPPSSIISS ggaawwkk [ POSIX or GNU style options ] --ff _p_r_o_g_r_a_m_-_f_i_l_e [ ---- ] file ... ggaawwkk [ POSIX or GNU style options ] [ ---- ] _p_r_o_g_r_a_m_-_t_e_x_t file ... ppggaawwkk [ POSIX or GNU style options ] --ff _p_r_o_g_r_a_m_-_f_i_l_e [ ---- ] file ... ppggaawwkk [ POSIX or GNU style options ] [ ---- ] _p_r_o_g_r_a_m_-_t_e_x_t file ... DDEESSCCRRIIPPTTIIOONN _G_a_w_k is the GNU Project's implementation of the AWK pro gramming language. It conforms to the definition of the language in the POSIX 1003.2 Command Language And Utili ties Standard. This version in turn is based on the description in _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, by Aho, Kernighan, and Weinberger, with the additional features found in the System V Release 4 version of UNIX _a_w_k. _G_a_w_k also provides more recent Bell Laboratories _a_w_k exten sions, and a number of GNU-specific extensions. _P_g_a_w_k is the profiling version of _g_a_w_k. It is identical in every way to _g_a_w_k, except that programs run more slowly, and it automatically produces an execution profile in the file aawwkkpprrooff..oouutt when done. See the ----pprrooffiillee option, below. The command line consists of options to _g_a_w_k itself, the AWK program text (if not supplied via the --ff or ----ffiillee options), and values to be made available in the AARRGGCC and AARRGGVV pre-defined AWK variables. OOPPTTIIOONN FFOORRMMAATT _G_a_w_k options may be either traditional POSIX one letter options, or GNU style long options. POSIX options start with a single "-", while long options start with "--". Long options are provided for both GNU-specific features and for POSIX-mandated features. Following the POSIX standard, _g_a_w_k-specific options are supplied via arguments to the --WW option. Multiple --WW options may be supplied Each --WW option has a corresponding long option, as detailed below. Arguments to long options are either joined with the option by an == sign, with no intervening spaces, or they may be provided in the next command line argument. Long options may be abbreviated, as long as the abbreviation remains unique. OOPPTTIIOONNSS _G_a_w_k accepts the following options, listed alphabetically. --FF _f_s ----ffiieelldd--sseeppaarraattoorr _f_s Use _f_s for the input field separator (the value of the FFSS predefined variable). --vv _v_a_r==_v_a_l ----aassssiiggnn _v_a_r==_v_a_l Assign the value _v_a_l to the variable _v_a_r, before execution of the program begins. Such variable values are available to the BBEEGGIINN block of an AWK program. --ff _p_r_o_g_r_a_m_-_f_i_l_e ----ffiillee _p_r_o_g_r_a_m_-_f_i_l_e Read the AWK program source from the file _p_r_o_g_r_a_m_- _f_i_l_e, instead of from the first command line argu ment. Multiple --ff (or ----ffiillee) options may be used. --mmff _N_N_N --mmrr _N_N_N Set various memory limits to the value _N_N_N. The ff flag sets the maximum number of fields, and the rr flag sets the maximum record size. These two flags and the --mm option are from the Bell Laboratories research version of UNIX _a_w_k. They are ignored by _g_a_w_k, since _g_a_w_k has no pre-defined limits. --WW ccoommppaatt --WW ttrraaddiittiioonnaall ----ccoommppaatt ----ttrraaddiittiioonnaall Run in _c_o_m_p_a_t_i_b_i_l_i_t_y mode. In compatibility mode, _g_a_w_k behaves identically to UNIX _a_w_k; none of the GNU-specific extensions are recognized. The use of ----ttrraaddiittiioonnaall is preferred over the other forms of this option. See GGNNUU EEXXTTEENNSSIIOONNSS, below, for more information. --WW ccooppyylleefftt --WW ccooppyyrriigghhtt ----ccooppyylleefftt ----ccooppyyrriigghhtt Print the short version of the GNU copyright infor mation message on the standard output and exit suc cessfully. --WW dduummpp--vvaarriiaabblleess[==_f_i_l_e] ----dduummpp--vvaarriiaabblleess[==_f_i_l_e] Print a sorted list of global variables, their types and final values to _f_i_l_e. If no _f_i_l_e is pro vided, _g_a_w_k uses a file named _a_w_k_v_a_r_s_._o_u_t in the current directory. Having a list of all the global variables is a good way to look for typographical errors in your pro grams. You would also use this option if you have a large program with a lot of functions, and you want to be sure that your functions don't inadver tently use global variables that you meant to be local. (This is a particularly easy mistake to make with simple variable names like ii, jj, and so on.) --WW hheellpp --WW uussaaggee ----hheellpp ----uussaaggee Print a relatively short summary of the available options on the standard output. (Per the _G_N_U _C_o_d_ _i_n_g _S_t_a_n_d_a_r_d_s, these options cause an immediate, successful exit.) --WW lliinntt[==ffaattaall] ----lliinntt[==ffaattaall] Provide warnings about constructs that are dubious or non-portable to other AWK implementations. With an optional argument of ffaattaall, lint warnings become fatal errors. This may be drastic, but its use will certainly encourage the development of cleaner AWK programs. --WW lliinntt--oolldd ----lliinntt--oolldd Provide warnings about constructs that are not portable to the original version of Unix _a_w_k. --WW ggeenn--ppoo ----ggeenn--ppoo Scan and parse the AWK program, and generate a GNU ..ppoo format file on standard output with entries for all localizable strings in the program. The pro gram itself is not executed. See the GNU _g_e_t_t_e_x_t distribution for more information on ..ppoo files. --WW nnoonn--ddeecciimmaall--ddaattaa ----nnoonn--ddeecciimmaall--ddaattaa Recognize octal and hexadecimal values in input data. _U_s_e _t_h_i_s _o_p_t_i_o_n _w_i_t_h _g_r_e_a_t _c_a_u_t_i_o_n_! --WW ppoossiixx ----ppoossiixx This turns on _c_o_m_p_a_t_i_b_i_l_i_t_y mode, with the follow ing additional restrictions: \\xx escape sequences are not recognized. Only space and tab act as field separators when FFSS is set to a single space, newline does not. You cannot continue lines after ?? and ::. The synonym ffuunncc for the keyword ffuunnccttiioonn is not recognized. The operators **** and ****== cannot be used in place of ^^ and ^^==. The fffflluusshh(()) function is not available. --WW pprrooffiillee[==_p_r_o_f___f_i_l_e] ----pprrooffiillee[==_p_r_o_f___f_i_l_e] Send profiling data to _p_r_o_f___f_i_l_e. The default is aawwkkpprrooff..oouutt. When run with _g_a_w_k, the profile is just a "pretty printed" version of the program. When run with _p_g_a_w_k, the profile contains execution counts of each statement in the program in the left margin and function call counts for each user- defined function. --WW rree--iinntteerrvvaall ----rree--iinntteerrvvaall Enable the use of _i_n_t_e_r_v_a_l _e_x_p_r_e_s_s_i_o_n_s in regular expression matching (see RReegguullaarr EExxpprreessssiioonnss, below). Interval expressions were not tradition ally available in the AWK language. The POSIX standard added them, to make _a_w_k and _e_g_r_e_p consis tent with each other. However, their use is likely to break old AWK programs, so _g_a_w_k only provides them if they are requested with this option, or when ----ppoossiixx is specified. --WW ssoouurrccee _p_r_o_g_r_a_m_-_t_e_x_t ----ssoouurrccee _p_r_o_g_r_a_m_-_t_e_x_t Use _p_r_o_g_r_a_m_-_t_e_x_t as AWK program source code. This option allows the easy intermixing of library func tions (used via the --ff and ----ffiillee options) with source code entered on the command line. It is intended primarily for medium to large AWK programs used in shell scripts. --WW vveerrssiioonn ----vveerrssiioonn Print version information for this particular copy of _g_a_w_k on the standard output. This is useful mainly for knowing if the current copy of _g_a_w_k on your system is up to date with respect to whatever the Free Software Foundation is distributing. This is also useful when reporting bugs. (Per the _G_N_U _C_o_d_i_n_g _S_t_a_n_d_a_r_d_s, these options cause an immediate, successful exit.) ---- Signal the end of options. This is useful to allow further arguments to the AWK program itself to start with a "-". This is mainly for consistency with the argument parsing convention used by most other POSIX programs. In compatibility mode, any other options are flagged as invalid, but are otherwise ignored. In normal operation, as long as program text has been supplied, unknown options are passed on to the AWK program in the AARRGGVV array for processing. This is particularly useful for running AWK programs via the "#!" executable interpreter mechanism. AAWWKK PPRROOGGRRAAMM EEXXEECCUUTTIIOONN An AWK program consists of a sequence of pattern-action statements and optional function definitions. _p_a_t_t_e_r_n {{ _a_c_t_i_o_n _s_t_a_t_e_m_e_n_t_s }} ffuunnccttiioonn _n_a_m_e((_p_a_r_a_m_e_t_e_r _l_i_s_t)) {{ _s_t_a_t_e_m_e_n_t_s }} _G_a_w_k first reads the program source from the _p_r_o_g_r_a_m_- _f_i_l_e(s) if specified, from arguments to ----ssoouurrccee, or from the first non-option argument on the command line. The --ff and ----ssoouurrccee options may be used multiple times on the command line. _G_a_w_k reads the program text as if all the _p_r_o_g_r_a_m_-_f_i_l_es and command line source texts had been con catenated together. This is useful for building libraries of AWK functions, without having to include them in each new AWK program that uses them. It also provides the ability to mix library functions with command line pro grams. The environment variable AAWWKKPPAATTHH specifies a search path to use when finding source files named with the --ff option. If this variable does not exist, the default path is ""..:://uussrr//llooccaall//sshhaarree//aawwkk"". (The actual directory may vary, depending upon how _g_a_w_k was built and installed.) If a file name given to the --ff option contains a "/" character, no path search is performed. _G_a_w_k executes AWK programs in the following order. First, all variable assignments specified via the --vv option are performed. Next, _g_a_w_k compiles the program into an inter nal form. Then, _g_a_w_k executes the code in the BBEEGGIINN block(s) (if any), and then proceeds to read each file named in the AARRGGVV array. If there are no files named on the command line, _g_a_w_k reads the standard input. If a filename on the command line has the form _v_a_r==_v_a_l it is treated as a variable assignment. The variable _v_a_r will be assigned the value _v_a_l. (This happens after any BBEEGGIINN block(s) have been run.) Command line variable assignment is most useful for dynamically assigning values to the variables AWK uses to control how input is broken into fields and records. It is also useful for control ling state if multiple passes are needed over a single data file. If the value of a particular element of AARRGGVV is empty (""""), _g_a_w_k skips over it. For each record in the input, _g_a_w_k tests to see if it matches any _p_a_t_t_e_r_n in the AWK program. For each pattern that the record matches, the associated _a_c_t_i_o_n is exe cuted. The patterns are tested in the order they occur in the program. Finally, after all the input is exhausted, _g_a_w_k executes the code in the EENNDD block(s) (if any). VVAARRIIAABBLLEESS,, RREECCOORRDDSS AANNDD FFIIEELLDDSS AWK variables are dynamic; they come into existence when they are first used. Their values are either floating- point numbers or strings, or both, depending upon how they are used. AWK also has one dimensional arrays; arrays with multiple dimensions may be simulated. Several pre- defined variables are set as a program runs; these will be described as needed and summarized below. RReeccoorrddss Normally, records are separated by newline characters. You can control how records are separated by assigning values to the built-in variable RRSS. If RRSS is any single character, that character separates records. Otherwise, RRSS is a regular expression. Text in the input that matches this regular expression separates the record. However, in compatibility mode, only the first character of its string value is used for separating records. If RRSS is set to the null string, then records are separated by blank lines. When RRSS is set to the null string, the new line character always acts as a field separator, in addi tion to whatever value FFSS may have. FFiieellddss As each input record is read, _g_a_w_k splits the record into _f_i_e_l_d_s, using the value of the FFSS variable as the field separator. If FFSS is a single character, fields are sepa rated by that character. If FFSS is the null string, then each individual character becomes a separate field. Oth erwise, FFSS is expected to be a full regular expression. In the special case that FFSS is a single space, fields are separated by runs of spaces and/or tabs and/or newlines. (But see the discussion of ----ppoossiixx, below). NNOOTTEE:: The value of IIGGNNOORREECCAASSEE (see below) also affects how fields are split when FFSS is a regular expression, and how records are separated when RRSS is a regular expression. If the FFIIEELLDDWWIIDDTTHHSS variable is set to a space separated list of numbers, each field is expected to have fixed width, and _g_a_w_k splits up the record using the specified widths. The value of FFSS is ignored. Assigning a new value to FFSS overrides the use of FFIIEELLDDWWIIDDTTHHSS, and restores the default behavior. Each field in the input record may be referenced by its position, $$11, $$22, and so on. $$00 is the whole record. Fields need not be referenced by constants: nn == 55 pprriinntt $$nn prints the fifth field in the input record. The variable NNFF is set to the total number of fields in the input record. References to non-existent fields (i.e. fields after $$NNFF) produce the null-string. However, assigning to a non- existent field (e.g., $$((NNFF++22)) == 55) increases the value of NNFF, creates any intervening fields with the null string as their value, and causes the value of $$00 to be recomputed, with the fields being separated by the value of OOFFSS. Ref erences to negative numbered fields cause a fatal error. Decrementing NNFF causes the values of fields past the new value to be lost, and the value of $$00 to be recomputed, with the fields being separated by the value of OOFFSS. Assigning a value to an existing field causes the whole record to be rebuilt when $$00 is referenced. Similarly, assigning a value to $$00 causes the record to be resplit, creating new values for the fields. BBuuiilltt--iinn VVaarriiaabblleess _G_a_w_k's built-in variables are: AARRGGCC The number of command line arguments (does not include options to _g_a_w_k, or the program source). AARRGGIINNDD The index in AARRGGVV of the current file being processed. AARRGGVV Array of command line arguments. The array is indexed from 0 to AARRGGCC - 1. Dynamically changing the contents of AARRGGVV can control the files used for data. BBIINNMMOODDEE On non-POSIX systems, specifies use of "binary" mode for all file I/O. Numeric val ues of 1, 2, or 3, specify that input files, output files, or all files, respectively, should use binary I/O. String values of ""rr"", or ""ww"" specify that input files, or output files, respectively, should use binary I/O. String values of ""rrww"" or ""wwrr"" specify that all files should use binary I/O. Any other string value is treated as ""rrww"", but generates a warning message. CCOONNVVFFMMTT The conversion format for numbers, ""%%..66gg"", by default. EENNVVIIRROONN An array containing the values of the current environment. The array is indexed by the environment variables, each element being the value of that variable (e.g., EENNVVIIRROONN[[""HHOOMMEE""]] might be //hhoommee//aarrnnoolldd). Changing this array does not affect the environment seen by pro grams which _g_a_w_k spawns via redirection or the ssyysstteemm(()) function. EERRRRNNOO If a system error occurs either doing a redi rection for ggeettlliinnee, during a read for ggeett lliinnee, or during a cclloossee(()), then EERRRRNNOO will contain a string describing the error. The value is subject to translation in non-English locales. FFIIEELLDDWWIIDDTTHHSS A white-space separated list of fieldwidths. When set, _g_a_w_k parses the input into fields of fixed width, instead of using the value of the FFSS variable as the field separator. FFIILLEENNAAMMEE The name of the current input file. If no files are specified on the command line, the value of FFIILLEENNAAMMEE is "-". However, FFIILLEENNAAMMEE is undefined inside the BBEEGGIINN block (unless set by ggeettlliinnee). FFNNRR The input record number in the current input file. FFSS The input field separator, a space by default. See FFiieellddss, above. IIGGNNOORREECCAASSEE Controls the case-sensitivity of all regular expression and string operations. If IIGGNNOORREE CCAASSEE has a non-zero value, then string compar isons and pattern matching in rules, field splitting with FFSS, record separating with RRSS, regular expression matching with ~~ and !!~~, and the ggeennssuubb(()), ggssuubb(()), iinnddeexx(()), mmaattcchh(()), sspplliitt(()), and ssuubb(()) built-in functions all ignore case when doing regular expression operations. NNOOTTEE:: Array subscripting is _n_o_t affected, nor is the aassoorrtt(()) function. Thus, if IIGGNNOORREECCAASSEE is not equal to zero, //aaBB// matches all of the strings ""aabb"", ""aaBB"", ""AAbb"", and ""AABB"". As with all AWK variables, the ini tial value of IIGGNNOORREECCAASSEE is zero, so all regu lar expression and string operations are nor mally case-sensitive. Under Unix, the full ISO 8859-1 Latin-1 character set is used when ignoring case. LLIINNTT Provides dynamic control of the ----lliinntt option from within an AWK program. When true, _g_a_w_k prints lint warnings. When false, it does not. When assigned the string value ""ffaattaall"", lint warnings become fatal errors, exactly like ----lliinntt==ffaattaall. Any other true value just prints warnings. NNFF The number of fields in the current input record. NNRR The total number of input records seen so far. OOFFMMTT The output format for numbers, ""%%..66gg"", by default. OOFFSS The output field separator, a space by default. OORRSS The output record separator, by default a new line. PPRROOCCIINNFFOO The elements of this array provide access to information about the running AWK program. On some systems, there may be elements in the array, ""ggrroouupp11"" through ""ggrroouupp_n"" for some _n, which is the number of supplementary groups that the process has. Use the iinn operator to test for these elements. The following ele ments are guaranteed to be available: PPRROOCCIINNFFOO[[""eeggiidd""]] the value of the _g_e_t_e_g_i_d(2) system call. PPRROOCCIINNFFOO[[""eeuuiidd""]] the value of the _g_e_t_e_u_i_d(2) system call. PPRROOCCIINNFFOO[[""FFSS""]] ""FFSS"" if field splitting with FFSS is in effect, or ""FFIIEELLDDWWIIDDTTHHSS"" if field splitting with FFIIEELLDDWWIIDDTTHHSS is in effect. PPRROOCCIINNFFOO[[""ggiidd""]] the value of the _g_e_t_g_i_d(2) system call. PPRROOCCIINNFFOO[[""ppggrrppiidd""]] the process group ID of the current process. PPRROOCCIINNFFOO[[""ppiidd""]] the process ID of the cur rent process. PPRROOCCIINNFFOO[[""ppppiidd""]] the parent process ID of the current process. PPRROOCCIINNFFOO[[""uuiidd""]] the value of the _g_e_t_u_i_d(2) system call. RRSS The input record separator, by default a new line. RRTT The record terminator. _G_a_w_k sets RRTT to the input text that matched the character or regu lar expression specified by RRSS. RRSSTTAARRTT The index of the first character matched by mmaattcchh(()); 0 if no match. (This implies that character indices start at one.) RRLLEENNGGTTHH The length of the string matched by mmaattcchh(()); -1 if no match. SSUUBBSSEEPP The character used to separate multiple sub scripts in array elements, by default ""\\003344"". TTEEXXTTDDOOMMAAIINN The text domain of the AWK program; used to find the localized translations for the pro gram's strings. AArrrraayyss Arrays are subscripted with an expression between square brackets ([[ and ]]). If the expression is an expression list (_e_x_p_r, _e_x_p_r ...) then the array subscript is a string consisting of the concatenation of the (string) value of each expression, separated by the value of the SSUUBBSSEEPP variable. This facility is used to simulate multi ply dimensioned arrays. For example: ii == ""AA"";; jj == ""BB"";; kk == ""CC"" xx[[ii,, jj,, kk]] == ""hheelllloo,, wwoorrlldd\\nn"" assigns the string ""hheelllloo,, wwoorrlldd\\nn"" to the element of the array xx which is indexed by the string ""AA\\003344BB\\003344CC"". All arrays in AWK are associative, i.e. indexed by string val ues. The special operator iinn may be used in an iiff or wwhhiillee statement to see if an array has an index consisting of a particular value. iiff ((vvaall iinn aarrrraayy)) pprriinntt aarrrraayy[[vvaall]] If the array has multiple subscripts, use ((ii,, jj)) iinn aarrrraayy. The iinn construct may also be used in a ffoorr loop to iterate over all the elements of an array. An element may be deleted from an array using the ddeelleettee statement. The ddeelleettee statement may also be used to delete the entire contents of an array, just by specifying the array name without a subscript. VVaarriiaabbllee TTyyppiinngg AAnndd CCoonnvveerrssiioonn Variables and fields may be (floating point) numbers, or strings, or both. How the value of a variable is inter preted depends upon its context. If used in a numeric expression, it will be treated as a number, if used as a string it will be treated as a string. To force a variable to be treated as a number, add 0 to it; to force it to be treated as a string, concatenate it with the null string. When a string must be converted to a number, the conver sion is accomplished using _s_t_r_t_o_d(3). A number is con verted to a string by using the value of CCOONNVVFFMMTT as a for mat string for _s_p_r_i_n_t_f(3), with the numeric value of the variable as the argument. However, even though all num bers in AWK are floating-point, integral values are _a_l_w_a_y_s converted as integers. Thus, given CCOONNVVFFMMTT == ""%%22..22ff"" aa == 1122 bb == aa """" the variable bb has a string value of ""1122"" and not ""1122..0000"". _G_a_w_k performs comparisons as follows: If two variables are numeric, they are compared numerically. If one value is numeric and the other has a string value that is a "numeric string," then comparisons are also done numeri cally. Otherwise, the numeric value is converted to a string and a string comparison is performed. Two strings are compared, of course, as strings. Note that the POSIX standard applies the concept of "numeric string" every where, even to string constants. However, this is clearly incorrect, and _g_a_w_k does not do this. (Fortunately, this is fixed in the next version of the standard.) Note that string constants, such as ""5577"", are _n_o_t numeric strings, they are string constants. The idea of "numeric string" only applies to fields, ggeettlliinnee input, FFIILLEENNAAMMEE, AARRGGVV elements, EENNVVIIRROONN elements and the elements of an array created by sspplliitt(()) that are numeric strings. The basic idea is that _u_s_e_r _i_n_p_u_t, and only user input, that looks numeric, should be treated that way. Uninitialized variables have the numeric value 0 and the string value "" (the null, or empty, string). OOccttaall aanndd HHeexxaaddeecciimmaall CCoonnssttaannttss Starting with version 3.1 of _g_a_w_k _, you may use C-style octal and hexadecimal constants in your AWK program source code. For example, the octal value 001111 is equal to deci mal 99, and the hexadecimal value 00xx1111 is equal to decimal 17. SSttrriinngg CCoonnssttaannttss String constants in AWK are sequences of characters enclosed between double quotes (""). Within strings, cer tain _e_s_c_a_p_e _s_e_q_u_e_n_c_e_s are recognized, as in C. These are: \\\\ A literal backslash. \\aa The "alert" character; usually the ASCII BEL charac ter. \\bb backspace. \\ff form-feed. \\nn newline. \\rr carriage return. \\tt horizontal tab. \\vv vertical tab. \\xx_h_e_x _d_i_g_i_t_s The character represented by the string of hexadeci mal digits following the \\xx. As in ANSI C, all fol lowing hexadecimal digits are considered part of the escape sequence. (This feature should tell us some thing about language design by committee.) E.g., ""\\xx11BB"" is the ASCII ESC (escape) character. \\_d_d_d The character represented by the 1-, 2-, or 3-digit sequence of octal digits. E.g., ""\\003333"" is the ASCII ESC (escape) character. \\_c The literal character _c. The escape sequences may also be used inside constant reg ular expressions (e.g., //[[ \\tt\\ff\\nn\\rr\\vv]]// matches whitespace characters). In compatibility mode, the characters represented by octal and hexadecimal escape sequences are treated literally when used in regular expression constants. Thus, //aa\\5522bb// is equivalent to //aa\\**bb//. PPAATTTTEERRNNSS AANNDD AACCTTIIOONNSS AWK is a line-oriented language. The pattern comes first, and then the action. Action statements are enclosed in {{ and }}. Either the pattern may be missing, or the action may be missing, but, of course, not both. If the pattern is missing, the action is executed for every single record of input. A missing action is equivalent to {{ pprriinntt }} which prints the entire record. Comments begin with the "#" character, and continue until the end of the line. Blank lines may be used to separate statements. Normally, a statement ends with a newline, however, this is not the case for lines ending in a ",", {{, ??, ::, &&&&, or ||||. Lines ending in ddoo or eellssee also have their statements automatically continued on the following line. In other cases, a line can be continued by ending it with a "\", in which case the newline will be ignored. Multiple statements may be put on one line by separating them with a ";". This applies to both the statements within the action part of a pattern-action pair (the usual case), and to the pattern-action statements themselves. PPaatttteerrnnss AWK patterns may be one of the following: BBEEGGIINN EENNDD //_r_e_g_u_l_a_r _e_x_p_r_e_s_s_i_o_n// _r_e_l_a_t_i_o_n_a_l _e_x_p_r_e_s_s_i_o_n _p_a_t_t_e_r_n &&&& _p_a_t_t_e_r_n _p_a_t_t_e_r_n |||| _p_a_t_t_e_r_n _p_a_t_t_e_r_n ?? _p_a_t_t_e_r_n :: _p_a_t_t_e_r_n ((_p_a_t_t_e_r_n)) !! _p_a_t_t_e_r_n _p_a_t_t_e_r_n_1,, _p_a_t_t_e_r_n_2 BBEEGGIINN and EENNDD are two special kinds of patterns which are not tested against the input. The action parts of all BBEEGGIINN patterns are merged as if all the statements had been written in a single BBEEGGIINN block. They are executed before any of the input is read. Similarly, all the EENNDD blocks are merged, and executed when all the input is exhausted (or when an eexxiitt statement is executed). BBEEGGIINN and EENNDD patterns cannot be combined with other patterns in pattern expressions. BBEEGGIINN and EENNDD patterns cannot have missing action parts. For //_r_e_g_u_l_a_r _e_x_p_r_e_s_s_i_o_n// patterns, the associated state ment is executed for each input record that matches the regular expression. Regular expressions are the same as those in _e_g_r_e_p(1), and are summarized below. A _r_e_l_a_t_i_o_n_a_l _e_x_p_r_e_s_s_i_o_n may use any of the operators defined below in the section on actions. These generally test whether certain fields match certain regular expres sions. The &&&&, ||||, and !! operators are logical AND, logical OR, and logical NOT, respectively, as in C. They do short- circuit evaluation, also as in C, and are used for combin ing more primitive pattern expressions. As in most lan guages, parentheses may be used to change the order of evaluation. The ??:: operator is like the same operator in C. If the first pattern is true then the pattern used for testing is the second pattern, otherwise it is the third. Only one of the second and third patterns is evaluated. The _p_a_t_t_e_r_n_1,, _p_a_t_t_e_r_n_2 form of an expression is called a _r_a_n_g_e _p_a_t_t_e_r_n. It matches all input records starting with a record that matches _p_a_t_t_e_r_n_1, and continuing until a record that matches _p_a_t_t_e_r_n_2, inclusive. It does not com bine with any other sort of pattern expression. RReegguullaarr EExxpprreessssiioonnss Regular expressions are the extended kind found in _e_g_r_e_p. They are composed of characters as follows: _c matches the non-metacharacter _c. _\_c matches the literal character _c. .. matches any character _i_n_c_l_u_d_i_n_g newline. ^^ matches the beginning of a string. $$ matches the end of a string. [[_a_b_c_._._.]] character list, matches any of the characters _a_b_c_._._.. [[^^_a_b_c_._._.]] negated character list, matches any character except _a_b_c_._._.. _r_1||_r_2 alternation: matches either _r_1 or _r_2. _r_1_r_2 concatenation: matches _r_1, and then _r_2. _r++ matches one or more _r's. _r** matches zero or more _r's. _r?? matches zero or one _r's. ((_r)) grouping: matches _r. _r{{_n}} _r{{_n,,}} _r{{_n,,_m}} One or two numbers inside braces denote an _i_n_t_e_r_v_a_l _e_x_p_r_e_s_s_i_o_n. If there is one number in the braces, the preceding regular expression _r is repeated _n times. If there are two numbers separated by a comma, _r is repeated _n to _m times. If there is one number followed by a comma, then _r is repeated at least _n times. Interval expressions are only available if either ----ppoossiixx or ----rree--iinntteerrvvaall is specified on the command line. \\yy matches the empty string at either the begin ning or the end of a word. \\BB matches the empty string within a word. \\<< matches the empty string at the beginning of a word. \\>> matches the empty string at the end of a word. \\ww matches any word-constituent character (letter, digit, or underscore). \\WW matches any character that is not word-con stituent. \\`` matches the empty string at the beginning of a buffer (string). \\'' matches the empty string at the end of a buffer. The escape sequences that are valid in string constants (see below) are also valid in regular expressions. _C_h_a_r_a_c_t_e_r _c_l_a_s_s_e_s are a new feature introduced in the POSIX standard. A character class is a special notation for describing lists of characters that have a specific attribute, but where the actual characters themselves can vary from country to country and/or from character set to character set. For example, the notion of what is an alphabetic character differs in the USA and in France. A character class is only valid in a regular expression _i_n_s_i_d_e the brackets of a character list. Character classes consist of [[::, a keyword denoting the class, and ::]]. The character classes defined by the POSIX standard are: [[::aallnnuumm::]] Alphanumeric characters. [[::aallpphhaa::]] Alphabetic characters. [[::bbllaannkk::]] Space or tab characters. [[::ccnnttrrll::]] Control characters. [[::ddiiggiitt::]] Numeric characters. [[::ggrraapphh::]] Characters that are both printable and visible. (A space is printable, but not visible, while an aa is both.) [[::lloowweerr::]] Lower-case alphabetic characters. [[::pprriinntt::]] Printable characters (characters that are not control characters.) [[::ppuunncctt::]] Punctuation characters (characters that are not letter, digits, control characters, or space characters). [[::ssppaaccee::]] Space characters (such as space, tab, and form feed, to name a few). [[::uuppppeerr::]] Upper-case alphabetic characters. [[::xxddiiggiitt::]] Characters that are hexadecimal digits. For example, before the POSIX standard, to match alphanu meric characters, you would have had to write //[[AA--ZZaa--zz00--99]]//. If your character set had other alphabetic characters in it, this would not match them, and if your character set collated differently from ASCII, this might not even match the ASCII alphanumeric characters. With the POSIX character classes, you can write //[[[[::aallnnuumm::]]]]//, and this matches the alphabetic and numeric characters in your character set. Two additional special sequences can appear in character lists. These apply to non-ASCII character sets, which can have single symbols (called _c_o_l_l_a_t_i_n_g _e_l_e_m_e_n_t_s) that are represented with more than one character, as well as sev eral characters that are equivalent for _c_o_l_l_a_t_i_n_g, or sorting, purposes. (E.g., in French, a plain "e" and a grave-accented e` are equivalent.) Collating Symbols A collating symbol is a multi-character collating element enclosed in [[.. and ..]]. For example, if cchh is a collating element, then [[[[..cchh..]]]] is a regular expression that matches this collating element, while [[cchh]] is a regular expression that matches either cc or hh. Equivalence Classes An equivalence class is a locale-specific name for a list of characters that are equivalent. The name is enclosed in [[== and ==]]. For example, the name ee might be used to represent all of "e," "e," and "e`." In this case, [[[[==ee==]]]] is a regular expression that matches any of ee,,eeor ee``. These features are very valuable in non-English speaking locales. The library functions that _g_a_w_k uses for regular expression matching currently only recognize POSIX charac ter classes; they do not recognize collating symbols or equivalence classes. The \\yy, \\BB, \\<<, \\>>, \\ww, \\WW, \\``, and \\'' operators are spe cific to _g_a_w_k; they are extensions based on facilities in the GNU regular expression libraries. The various command line options control how _g_a_w_k inter prets characters in regular expressions. No options In the default case, _g_a_w_k provide all the facili ties of POSIX regular expressions and the GNU regu lar expression operators described above. However, interval expressions are not supported. ----ppoossiixx Only POSIX regular expressions are supported, the GNU operators are not special. (E.g., \\ww matches a literal ww). Interval expressions are allowed. ----ttrraaddiittiioonnaall Traditional Unix _a_w_k regular expressions are matched. The GNU operators are not special, inter val expressions are not available, and neither are the POSIX character classes ([[[[::aallnnuumm::]]]] and so on). Characters described by octal and hexadecimal escape sequences are treated literally, even if they represent regular expression metacharacters. ----rree--iinntteerrvvaall Allow interval expressions in regular expressions, even if ----ttrraaddiittiioonnaall has been provided. AAccttiioonnss Action statements are enclosed in braces, {{ and }}. Action statements consist of the usual assignment, conditional, and looping statements found in most languages. The oper ators, control statements, and input/output statements available are patterned after those in C. OOppeerraattoorrss The operators in AWK, in order of decreasing precedence, are ((...)) Grouping $$ Field reference. ++++ ---- Increment and decrement, both prefix and post fix. ^^ Exponentiation (**** may also be used, and ****== for the assignment operator). ++ -- !! Unary plus, unary minus, and logical negation. ** // %% Multiplication, division, and modulus. ++ -- Addition and subtraction. _s_p_a_c_e String concatenation. << >> <<== >>== !!== ==== The regular relational operators. ~~ !!~~ Regular expression match, negated match. NNOOTTEE:: Do not use a constant regular expression (//ffoooo//) on the left-hand side of a ~~ or !!~~. Only use one on the right-hand side. The expression //ffoooo// ~~ _e_x_p has the same meaning as (((($$00 ~~ //ffoooo//)) ~~ _e_x_p)). This is usually _n_o_t what was intended. iinn Array membership. &&&& Logical AND. |||| Logical OR. ??:: The C conditional expression. This has the form _e_x_p_r_1 ?? _e_x_p_r_2 :: _e_x_p_r_3. If _e_x_p_r_1 is true, the value of the expression is _e_x_p_r_2, other wise it is _e_x_p_r_3. Only one of _e_x_p_r_2 and _e_x_p_r_3 is evaluated. == ++== --== **== //== %%== ^^== Assignment. Both absolute assignment ((_v_a_r == _v_a_l_u_e)) and operator-assignment (the other forms) are supported. CCoonnttrrooll SSttaatteemmeennttss The control statements are as follows: iiff ((_c_o_n_d_i_t_i_o_n)) _s_t_a_t_e_m_e_n_t [ eellssee _s_t_a_t_e_m_e_n_t ] wwhhiillee ((_c_o_n_d_i_t_i_o_n)) _s_t_a_t_e_m_e_n_t ddoo _s_t_a_t_e_m_e_n_t wwhhiillee ((_c_o_n_d_i_t_i_o_n)) ffoorr ((_e_x_p_r_1;; _e_x_p_r_2;; _e_x_p_r_3)) _s_t_a_t_e_m_e_n_t ffoorr ((_v_a_r iinn _a_r_r_a_y)) _s_t_a_t_e_m_e_n_t bbrreeaakk ccoonnttiinnuuee ddeelleettee _a_r_r_a_y[[_i_n_d_e_x]] ddeelleettee _a_r_r_a_y eexxiitt [ _e_x_p_r_e_s_s_i_o_n ] {{ _s_t_a_t_e_m_e_n_t_s }} II//OO SSttaatteemmeennttss The input/output statements are as follows: cclloossee((_f_i_l_e [,, _h_o_w])) Close file, pipe or co-process. The optional _h_o_w should only be used when closing one end of a two-way pipe to a co-process. It must be a string value, either ""ttoo"" or ""ffrroomm"". ggeettlliinnee Set $$00 from next input record; set NNFF, NNRR, FFNNRR. ggeettlliinnee <<_f_i_l_e Set $$00 from next record of _f_i_l_e; set NNFF. ggeettlliinnee _v_a_r Set _v_a_r from next input record; set NNRR, FFNNRR. ggeettlliinnee _v_a_r <<_f_i_l_e Set _v_a_r from next record of _f_i_l_e. _c_o_m_m_a_n_d || ggeettlliinnee [_v_a_r] Run _c_o_m_m_a_n_d piping the output either into $$00 or _v_a_r, as above. _c_o_m_m_a_n_d ||&& ggeettlliinnee [_v_a_r] Run _c_o_m_m_a_n_d as a co-process piping the output either into $$00 or _v_a_r, as above. Co-processes are a _g_a_w_k extension. nneexxtt Stop processing the current input record. The next input record is read and processing starts over with the first pattern in the AWK pro gram. If the end of the input data is reached, the EENNDD block(s), if any, are executed. nneexxttffiillee Stop processing the current input file. The next input record read comes from the next input file. FFIILLEENNAAMMEE and AARRGGIINNDD are updated, FFNNRR is reset to 1, and processing starts over with the first pattern in the AWK program. If the end of the input data is reached, the EENNDD block(s), if any, are executed. pprriinntt Prints the current record. The out put record is terminated with the value of the OORRSS variable. pprriinntt _e_x_p_r_-_l_i_s_t Prints expressions. Each expression is separated by the value of the OOFFSS variable. The output record is ter minated with the value of the OORRSS variable. pprriinntt _e_x_p_r_-_l_i_s_t >>_f_i_l_e Prints expressions on _f_i_l_e. Each expression is separated by the value of the OOFFSS variable. The output record is terminated with the value of the OORRSS variable. pprriinnttff _f_m_t_, _e_x_p_r_-_l_i_s_t Format and print. pprriinnttff _f_m_t_, _e_x_p_r_-_l_i_s_t >>_f_i_l_e Format and print on _f_i_l_e. ssyysstteemm((_c_m_d_-_l_i_n_e)) Execute the command _c_m_d_-_l_i_n_e, and return the exit status. (This may not be available on non-POSIX sys tems.) fffflluusshh(([_f_i_l_e])) Flush any buffers associated with the open output file or pipe _f_i_l_e. If _f_i_l_e is missing, then standard output is flushed. If _f_i_l_e is the null string, then all open output files and pipes have their buffers flushed. Additional output redirections are allowed for pprriinntt and pprriinnttff. pprriinntt ...... >>>> _f_i_l_e appends output to the _f_i_l_e. pprriinntt ...... || _c_o_m_m_a_n_d writes on a pipe. pprriinntt ...... ||&& _c_o_m_m_a_n_d sends data to a co-process. The ggeettlliinnee command returns 0 on end of file and -1 on an error. Upon an error, EERRRRNNOO contains a string describing the problem. NNOOTTEE:: If using a pipe or co-process to ggeettlliinnee, or from pprriinntt or pprriinnttff within a loop, you _m_u_s_t use cclloossee(()) to create new instances of the command. AWK does not auto matically close pipes or co-processes when they return EOF. TThhee _p_r_i_n_t_f SSttaatteemmeenntt The AWK versions of the pprriinnttff statement and sspprriinnttff(()) function (see below) accept the following conversion specification formats: %%cc An ASCII character. If the argument used for %%cc is numeric, it is treated as a character and printed. Otherwise, the argument is assumed to be a string, and the only first character of that string is printed. %%dd, %%ii A decimal number (the integer part). %%ee ,, %%EE A floating point number of the form [[--]]dd..ddddddddddddee[[++--]]dddd. The %%EE format uses EE instead of ee. %%ff A floating point number of the form [[--]]dddddd..dddddddddddd. %%gg ,, %%GG Use %%ee or %%ff conversion, whichever is shorter, with nonsignificant zeros suppressed. The %%GG for mat uses %%EE instead of %%ee. %%oo An unsigned octal number (also an integer). %%uu An unsigned decimal number (again, an integer). %%ss A character string. %%xx ,, %%XX An unsigned hexadecimal number (an integer). The %%XX format uses AABBCCDDEEFF instead of aabbccddeeff. %%%% A single %% character; no argument is converted. Optional, additional parameters may lie between the %% and the control letter: _c_o_u_n_t$$ Use the _c_o_u_n_t'th argument at this point in the for matting. This is called a _p_o_s_i_t_i_o_n_a_l _s_p_e_c_i_f_i_e_r and is intended primarily for use in translated ver sions of format strings, not in the original text of an AWK program. It is a _g_a_w_k extension. -- The expression should be left-justified within its field. _s_p_a_c_e For numeric conversions, prefix positive values with a space, and negative values with a minus sign. ++ The plus sign, used before the width modifier (see below), says to always supply a sign for numeric conversions, even if the data to be formatted is positive. The ++ overrides the space modifier. ## Use an "alternate form" for certain control let ters. For %%oo, supply a leading zero. For %%xx, and %%XX, supply a leading 00xx or 00XX for a nonzero result. For %%ee, %%EE, and %%ff, the result always contains a decimal point. For %%gg, and %%GG, trailing zeros are not removed from the result. 00 A leading 00 (zero) acts as a flag, that indicates output should be padded with zeroes instead of spaces. This applies even to non-numeric output formats. This flag only has an effect when the field width is wider than the value to be printed. _w_i_d_t_h The field should be padded to this width. The field is normally padded with spaces. If the 00 flag has been used, it is padded with zeroes. .._p_r_e_c A number that specifies the precision to use when printing. For the %%ee, %%EE, and %%ff formats, this specifies the number of digits you want printed to the right of the decimal point. For the %%gg, and %%GG formats, it specifies the maximum number of signif icant digits. For the %%dd, %%oo, %%ii, %%uu, %%xx, and %%XX formats, it specifies the minimum number of digits to print. For %%ss, it specifies the maximum number of characters from the string that should be printed. The dynamic _w_i_d_t_h and _p_r_e_c capabilities of the ANSI C pprriinnttff(()) routines are supported. A ** in place of either the wwiiddtthh or pprreecc specifications causes their values to be taken from the argument list to pprriinnttff or sspprriinnttff(()). To use a positional specifier with a dynamic width or preci sion, supply the _c_o_u_n_t$$ after the ** in the format string. For example, ""%%33$$**22$$..**11$$ss"". SSppeecciiaall FFiillee NNaammeess When doing I/O redirection from either pprriinntt or pprriinnttff into a file, or via ggeettlliinnee from a file, _g_a_w_k recognizes certain special filenames internally. These filenames allow access to open file descriptors inherited from _g_a_w_k's parent process (usually the shell). These file names may also be used on the command line to name data files. The filenames are: //ddeevv//ssttddiinn The standard input. //ddeevv//ssttddoouutt The standard output. //ddeevv//ssttddeerrrr The standard error output. //ddeevv//ffdd//_n The file associated with the open file descriptor _n. These are particularly useful for error messages. For example: pprriinntt ""YYoouu bblleeww iitt!!"" >> ""//ddeevv//ssttddeerrrr"" whereas you would otherwise have to use pprriinntt ""YYoouu bblleeww iitt!!"" || ""ccaatt 11>>&&22"" The following special filenames may be used with the ||&& co-process operator for creating TCP/IP network connec tions. //iinneett//ttccpp//_l_p_o_r_t//_r_h_o_s_t//_r_p_o_r_t File for TCP/IP connection on local port _l_p_o_r_t to remote host _r_h_o_s_t on remote port _r_p_o_r_t. Use a port of 00 to have the system pick a port. //iinneett//uuddpp//_l_p_o_r_t//_r_h_o_s_t//_r_p_o_r_t Similar, but use UDP/IP instead of TCP/IP. //iinneett//rraaww//_l_p_o_r_t//_r_h_o_s_t//_r_p_o_r_t Reserved for future use. Other special filenames provide access to information about the running _g_a_w_k process. TThheessee ffiilleennaammeess aarree nnooww oobbssoolleettee.. Use the PPRROOCCIINNFFOO array to obtain the informa tion they provide. The filenames are: //ddeevv//ppiidd Reading this file returns the process ID of the current process, in decimal, terminated with a newline. //ddeevv//ppppiidd Reading this file returns the parent process ID of the current process, in decimal, termi nated with a newline. //ddeevv//ppggrrppiidd Reading this file returns the process group ID of the current process, in decimal, terminated with a newline. //ddeevv//uusseerr Reading this file returns a single record ter minated with a newline. The fields are sepa rated with spaces. $$11 is the value of the _g_e_t_u_i_d(2) system call, $$22 is the value of the _g_e_t_e_u_i_d(2) system call, $$33 is the value of the _g_e_t_g_i_d(2) system call, and $$44 is the value of the _g_e_t_e_g_i_d(2) system call. If there are any additional fields, they are the group IDs returned by _g_e_t_g_r_o_u_p_s(2). Multiple groups may not be supported on all systems. NNuummeerriicc FFuunnccttiioonnss AWK has the following built-in arithmetic functions: aattaann22((_y,, _x)) Returns the arctangent of _y_/_x in radians. ccooss((_e_x_p_r)) Returns the cosine of _e_x_p_r, which is in radians. eexxpp((_e_x_p_r)) The exponential function. iinntt((_e_x_p_r)) Truncates to integer. lloogg((_e_x_p_r)) The natural logarithm function. rraanndd(()) Returns a random number between 0 and 1. ssiinn((_e_x_p_r)) Returns the sine of _e_x_p_r, which is in radi ans. ssqqrrtt((_e_x_p_r)) The square root function. ssrraanndd(([_e_x_p_r])) Uses _e_x_p_r as a new seed for the random num ber generator. If no _e_x_p_r is provided, the time of day is used. The return value is the previous seed for the random number gen erator. SSttrriinngg FFuunnccttiioonnss _G_a_w_k has the following built-in string functions: aassoorrtt((_s [,, _d])) Returns the number of elements in the source array _s. The contents of _s are sorted using _g_a_w_k's nor mal rules for comparing values, and the indexes of the sorted values of _s are replaced with sequential integers starting with 1. If the optional destination array _d is specified, then _s is first duplicated into _d, and then _d is sorted, leaving the indexes of the source array _s unchanged. ggeennssuubb((_r,, _s,, _h [,, _t])) Search the target string _t for matches of the regular expression _r. If _h is a string beginning with gg or GG, then replace all matches of _r with _s. Otherwise, _h is a number indicating which match of _r to replace. If _t is not sup plied, $$00 is used instead. Within the replacement text _s, the sequence \\_n, where _n is a digit from 1 to 9, may be used to indi cate just the text that matched the _n'th parenthesized subexpres sion. The sequence \\00 represents the entire matched text, as does the character &&. Unlike ssuubb(()) and ggssuubb(()), the modified string is returned as the result of the function, and the original target string is _n_o_t changed. ggssuubb((_r,, _s [,, _t])) For each substring matching the regular expression _r in the string _t, substitute the string _s, and return the number of substitu tions. If _t is not supplied, use $$00. An && in the replacement text is replaced with the text that was actually matched. Use \\&& to get a literal &&. (This must be typed as ""\\\\&&""; see _G_A_W_K_: _E_f_f_e_c_t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g for a fuller discus sion of the rules for &&''ss and backslashes in the replacement text of ssuubb(()), ggssuubb(()), and ggeenn ssuubb(()).) iinnddeexx((_s,, _t)) Returns the index of the string _t in the string _s, or 0 if _t is not present. (This implies that char acter indices start at one.) lleennggtthh(([_s])) Returns the length of the string _s, or the length of $$00 if _s is not supplied. mmaattcchh((_s,, _r [,, _a])) Returns the position in _s where the regular expression _r occurs, or 0 if _r is not present, and sets the values of RRSSTTAARRTT and RRLLEENNGGTTHH. Note that the argument order is the same as for the ~~ operator: _s_t_r ~~ _r_e. If array _a is provided, _a is cleared and then elements 1 through _n are filled with the por tions of _s that match the corre sponding parenthesized subexpres sion in _r. The 0'th element of _a contains the portion of _s matched by the entire regular expression _r. sspplliitt((_s,, _a [,, _r])) Splits the string _s into the array _a on the regular expression _r, and returns the number of fields. If _r is omitted, FFSS is used instead. The array _a is cleared first. Splitting behaves identically to field splitting, described above. sspprriinnttff((_f_m_t,, _e_x_p_r_-_l_i_s_t)) Prints _e_x_p_r_-_l_i_s_t according to _f_m_t, and returns the resulting string. ssttrrttoonnuumm((_s_t_r)) Examines _s_t_r, and returns its numeric value. If _s_t_r begins with a leading 00, ssttrrttoonnuumm(()) assumes that _s_t_r is an octal number. If _s_t_r begins with a leading 00xx or 00XX, ssttrrttoonnuumm(()) assumes that _s_t_r is a hexadecimal number. ssuubb((_r,, _s [,, _t])) Just like ggssuubb(()), but only the first matching substring is replaced. ssuubbssttrr((_s,, _i [,, _n])) Returns the at most _n-character substring of _s starting at _i. If _n is omitted, the rest of _s is used. ttoolloowweerr((_s_t_r)) Returns a copy of the string _s_t_r, with all the upper-case characters in _s_t_r translated to their corre sponding lower-case counterparts. Non-alphabetic characters are left unchanged. ttoouuppppeerr((_s_t_r)) Returns a copy of the string _s_t_r, with all the lower-case characters in _s_t_r translated to their corre sponding upper-case counterparts. Non-alphabetic characters are left unchanged. TTiimmee FFuunnccttiioonnss Since one of the primary uses of AWK programs is process ing log files that contain time stamp information, _g_a_w_k provides the following functions for obtaining time stamps and formatting them. mmkkttiimmee((_d_a_t_e_s_p_e_c)) Rurns _d_a_t_e_s_p_e_c into a time stamp of the same form as returned by ssyyssttiimmee(()). The _d_a_t_e_s_p_e_c is a string of the form _Y_Y_Y_Y _M_M _D_D _H_H _M_M _S_S_[ _D_S_T_]. The contents of the string are six or seven num bers representing respectively the full year including century, the month from 1 to 12, the day of the month from 1 to 31, the hour of the day from 0 to 23, the minute from 0 to 59, and the second from 0 to 60, and an optional day light saving flag. The values of these numbers need not be within the ranges specified; for example, an hour of -1 means 1 hour before midnight. The origin-zero Gregorian calendar is assumed, with year 0 preceding year 1 and year -1 preceding year 0. The time is assumed to be in the local timezone. If the daylight saving flag is positive, the time is assumed to be day light saving time; if zero, the time is assumed to be standard time; and if negative (the default), mmkkttiimmee(()) attempts to determine whether daylight saving time is in effect for the speci fied time. If _d_a_t_e_s_p_e_c does not contain enough elements or if the resulting time is out of range, mmkkttiimmee(()) returns -1. ssttrrffttiimmee(([_f_o_r_m_a_t [,, _t_i_m_e_s_t_a_m_p]])) Formats _t_i_m_e_s_t_a_m_p according to the specification in _f_o_r_m_a_t_. The _t_i_m_e_s_t_a_m_p should be of the same form as returned by ssyyssttiimmee(()). If _t_i_m_e_s_t_a_m_p is missing, the current time of day is used. If _f_o_r_m_a_t is missing, a default format equivalent to the output of _d_a_t_e(1) is used. See the spec ification for the ssttrrffttiimmee(()) function in ANSI C for the format conversions that are guaranteed to be available. A public-domain version of _s_t_r_f_t_i_m_e(3) and a man page for it come with _g_a_w_k; if that version was used to build _g_a_w_k, then all of the conversions described in that man page are available to _g_a_w_k_. ssyyssttiimmee(()) Returns the current time of day as the number of seconds since the Epoch (1970-01-01 00:00:00 UTC on POSIX systems). BBiitt MMaanniippuullaattiioonnss FFuunnccttiioonnss Starting with version 3.1 of _g_a_w_k, the following bit manipulation functions are available. They work by con verting double-precision floating point values to uunnssiiggnneedd lloonngg integers, doing the operation, and then converting the result back to floating point. The functions are: aanndd((_v_1,, _v_2)) Return the bitwise AND of the values provided by _v_1 and _v_2. ccoommppll((_v_a_l)) Return the bitwise complement of _v_a_l. llsshhiifftt((_v_a_l,, _c_o_u_n_t)) Return the value of _v_a_l, shifted left by _c_o_u_n_t bits. oorr((_v_1,, _v_2)) Return the bitwise OR of the values provided by _v_1 and _v_2. rrsshhiifftt((_v_a_l,, _c_o_u_n_t)) Return the value of _v_a_l, shifted right by _c_o_u_n_t bits. xxoorr((_v_1,, _v_2)) Return the bitwise XOR of the values provided by _v_1 and _v_2. IInntteerrnnaattiioonnaalliizzaattiioonn FFuunnccttiioonnss Starting with version 3.1 of _g_a_w_k, the following functions may be used from within your AWK program for translating strings at run-time. For full details, see _G_A_W_K_: _E_f_f_e_c_ _t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g. bbiinnddtteexxttddoommaaiinn((_d_i_r_e_c_t_o_r_y [,, _d_o_m_a_i_n])) Specifies the directory where _g_a_w_k looks for the ..mmoo files, in case they will not or cannot be placed in the ``standard'' locations (e.g., during testing). It returns the directory where _d_o_m_a_i_n is ``bound.'' The default _d_o_m_a_i_n is the value of TTEEXXTTDDOOMMAAIINN. If _d_i_r_e_c_t_o_r_y is the null string (""""), then bbiinnddtteexxttddoo mmaaiinn(()) returns the current binding for the given _d_o_m_a_i_n. ddccggeetttteexxtt((_s_t_r_i_n_g [,, _d_o_m_a_i_n [,, _c_a_t_e_g_o_r_y]])) Returns the translation of _s_t_r_i_n_g in text domain _d_o_m_a_i_n for locale category _c_a_t_e_g_o_r_y. The default value for _d_o_m_a_i_n is the current value of TTEEXXTTDDOO MMAAIINN. The default value for _c_a_t_e_g_o_r_y is ""LLCC__MMEESS SSAAGGEESS"". If you supply a value for _c_a_t_e_g_o_r_y, it must be a string equal to one of the known locale categories described in _G_A_W_K_: _E_f_f_e_c_t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g. You must also supply a text domain. Use TTEEXXTTDDOOMMAAIINN if you want to use the current domain. ddccnnggeetttteexxtt((_s_t_r_i_n_g_1 , _s_t_r_i_n_g_2 , _n_u_m_b_e_r [,, _d_o_m_a_i_n [,, _c_a_t_e_ _g_o_r_y]])) Returns the plural form used for _n_u_m_b_e_r of the translation of _s_t_r_i_n_g_1 and _s_t_r_i_n_g_2 in text domain _d_o_m_a_i_n for locale category _c_a_t_e_g_o_r_y. The default value for _d_o_m_a_i_n is the current value of TTEEXXTTDDOO MMAAIINN. The default value for _c_a_t_e_g_o_r_y is ""LLCC__MMEESS SSAAGGEESS"". If you supply a value for _c_a_t_e_g_o_r_y, it must be a string equal to one of the known locale categories described in _G_A_W_K_: _E_f_f_e_c_t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g. You must also supply a text domain. Use TTEEXXTTDDOOMMAAIINN if you want to use the current domain. UUSSEERR--DDEEFFIINNEEDD FFUUNNCCTTIIOONNSS Functions in AWK are defined as follows: ffuunnccttiioonn _n_a_m_e((_p_a_r_a_m_e_t_e_r _l_i_s_t)) {{ _s_t_a_t_e_m_e_n_t_s }} Functions are executed when they are called from within expressions in either patterns or actions. Actual parame ters supplied in the function call are used to instantiate the formal parameters declared in the function. Arrays are passed by reference, other variables are passed by value. Since functions were not originally part of the AWK lan guage, the provision for local variables is rather clumsy: They are declared as extra parameters in the parameter list. The convention is to separate local variables from real parameters by extra spaces in the parameter list. For example: ffuunnccttiioonn ff((pp,, qq,, aa,, bb)) ## aa aanndd bb aarree llooccaall {{ ...... }} //aabbcc// {{ ...... ;; ff((11,, 22)) ;; ...... }} The left parenthesis in a function call is required to immediately follow the function name, without any inter vening white space. This is to avoid a syntactic ambigu ity with the concatenation operator. This restriction does not apply to the built-in functions listed above. Functions may call each other and may be recursive. Func tion parameters used as local variables are initialized to the null string and the number zero upon function invoca tion. Use rreettuurrnn _e_x_p_r to return a value from a function. The return value is undefined if no value is provided, or if the function returns by "falling off" the end. If ----lliinntt has been provided, _g_a_w_k warns about calls to undefined functions at parse time, instead of at run time. Calling an undefined function at run time is a fatal error. The word ffuunncc may be used in place of ffuunnccttiioonn. DDYYNNAAMMIICCAALLLLYY LLOOAADDIINNGG NNEEWW FFUUNNCCTTIIOONNSS Beginning with version 3.1 of _g_a_w_k, you can dynamically add new built-in functions to the running _g_a_w_k inter preter. The full details are beyond the scope of this manual page; see _G_A_W_K_: _E_f_f_e_c_t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g for the details. eexxtteennssiioonn((_o_b_j_e_c_t,, _f_u_n_c_t_i_o_n)) Dynamically link the shared object file named by _o_b_j_e_c_t, and invoke _f_u_n_c_t_i_o_n in that object, to perform initialization. These should both be pro vided as strings. Returns the value returned by _f_u_n_c_t_i_o_n. TThhiiss ffuunnccttiioonn iiss pprroovviiddeedd aanndd ddooccuummeenntteedd iinn _G_A_W_K_: _E_f_f_e_c_ _t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g,, bbuutt eevveerryytthhiinngg aabboouutt tthhiiss ffeeaattuurree iiss lliikkeellyy ttoo cchhaannggee iinn tthhee nneexxtt rreelleeaassee.. WWee SSTTRROONNGGLLYY rreeccoomm mmeenndd tthhaatt yyoouu ddoo nnoott uussee tthhiiss ffeeaattuurree ffoorr aannyytthhiinngg tthhaatt yyoouu aarreenn''tt wwiilllliinngg ttoo rreeddoo.. SSIIGGNNAALLSS _p_g_a_w_k accepts two signals. SSIIGGUUSSRR11 causes it to dump a profile and function call stack to the profile file, which is either aawwkkpprrooff..oouutt, or whatever file was named with the ----pprrooffiillee option. It then continues to run. SSIIGGHHUUPP causes it to dump the profile and function call stack and then exit. EEXXAAMMPPLLEESS Print and sort the login names of all users: BBEEGGIINN {{ FFSS == ""::"" }} {{ pprriinntt $$11 || ""ssoorrtt"" }} Count lines in a file: {{ nnlliinneess++++ }} EENNDD {{ pprriinntt nnlliinneess }} Precede each line by its number in the file: {{ pprriinntt FFNNRR,, $$00 }} Concatenate and line number (a variation on a theme): {{ pprriinntt NNRR,, $$00 }} IINNTTEERRNNAATTIIOONNAALLIIZZAATTIIOONN String constants are sequences of characters enclosed in double quotes. In non-English speaking environments, it is possible to mark strings in the AWK program as requir ing translation to the native natural language. Such strings are marked in the AWK program with a leading underscore ("_"). For example, ggaawwkk ''BBEEGGIINN {{ pprriinntt ""hheelllloo,, wwoorrlldd"" }}'' always prints hheelllloo,, wwoorrlldd. But, ggaawwkk ''BBEEGGIINN {{ pprriinntt __""hheelllloo,, wwoorrlldd"" }}'' might print bboonnjjoouurr,, mmoonnddee in France. There are several steps involved in producing and running a localizable AWK program. 1. Add a BBEEGGIINN action to assign a value to the TTEEXXTTDDOOMMAAIINN variable to set the text domain to a name associated with your program. BBEEGGIINN {{ TTEEXXTTDDOOMMAAIINN == ""mmyypprroogg"" }} This allows _g_a_w_k to find the ..mmoo file associated with your program. Without this step, _g_a_w_k uses the mmeess ssaaggeess text domain, which likely does not contain translations for your program. 2. Mark all strings that should be translated with lead ing underscores. 3. If necessary, use the ddccggeetttteexxtt(()) and/or bbiinnddtteexxttddoo mmaaiinn(()) functions in your program, as appropriate. 4. Run ggaawwkk ----ggeenn--ppoo --ff mmyypprroogg..aawwkk >> mmyypprroogg..ppoo to gener ate a ..ppoo file for your program. 5. Provide appropriate translations, and build and install a corresponding ..mmoo file. The internationalization features are described in full detail in _G_A_W_K_: _E_f_f_e_c_t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g. PPOOSSIIXX CCOOMMPPAATTIIBBIILLIITTYY A primary goal for _g_a_w_k is compatibility with the POSIX standard, as well as with the latest version of UNIX _a_w_k. To this end, _g_a_w_k incorporates the following user visible features which are not described in the AWK book, but are part of the Bell Laboratories version of _a_w_k, and are in the POSIX standard. The book indicates that command line variable assignment happens when _a_w_k would otherwise open the argument as a file, which is after the BBEEGGIINN block is executed. How ever, in earlier implementations, when such an assignment appeared before any file names, the assignment would hap pen _b_e_f_o_r_e the BBEEGGIINN block was run. Applications came to depend on this "feature." When _a_w_k was changed to match its documentation, the --vv option for assigning variables before program execution was added to accommodate applica tions that depended upon the old behavior. (This feature was agreed upon by both the Bell Laboratories and the GNU developers.) The --WW option for implementation specific features is from the POSIX standard. When processing arguments, _g_a_w_k uses the special option "--" to signal the end of arguments. In compatibility mode, it warns about but otherwise ignores undefined options. In normal operation, such arguments are passed on to the AWK program for it to process. The AWK book does not define the return value of ssrraanndd(()). The POSIX standard has it return the seed it was using, to allow keeping track of random number sequences. Therefore ssrraanndd(()) in _g_a_w_k also returns its current seed. Other new features are: The use of multiple --ff options (from MKS _a_w_k); the EENNVVIIRROONN array; the \\aa, and \\vv escape sequences (done originally in _g_a_w_k and fed back into the Bell Laboratories version); the ttoolloowweerr(()) and ttoouuppppeerr(()) built-in functions (from the Bell Laboratories version); and the ANSI C conversion specifications in pprriinnttff (done first in the Bell Laboratories version). HHIISSTTOORRIICCAALL FFEEAATTUURREESS There are two features of historical AWK implementations that _g_a_w_k supports. First, it is possible to call the lleennggtthh(()) built-in function not only with no argument, but even without parentheses! Thus, aa == lleennggtthh ## HHoollyy AAllggooll 6600,, BBaattmmaann!! is the same as either of aa == lleennggtthh(()) aa == lleennggtthh(($$00)) This feature is marked as "deprecated" in the POSIX stan dard, and _g_a_w_k issues a warning about its use if ----lliinntt is specified on the command line. The other feature is the use of either the ccoonnttiinnuuee or the bbrreeaakk statements outside the body of a wwhhiillee, ffoorr, or ddoo loop. Traditional AWK implementations have treated such usage as equivalent to the nneexxtt statement. _G_a_w_k supports this usage if ----ttrraaddiittiioonnaall has been specified. GGNNUU EEXXTTEENNSSIIOONNSS _G_a_w_k has a number of extensions to POSIX _a_w_k. They are described in this section. All the extensions described here can be disabled by invoking _g_a_w_k with the ----ttrraaddii ttiioonnaall option. The following features of _g_a_w_k are not available in POSIX _a_w_k. No path search is performed for files named via the --ff option. Therefore the AAWWKKPPAATTHH environment variable is not special. The \\xx escape sequence. (Disabled with ----ppoossiixx.) The fffflluusshh(()) function. (Disabled with ----ppoossiixx.) The ability to continue lines after ?? and ::. (Disabled with ----ppoossiixx.) Octal and hexadecimal constants in AWK programs. The AARRGGIINNDD, BBIINNMMOODDEE, EERRRRNNOO, LLIINNTT, RRTT and TTEEXXTTDDOOMMAAIINN variables are not special. The IIGGNNOORREECCAASSEE variable and its side-effects are not available. The FFIIEELLDDWWIIDDTTHHSS variable and fixed-width field split ting. The PPRROOCCIINNFFOO array is not available. The use of RRSS as a regular expression. The special file names available for I/O redirection are not recognized. The ||&& operator for creating co-processes. The ability to split out individual characters using the null string as the value of FFSS, and as the third argu ment to sspplliitt(()). The optional second argument to the cclloossee(()) function. The optional third argument to the mmaattcchh(()) function. The ability to use positional specifiers with pprriinnttff and sspprriinnttff(()). The use of ddeelleettee _a_r_r_a_y to delete the entire contents of an array. The use of nneexxttffiillee to abandon processing of the current input file. The aanndd(()), aassoorrtt(()), bbiinnddtteexxttddoommaaiinn(()), ccoommppll(()), ddccggeett tteexxtt(()), ggeennssuubb(()), llsshhiifftt(()), mmkkttiimmee(()), oorr(()), rrsshhiifftt(()), ssttrrffttiimmee(()), ssttrrttoonnuumm(()), ssyyssttiimmee(()) and xxoorr(()) functions. Localizable strings. Adding new built-in functions dynamically with the eexxtteennssiioonn(()) function. The AWK book does not define the return value of the cclloossee(()) function. _G_a_w_k's cclloossee(()) returns the value from _f_c_l_o_s_e(3), or _p_c_l_o_s_e(3), when closing an output file or pipe, respectively. It returns the process's exit status when closing an input pipe. The return value is -1 if the named file, pipe or co-process was not opened with a redi rection. When _g_a_w_k is invoked with the ----ttrraaddiittiioonnaall option, if the _f_s argument to the --FF option is "t", then FFSS is set to the tab character. Note that typing ggaawwkk --FF\\tt ...... simply causes the shell to quote the "t,", and does not pass "\t" to the --FF option. Since this is a rather ugly special case, it is not the default behavior. This behavior also does not occur if ----ppoossiixx has been specified. To really get a tab character as the field separator, it is best to use single quotes: ggaawwkk --FF''\\tt'' ....... EENNVVIIRROONNMMEENNTT VVAARRIIAABBLLEESS The AAWWKKPPAATTHH environment variable can be used to provide a list of directories that _g_a_w_k searches when looking for files named via the --ff and ----ffiillee options. If PPOOSSIIXXLLYY__CCOORRRREECCTT exists in the environment, then _g_a_w_k behaves exactly as if ----ppoossiixx had been specified on the command line. If ----lliinntt has been specified, _g_a_w_k issues a warning message to this effect. SSEEEE AALLSSOO _e_g_r_e_p(1), _g_e_t_p_i_d(2), _g_e_t_p_p_i_d(2), _g_e_t_p_g_r_p(2), _g_e_t_u_i_d(2), _g_e_t_e_u_i_d(2), _g_e_t_g_i_d(2), _g_e_t_e_g_i_d(2), _g_e_t_g_r_o_u_p_s(2) _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, Alfred V. Aho, Brian W. Kernighan, Peter J. Weinberger, Addison-Wesley, 1988. ISBN 0-201-07981-X. _G_A_W_K_: _E_f_f_e_c_t_i_v_e _A_W_K _P_r_o_g_r_a_m_m_i_n_g, Edition 3.0, published by the Free Software Foundation, 2001. BBUUGGSS The --FF option is not necessary given the command line variable assignment feature; it remains only for backwards compatibility. Syntactically invalid single character programs tend to overflow the parse stack, generating a rather unhelpful message. Such programs are surprisingly difficult to diagnose in the completely general case, and the effort to do so really is not worth it. AAUUTTHHOORRSS The original version of UNIX _a_w_k was designed and imple mented by Alfred Aho, Peter Weinberger, and Brian Kernighan of Bell Laboratories. Brian Kernighan continues to maintain and enhance it. Paul Rubin and Jay Fenlason, of the Free Software Founda tion, wrote _g_a_w_k, to be compatible with the original ver sion of _a_w_k distributed in Seventh Edition UNIX. John Woods contributed a number of bug fixes. David Trueman, with contributions from Arnold Robbins, made _g_a_w_k compati ble with the new version of UNIX _a_w_k. Arnold Robbins is the current maintainer. The initial DOS port was done by Conrad Kwok and Scott Garfinkle. Scott Deifik is the current DOS maintainer. Pat Rankin did the port to VMS, and Michal Jaegermann did the port to the Atari ST. The port to OS/2 was done by Kai Uwe Rommel, with contributions and help from Darrel Hankerson. Fred Fish supplied support for the Amiga, Stephen Davies provided the Tandem port, and Martin Brown provided the BeOS port. VVEERRSSIIOONN IINNFFOORRMMAATTIIOONN This man page documents _g_a_w_k, version 3.1.0. BBUUGG RREEPPOORRTTSS If you find a bug in _g_a_w_k, please send electronic mail to bbuugg--ggaawwkk@@ggnnuu..oorrgg. Please include your operating system and its revision, the version of _g_a_w_k (from ggaawwkk ----vveerr ssiioonn), what C compiler you used to compile it, and a test program and data that are as small as possible for repro ducing the problem. Before sending a bug report, please do two things. First, verify that you have the latest version of _g_a_w_k. Many bugs (usually subtle ones) are fixed at each release, and if yours is out of date, the problem may already have been solved. Second, please read this man page and the reference manual carefully to be sure that what you think is a bug really is, instead of just a quirk in the lan guage. Whatever you do, do NNOOTT post a bug report in ccoommpp..llaanngg..aawwkk. While the _g_a_w_k developers occasionally read this newsgroup, posting bug reports there is an unre liable way to report bugs. Instead, please use the elec tronic mail addresses given above. AACCKKNNOOWWLLEEDDGGEEMMEENNTTSS Brian Kernighan of Bell Laboratories provided valuable assistance during testing and debugging. We thank him. CCOOPPYYIINNGG PPEERRMMIISSSSIIOONNSS Copyright 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2001, 2002 Free Software Foundation, Inc. Permission is granted to make and distribute verbatim copies of this manual page provided the copyright notice and this permission notice are preserved on all copies. Permission is granted to copy and distribute modified ver sions of this manual page under the conditions for verba tim copying, provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one. Permission is granted to copy and distribute translations of this manual page into another language, under the above conditions for modified versions, except that this permis sion notice may be stated in a translation approved by the Foundation. Free Software Foundation Apr 16 2002 GAWK(1)