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Text File | 1990-11-04 | 13.1 KB | 274 lines

QTAwk A new shareware program, QTAwk. The program is a "derivative" of "The Awk Programming Language." Four versions of the program exist for the IBM PC and clones depending on the h/w configuration: 8086/8088, or 80286+ and with or without 80x87 numeric co-processor. The QTAwk package contains many complete and sample utilities which run under QTAwk. ---------------------------------------------------------------------------- The major differences between QTAwk and Awk are summarized below: Major differences between QTAwk (version 4.20) and Awk. 1. Expanded Regular Expressions All of the Awk regular expression operators are allowed plus the following: a) complemented character class using the Awk notation, '[^...]', as well as the Awk/QTAwk and C logical negation operator, '[!...]'. b) Matched character classes, '[#...]'. These classes are used in pairs. The position of the character matched in the first class of the pair, determines the character which must match in the position occupied by the second class of the pair. c) Look-ahead Operator. r@t regular expression r is matched only when followed by regular expression t. d) Repetition Operator. r{n1,n2} at least n1 and up to n2 repetitions of regular expression r. 1 <= n1 <= n2 e) Named Expressions. {named_expr} is replaced by the string value of the corrsponding variable. 2. Consistent statement termination syntax. The QTAwk Utility Creation Tool utilizes the semi-colon, ';', to terminate all statements. The practice in Awk of using newlines to "sometimes" terminate statements is no longer allowed. 3. Expanded Operator Set The Awk set of operators has been changed to more closely match those of C. The Awk match operator, '~', has been changed to '~~' so that the similarity between the match operators, '~~' and '!~', to the equality operators, '==' and '!=", is complete. The single tilde symbol, '~', reverts to the C one's complement operator, an addition to the operator set over Awk. The introduction of the explicit string concatenation operator. The remaining "new" operators to QTAwk are: Operation Operator --------- -------- tag $$ one's complement ~ concatenation ∩ ( ASCII 239, 0xef character) shift left/right << >> matching ~~ !~ bit-wise AND & bit-wise XOR @ bit-wise OR | sequence , The carot, '^', remains as the expoentiation operator. The symbol '@' is used for the exclusive OR operator. 4. Expanded set of recognized constants in QTAwk utilities: a) decimal integers, b) octal integers, c) hexadecimal integers, d) character constants, and e) floating point constants. 5. Expanded Pre-defined patterns giving more control: a) INIITAL - similar to BEGIN. Actions executed after opening each input file and before reading first record. b) FINAL - similar to END. Actions executed after reading last record of each input file and before closing file. c) NOMATCH - actions executed for each input record for which no pattern was matched. d) GROUP - used to group multiple regular expressions for search optimization. Can speed search by a factor of six. 6. True multi-dimensional arrays The use of the comma in index expressions to simulate multiple array indices is no longer supported. True multiple indices are supported. Indexing is in the C manner, 'a[i1][i2]'. The SUBSEP built-in variable of AWK has been dropped since it is no longer necessary. 7. Integer array indices as well as string indices Array indices have been expanded to include integers as well as the string indices of Awk. Indices are not automatically converted to strings as in Awk. Thus, for true integer indices, the index ordering follows the numeric sequence with an integer index value of '10' following a value of '2' instead of preceeding it. 8. Arrays integrated into QTAwk QTAwk integrates arrays with arithmetic operators so that the operations are carried out on the entire array. QTAwk also integrates arrays into user-defined functions so that they can be passed to and returned from such functions in a natural and intuitive manner. Awk does not allow returning arrays from user-defined functions or allow arithmetic operators to operate on whole arrays. 9. NEW keywords: a) cycle similar to 'next' except that may use current record in restarting outer pattern matching loop. b) deletea similiar to 'delete' except that ALL array values deleted. c) switch, case, default similiar to C syntax with the allowed 'switch' and 'case' values expanded to include any legal QTAwk expression, evaluated at run-time. The expressions may evaluate to any value including any numeric value, string or regular expression. d) local new keyword to allow the declaration and use of local variables within compound statements, including user-defined functions. Its use in user defined functions instead of the Awk practice of defining excess formal parameters, leads to easier to read and maintain functions. The C 'practice' of allowing initialization in the 'local' statement is followed. e) endfile similar to 'exit'. Simulates end of current input file only, any remaining input files are still processed. 10. Expanded arithmetic functions QTAwk includes 18 built-in arithmetic functions. All of the functions supported by Awk plus the following: a) acos(x) b) asin(x) c) cosh(x) d) fract(x) e) log10(x) f) pi() or pi g) sinh(x) 11. Expanded string functions QTAwk includes 33 built-in string functions. All of the functions supported by Awk plus the following: a) center(s,w) or center(s,w,c) b) copies(s,n) c) deletec(s,p,n) d) insert(s1,s2,p) e) justify(a,n,w) or justify(a,n,w,c) f) overlay(s1,s2,p) g) remove(s,c) h) replace(s) i) sdate(fmt) j) srange(c1,c2) k) srev(s) l) stime(fmt) m) stran(s) or stran(s,st) or stran(s,st,sf) n) strim(s) or strim(s,c) or strim(s,c,d) o) strlwr(s) p) strupr(s) 12. New Miscellaneous functions a) The function 'rotate(a)' is provided to rotate the elements of the array a. b) execute(s) or execute(s,se) or execute(s,se,rf) - execute string s c) execute(a) or execute(a,se) or execute(a,se,rf) - execute array a d) pd_sym - access pre-defined symbols e) ud_sym - access user defined symbols 13. New I/O Functions I/O function syntax has been made consistent with syntax of other functions. The redirection operators, '<', '>' and '>>', and pipeline operator, '|', have been deleted as excessively error prone in expressions. The functional syntax of the 'getline' function has been made identical to that of the other built-in functions. The new functions 'fgetline', 'fprint' and 'fprintf' have been introduced for reading and writing to files other than the current input file. Single Character input functions, 'getc' and 'fgetc' have been added to read files (and the keyboard) a single character at a time. 14. Expanded capability of formatted I/O. The limited output formatting available with the Awk 'printf' function has been expanded by adopting the complete output format specification of the draft ANSI C standard. 15. Use of 'local' keyword The 'local' keyword has been introduced to allow for variables local to user-defined functions (and any compound statement). This expansion makes the Awk practice of defining 'extra' formal parameters no longer necessary. 16. Expanded user-defined functions With the 'local' keyword, QTAwk allows the user to define functions that may accept a variable number of arguments. Functions, such as finding the minimum/maximum of a variable number of variables, are possible with one function rather than defining separate functions for each possible combination of arguments. 17. User controlled trace capability A user controlled statement trace capability has been added. This gives the user a simple to use mechanism to trace utility execution. Rather than adding 'print' statements, merely re-defining the value of a built-in variable will give utility execution trace information, including utility line number. 18. Expanded built-in variable list With 30 built-in variables, QTAwk includes all (with the exception of SUBSEP) of the built-in variables of Awk plus the following: a) _arg_chk - used to determine whether to check number of arguments passed to user-defined functions. b) ARGI - index value in ARGV of next command line argument. Gives more control of command line argument processing. c) CYCLE_COUNT - count number of outer loop cycles with current input record. d) DEGREES - if TRUE, trigonometric functions assume degree values, radians if FALSE. e) ENVIRON - array of environment strings passed to QTAwk f) FALSE - pre-defined with constant value, 0. g) TRUE - predefined with constant value, 1 h) LONGEST_EXP - used to control whether the longest or the first string matching a regular expression is found. j) MAX_CYCLE - maximum number of outer loop cycles permitted with current input record. k) NG - equal to the number of the regular expression in a group matching a string in the current input record. k) RETAIN_FS - if TRUE the original characters separating the fields of the current input record are retained whenever a field is changed, causing the input record to be re-constructed. If FALSE the output field separator, OFS, is used to separate fields in the current input record during reconstruction. The latter practice is the only method available in Awk. l) TRACE - value used to determine utility tracing. m) TRANS_FROM/TRANS_TO - strings used by 'stran' function if second and/or third arguments not specified. n) CLENGTH - similiar to 'RLENGTH' of Awk. Set whenever a 'case' value evaluates to a regular expression. o) CSTART - similiar to 'RSTART' of Awk. Set whenever a 'case' value evaluates to a regular expression. p) MLENGTH - similiar to 'RLENGTH' of Awk. Set whenever a stand-alone regular expression is encountered in evaluting a pattern. q) MSTART - similiar to 'RSTART' of Awk. Set whenever a stand-alone regular expression is encountered in evaluting a pattern. r) vargc - used only in used-defined functions defined with a variable number of arguments. At runtime, set equal to the actual number of variable arguments passed. s) vargv - used only in used-defined functions defined with a variable number of arguments. At runtime, an single dimensioned array with each element set to the argument actually passed. 19. Definition of built-in variable, RS, expanded to mimic the FS built-in variable. For A single character string, the single character becomes the input record separator. If the string is longer than a single character, it is treated as a regular expression, and any string matching the regular expression becomes a record separator. Awk will recognize first character only of RS string as record delimitor. 20. In QTAwk, setting built-in variable, "FILENAME", to another value will change the current input file. Setting the variable in Awk, has no effect on current input file. 21. New character input functions, 'getc' and 'fgetc', can accept keyboard input also. 22. Corrected admitted problems with Awk. The problems mentioned on page 182 of "The Awk Programming Language" have been corrected. Specifically: 1) true multi-dimensional arrays have been implemented, 2) the 'getline' syntax has been made to match that of other functions, 3) declaring local variables in user-defined functions has been corrected, 4) intervening blanks are allowed between the function call name and the opening parenthsis (in fact, under QTAwk it is permissable to have no opening parenthesis or argument list for user-defined functions that have been defined with no formal arguments).