1 Introduction
2 Ground Rules

Building a File System
3 File Systems
4 File Content Data Structure
5 Allocation Cluster Manager
6 Exceptions and Emancipation
7 Base Classes, Testing, and More
8 File Meta Data
9 Native File Class
10 Our File System
11 Allocation Table
12 File System Support Code
13 Initializing the File System
14 Contiguous Files
15 Rebuilding the File System
16 Native File System Support Methods
17 Lookups, Wildcards, and Unicode, Oh My
18 Finishing the File System Class

The Init Program
19 Hardware Abstraction and UOS Architecture
20 Init Command Mode
21 Using Our File System
22 Hardware and Device Lists
23 Fun with Stores: Partitions
24 Fun with Stores: RAID
25 Fun with Stores: RAM Disks
26 Init wrap-up

The Executive
27 Overview of The Executive
28 Starting the Kernel
29 The Kernel
30 Making a Store Bootable
31 The MMC
32 The HMC
33 Loading the components
34 Using the File Processor
35 Symbols and the SSC
36 The File Processor and Device Management
37 The File Processor and File System Management
38 Finishing Executive Startup

Users and Security
39 Introduction to Users and Security
40 More Fun With Stores: File Heaps
41 File Heaps, part 2
42 SysUAF
43 TUser
44 SysUAF API

Terminal I/O
45 Shells and UCL
46 UOS API, the Application Side
47 UOS API, the Executive Side
48 I/O Devices
49 Streams
50 Terminal Output Filters
51 The TTerminal Class
52 Handles
53 Putting it All Together
54 Getting Terminal Input
55 QIO
56 Cooking Terminal Input
57 Putting it all together, part 2
58 Quotas and I/O

UCL
59 UCL Basics
60 Symbol Substitution
61 Command execution
62 Command execution, part 2
63 Command Abbreviation
64 ASTs
65 Expressions, Part 1
66 Expressions, Part 2: Support code
67 Expressions, part 3: Parsing
68 SYS_GETJPIW and SYS_TRNLNM
69 Expressions, part 4: Evaluation

UCL Lexical Functions
70 PROCESS_SCAN
71 PROCESS_SCAN, Part 2
72 TProcess updates
73 Unicode revisted
74 Lexical functions: F$CONTEXT
75 Lexical functions: F$PID
76 Lexical Functions: F$CUNITS
77 Lexical Functions: F$CVSI and F$CVUI
78 UOS Date and Time Formatting
79 Lexical Functions: F$CVTIME
80 LIB_CVTIME
81 Date/Time Contexts
82 SYS_GETTIM, LIB_Get_Timestamp, SYS_ASCTIM, and LIB_SYS_ASCTIM
83 Lexical Functions: F$DELTA_TIME
84 Lexical functions: F$DEVICE
85 SYS_DEVICE_SCAN
86 Lexical functions: F$DIRECTORY
87 Lexical functions: F$EDIT and F$ELEMENT
88 Lexical functions: F$ENVIRONMENT
89 SYS_GETUAI
90 Lexical functions: F$EXTRACT and F$IDENTIFIER
91 LIB_FAO and LIB_FAOL
92 LIB_FAO and LIB_FAOL, part 2
93 Lexical functions: F$FAO
94 File Processing Structures
95 Lexical functions: F$FILE_ATTRIBUTES
96 SYS_DISPLAY
97 Lexical functions: F$GETDVI
98 Parse_GetDVI
99 GetDVI
100 GetDVI, part 2
101 GetDVI, part 3
102 Lexical functions: F$GETJPI
103 GETJPI
104 Lexical functions: F$GETSYI
105 GETSYI
106 Lexical functions: F$INTEGER, F$LENGTH, F$LOCATE, and F$MATCH_WILD
107 Lexical function: F$PARSE
108 FILESCAN
109 SYS_PARSE
110 Lexical Functions: F$MODE, F$PRIVILEGE, and F$PROCESS
111 File Lookup Service
112 Lexical Functions: F$SEARCH
113 SYS_SEARCH
114 F$SETPRV and SYS_SETPRV
115 Lexical Functions: F$STRING, F$TIME, and F$TYPE
116 More on symbols
117 Lexical Functions: F$TRNLNM
118 SYS_TRNLNM, Part 2
119 Lexical functions: F$UNIQUE, F$USER, and F$VERIFY
120 Lexical functions: F$MESSAGE
121 TUOS_File_Wrapper
122 OPEN, CLOSE, and READ system services

UCL Commands
123 WRITE
124 Symbol assignment
125 The @ command
126 @ and EXIT
127 CRELNT system service
128 DELLNT system service
129 IF...THEN...ELSE
130 Comments, labels, and GOTO
131 GOSUB and RETURN
132 CALL, SUBROUTINE, and ENDSUBROUTINE
133 ON, SET {NO}ON, and error handling
134 INQUIRE
135 SYS_WRITE Service
136 OPEN
137 CLOSE
138 DELLNM system service
139 READ
140 Command Recall
141 RECALL
142 RUN
143 LIB_RUN
144 The Data Stream Interface
145 Preparing for execution
146 EOJ and LOGOUT
147 SYS_DELPROC and LIB_GET_FOREIGN

CUSPs and utilities
148 The I/O Queue
149 Timers
150 Logging in, part one
151 Logging in, part 2
152 System configuration
153 SET NODE utility
154 UUI
155 SETTERM utility
156 SETTERM utility, part 2
157 SETTERM utility, part 3
158 AUTHORIZE utility
159 AUTHORIZE utility, UI
160 AUTHORIZE utility, Access Restrictions
161 AUTHORIZE utility, Part 4
162 AUTHORIZE utility, Reporting
163 AUTHORIZE utility, Part 6
164 Authentication
165 Hashlib
166 Authenticate, Part 7
167 Logging in, part 3
168 DAY_OF_WEEK, CVT_FROM_INTERNAL_TIME, and SPAWN
169 DAY_OF_WEEK and CVT_FROM_INTERNAL_TIME
170 LIB_SPAWN
171 CREPRC
172 CREPRC, Part 2
173 COPY
174 COPY, part 2
175 COPY, part 3
176 COPY, part 4
177 LIB_Get_Default_File_Protection and LIB_Substitute_Wildcards
178 CREATESTREAM, STREAMNAME, and Set_Contiguous
179 Help Files
180 LBR Services
181 LBR Services, Part 2
182 LIBRARY utility
183 LIBRARY utility, Part 2
184 FS Services
185 FS Services, Part 2
186 Implementing Help
187 HELP
188 HELP, Part 2
189 DMG_Get_Key and LIB_Put_Formatted_Output
190 LIBRARY utility, Part 3
191 Shutting Down UOS
192 SHUTDOWN
193 WAIT
194 SETIMR
195 WAITFR and Scheduling
196 REPLY, OPCOM, and Mailboxes
197 REPLY utility
198 Mailboxes

Glossary/Index


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Lexical functions: F$INTEGER, F$LENGTH, F$LOCATE, and F$MATCH_WILD

The next lexical functions are short, so we'll combine them into a single article rather than four tiny articles. I should also note that we will be skipping the F$LICENSE lexical function for now and we'll cover that with licenses in a future article.

The F$INTEGER lexical function is used in DCL to convert a string to an integer. Because, in UCL, symbols are untyped, this function basically returns the passed parameter. One thing it does is convert a non-numeric string into a 0 or 1. Here is the definition.

F$INTEGER returns the integer equivalent of the result of the passed expression.

Format
F$INTEGER( expression )

Return Value
Returns the result of the passed expression as an integer.

Arguments
expression

Specifies the expression or value to be evaluated. Integer values are returned as an integer.
If the expression evaluates to a string, the result is convered to an integer. If the string does not contain a valid integer, the function returns 1 if the string begins with T, t, Y, or y. Otherwise it returns 0.

Example
$ A = F$INTEGER("12")
The symbol A would be set to 12 by this script.

        Function_INTEGER : begin
                               if( Missing_Parentheses( '(' ) ) then
                               begin
                                   exit ;
                               end ;
                               if( Parse_Integer( Err, Context ) ) then
                               begin
                                   exit ;
                               end ;
                               if( Missing_Parentheses( ')' ) ) then
                               begin
                                   exit ;
                               end ;
                               S := Context ;
                           end ;
We add this code to Function_Reference.

function Parse_Integer( var Err : integer ; var Context : string ) : boolean ;

var Itm : string ;

begin
    // Setup...
    Result := False ; // Assume no problems
    Context := '' ;

    // Get item...
    Itm := UCL_Strtoint( Get_Parameter( Err, Context ) ) ;
    if( Err = 0 ) then
    begin
        Context := Itm ;
    end ;
end ;
This function gets the next parameter and, if we have no error, we return the value. The value is converted via UCL_Strtoint, which handles strings that do not contain valid integer values.


F$LENGTH returns the length of the specified string. If the parameter is an integer, this returns the length of that integer as a string.

Format
F$LENGTH( value )

Return Value
Returns the length of the passed value.

Arguments
value

Specifies the value whose length to return.

Example
$ A = F$LENGTH("Hello")
The symbol A would be set to 5 by this script.

        Function_LENGTH : begin
                               if( Missing_Parentheses( '(' ) ) then
                               begin
                                   exit ;
                               end ;
                               if( Parse_Length( Err, Context ) ) then
                               begin
                                   exit ;
                               end ;
                               if( Missing_Parentheses( ')' ) ) then
                               begin
                                   exit ;
                               end ;
                               S := Context ;
                          end ;
We add this code to the Function_Reference routine.

function Parse_Length( var Err : integer ; var Context : string ) : boolean ;

var Itm : string ;

begin
    // Setup...
    Result := False ; // Assume no problems
    Context := '' ;

    // Get item...
    Itm := Get_Parameter( Err, Context ) ;
    if( Err = 0 ) then
    begin
        Context := inttostr( length( Itm ) ) ;
    end ;
end ;
This function obtains the parameter and returns the length of that string.


F$LOCATE locates the specified substring in another string and returns the offset of the substring within the other string. Positions are zero-based, thus the first character is at position 0. If the substring is not found, the length of the string is returned.

Format
F$LOCATE( substring, string )

Return Value
An integer value relative to position 0 from the beginning (leftmost) character of the string. If the substring is not found in the string, the string length is returned (the offset immediately after the last offset in the string).

Arguments
substring

Specifies the string to search for within the next parameter value.

string

Specifies the string to search for the substring.

Example
$ A = F$LOCATE("Wo","Hello World")
This script locates the position of "Wo" within "Hello World". The symbol A would be set to 6 in this case.

        Function_LOCATE : begin
                              if( Missing_Parentheses( '(' ) ) then
                              begin
                                  exit ;
                              end ;
                              if( Parse_Locate( Err, Context ) ) then
                              begin
                                  exit ;
                              end ;
                              if( Missing_Parentheses( ')' ) ) then
                              begin
                                  exit ;
                              end ;
                              S := Context ;
                          end ;
We add this code to the Function_Reference routine.

function Parse_Locate( var Err : integer ; var Context : string ) : boolean ;

var I : integer ;
    Str, Substr : string ;

begin
    // Setup...
    Result := False ; // Assume no problems
    Context := '' ;

    // Get items...
    Substr := Get_Parameter( Err, Context ) ;
    if( Err <> 0 ) then
    begin
        exit ;
    end ;
    if( Missing_Comma( Err ) ) then
    begin
        exit ;
    end ;
    Str := Get_Parameter( Err, Context ) ;
    if( Err <> 0 ) then
    begin
        exit ;
    end ;

    // Process result...
    I := pos( Substr, Str ) - 1 ;
    if( I < 0 ) then // Not found
    begin
        I := length( Str ) ;
    end ;
    Context := inttostr( I ) ;
end ;
This function gets the parameters and then uses the pos function to get the location. The pos function returns a 1-based index. Since this lexical function returns a 0-based index, we subtract 1 from the result. pos returns 0 if the substring isn't found, which means I will be -1. So in that case, we set the result to the length of the string.


F$MATCH_WILD performs a wildcard match between one string and a pattern string. TRUE is returned if the strings match.

Format
F$MATCH_WILD( string, pattern )

Return Value
Returns the result of wildcard comparison as TRUE or FALSE.

Arguments
string

Specifies the string to match to the wildcard pattern.

pattern

Specifies the wildcard pattern to match with the string.

Example
$ A = F$MATCH_WILD("Hello World","Hello*")
The symbol A would be set to TRUE in this case.

        Function_MATCH_WILD : begin
                                  if( Missing_Parentheses( '(' ) ) then
                                  begin
                                      exit ;
                                  end ;
                                  if( Parse_Match_Wild( Err, Context ) ) then
                                  begin
                                      exit ;
                                  end ;
                                  if( Missing_Parentheses( ')' ) ) then
                                  begin
                                      exit ;
                                  end ;
                                  S := Context ;
                              end ;
We add this code to the Function_Reference function.

function Parse_Match_Wild( var Err : integer ; var Context : string ) : boolean ;

var I : integer ;
    Str, Pattern : string ;

begin
    // Setup...
    Result := False ; // Assume no problems
    Context := '' ;

    // Get items...
    Str := Get_Parameter( Err, Context ) ;
    if( Err <> 0 ) then
    begin
        exit ;
    end ;
    if( Missing_Comma( Err ) ) then
    begin
        exit ;
    end ;
    Pattern := Get_Parameter( Err, Context ) ;
    if( Err <> 0 ) then
    begin
        exit ;
    end ;

    if( WC_Match( Pattern, Str, 3 ) ) then
    begin
        Context := 'TRUE' ;
    end else
    begin
        Context := 'FALSE' ;
    end ;
end ;
This function gets the parameters and then uses the WC_Match function to compare the two strings as UTF-8 values. We discussed WC_Match in article 17.

In the next article, we will look at the next lexcial function.

 

Copyright © 2020 by Alan Conroy. This article may be copied in whole or in part as long as this copyright is included.