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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 199 BRKTHRU 200 OPCOM 201 Mailbox Services 202 Mailboxes, Part 2 203 DEFINE 204 CRELNM 205 DISABLE 206 STOP 207 OPCCRASH and SHUTDOWN 208 APPEND Glossary/Index Downloads |
OPEN The only thing missing from UCL at this point that prevents its use as a general purpose scripting language is some level of file handling. In the next couple articles, we will address this. With the addition of file I/O, we could even write a simple text file editor in UCL. I'm not going to, but it could be done. I'll leave it as an exercise for the reader. Granted, UCL will only support text files at present. When we add RMS file support in the future, we will revisit UCL file I/O to support other file formats. For now, we will check RMS-specific switches for validity, but otherwise ignore them. We will store the file instance references in UOS symbols. Similarly to the search contexts we've talked about in the past, UCL will keep a list of open files that can be checked when a symbol is used as a file identifier. We discussed the WRITE command a few articles ago, and it already supports file I/O. In this and the next few articles, we will discuss the OPEN, READ, and CLOSE commands. Here is the user documentation for OPEN: OPEN Opens or creates a file for reading and/or writing.
Format OPEN symbol{:} filespec
Parameters symbol
filespec
Description Files can be opened for reading and/or writing, and they can be created if they don't exist. Once open, the file can be used in the READ and WRITE commands. The CLOSE command is used to close an open file. The files will remain open until explicitly closed or the process logs out. Note that if a command file exits with an error, any files it opened and did not explicitly close will remain open.
Qualifiers /APPEND
/ERROR=label
/READ (default)
/{NO}SHARE{=option}
/WRITE
Example
Process routine.
Switch_Match is covered below.
Default_Filespec to default the current
device, directory path, and extension.
FAB_V_MXV
in the flags. This flag indicates to create a new file. We open/create the file
and if that fails (F is nil), we set the exception and exit.
Name_Match, which we covered in the past. It handles the optional
equal sign (=) and parameter and returns true if a match, and if a parameter is
provided, it returns the parameter via Options.
TUOS_FiP.Open_File method. The new
code is between the "NEW" comments. When creating a new file, we have to check the
protection code of the directory in which we are creating the file. If the file
already exists, we also have to check the protection code of the existing file. If
protection isn't violated, we delete the existing file and then drop through to the
file creation code. We will be revisiting this code in the future to handle issues
of backups and versioning.
In the next article, we will look at the CLOSE command.
Copyright © 2021 by Alan Conroy. This article may be copied in whole or in part as long as this copyright is included. |