Using Expressions in CI Commands

The CI provides an expression evaluator that supports a large selection of arithmetic operations; number conversions; file information; and string, bit, and variable operations. (Appendix B provides a table of commonly used functions. Refer to the MPE/iX Commands Reference Manual (32650-90003) for a complete list of expression evaluator functions.)

Performing Arithmetic Operations

Standard addition, subtraction, multiplication, and division functions, as well as exponentiation, absolute value, and modulo arithmetic functions, are valid arithmetic operations in the CI. The standard expression symbols are used in the CI as in other programming languages.

The following examples show the common arithmetic symbols used by the CI.

   Description              Example       Result



   Addition                  1 + 3          4

   Subtraction               3 - 1          2

   Multiplication            2 * 4          8

   Division                 16 / 8          2

   Absolute Value          ABS(-3)          3

   Exponentiation              2^3          8

   Multiple Functions    2 * 3 + 6         12

The expression evaluator performs integer algebra. Functions are executed from left to right, in the following order of operations.

Exponentiation and absolute value.
Multiplication and division.
Addition and subtraction.

The following example sets the variable EXP with the result of an expression. Note the order in which the operations are performed.

   :SETVAR A 1

   :SETVAR B 2

   :SETVAR C 3

   :SETVAR D 4

   :SETVAR EXP A+B*C/D

   :SHOWVAR EXP

   EXP = 2

The multiplication and division functions are performed first from left to right. The integer result is added to A. Note that division is an integer function; results are truncated, not rounded.

Parentheses can be inserted to clarify or to alter the logical order of operations. The following example provides the expression from the previous example with parentheses included for clarification.

   :SETVAR EXP A+((B*C/D)

Evaluating Strings

String functions provide a means of analyzing strings. These functions include adding and subtracting characters in a string, determining the length of a string, determining the position of a particular character in a string, adjusting the case of characters, repeating a a character in a string, and removing leading or trailing characters from a string.

Strings are evaluated character by character from left to right. Adding two strings concatenates the contents of the second string to the end of the first.

   :SETVAR ANS "abcd" + "efg"

   :SHOWVAR ANS

   ANS = abcdefg

Subtracting characters from a string deletes the first occurrence of the specified characters from the original string.

   :SETVAR ANS "abcabc" - "ab"

   :SHOWVAR ANS

   ANS = cabc

The case of string data can be altered with the downshift (DWNS) or upshift (UPS) functions. These functions are used in case-sensitive comparisons.

   :SETVAR ANS UPS("abcdEFG")

   :SHOWVAR ANS

   ANS = ABCDEFG



   :SETVAR ANS DWNS("abcdEFG")

   :SHOWVAR ANS

   ANS = abcdefg

The length of a string can be determined with the LEN function.

   :SETVAR ANS LEN("abcdefg")

   :SHOWVAR ANS

   ANS = 7

The RPT function repeats a string a specified number of times. This is often used to pad another string with blanks or zeros.

   :SETVAR ANS RPT("A",3)

   :SHOWVAR ANS

   ANS = AAA

The LTRIM and RTRIM functions trim leading or trailing characters from the left or right of a string. Blanks are trimmed from the string unless a trim character is specified in the command.

   :SETVAR ANS RTRIM("ABC    ") + LTRIM(".....DEF",".")

   :SHOWVAR ANS

   ANS = ABCDEF

ASCII characters can be defined by their ordinal representation. Note that if the parameter of the ordinal function consists of more than one character, the ordinal representation of only the first character is returned. The other characters are ignored.

   :SETVAR ANS ORD("AbcD")

   :SHOWVAR ANS

   ANS = 65

Ordinal numbers can likewise be defined by their ASCII character representation. This is often used for escape sequences and control sequences that have no printable counterpart.

   :SETVAR ANS CHR(65)

   :SHOWVAR ANS

   ANS = A

Performing Bit Operations

Integer data can be evaluated and adjusted by using the bit operations provided with the CI. These include bit shift left (LSL), bit shift right (LSR), and circular shifts (CSL and CSR). Also, logical OR, AND, NOT, and XOR operations are available.

Because AM capability is identified by a 1 in the second bit of the predefined variable HPUSERCAP, either of the following expressions can be used to see if a user has AM capability.

   IF ((HPUSERCAP LSR 30) BAND 1) = 1 THEN ...

   IF ODD(HPUSERCAP LSR 30) THEN ...

Note that the preceding examples show the use of the bit operations. A simpler way of determining if a user has AM capability would be the following method.

   IF POS("AM",HPUSERCAPF) > 0 THEN

   [vellip]

Converting Numbers

Numeric values can be converted from decimal representation to octal or hexadecimal string equivalents. Numeric output is identified by three prefixes: # represents decimal, $ represents hexadecimal, and % represents octal. If no prefix is specified, decimal is assumed.

In the following example, the decimal number 329 is converted to its hexadecimal and octal string representations.

   SETVAR ANS HEX(329)

   SHOWVAR ANS

   ANS = $149



   SETVAR ANS OCTAL(329)

   SHOWVAR ANS

   ANS = %511




	NOTE: The results of converting numbers using the `HEX` and `OCTAL` functions are character strings. The result cannot be used in numeric calculations.

Evaluating File Characteristics

The FINFO function retrieves file specifications for the identified file. This is useful in creating files, verifying that a file exists, or identifying file specifications.

The type of file information requested is identified by a numeric entry or an alias for the numeric entry, similar to the parameters of the FINFO function. Note that aliases are strings and must be enclosed in parentheses. String, boolean, or numeric data is returned depending on the option specified.

FINFO recognizes HFS (hierarchical file system) names and supports the FLABELINFO intrinsic items relating to POSIX. Examples include:

number of hard links
time of last file access
file owner (full user.account name and numeric ID)
file type (directory, symbolic link, pipe, FIFO, device link, etc.)
record type (fixed, root, spool, byte stream, directory, etc.)
file size in bytes
KSAM XL version
device type (disk, tape, port, streams, sockets, etc.)
whether the file has been released.

Refer to New Features of MPE/iX: Using The Hierarchical File System (32650-90351).

The following table provides some of the most commonly used FINFO options, by number and alias, and a description of the results. FINFO passes the name of the file using either MPE syntax (the default) or HFS syntax. You can enter CALC FINFO('.1',0) and receive TRUE as output, and filename in HFS can end in any character.

If MPE syntax, the file name can include password, group, and account specifications. The file name can backreference a file equation and optionally be preceded by an asterisk.

If HFS syntax, the file name must start with either a dot (.) or a slash (/). For files located in HFS directories, traverse directory entries (TD) access is required to all directories specified in the formal design. If there is no TD access, FINFO fails.

If the file can be named using both MPE syntax and HFS syntax (for example, FILEA.MYGROUP.MYACCT and /MYACCT/MYGROUP/FILEA), the file can be either permanent or temporary. If a temporary and a permanent file have the same name, FINFO returns information about the temporary file only. Refer to the MPE/iX Commands Reference Manual (32650-90003) for a complete description of the FINFO options.

Table 4-1 FIFO Specifications

Number	Alias	Data Type	Item Description
0	EXIST	Boolean	Existence of file
1	FILENAME ONLY FNAME FULL FILENAME FULLFNAME FULLY QUALIFIED FILENAME	String	File name
2	GROUP GROUPNAME	String	Group name
3	ACCOUNT ACCT ACCOUNTNAME	String	Account name
4	CREATOR	String	File creator name
5	SECURITY MATRIX	String	Security matrix for access
-5	SECURITY MATRIX	Integer	Security matrix for access
6	CREATED CREATION DATE FMTCREATED	String	File creation date
-6	CREATION DATE INTEGER INTCREATED	Integer	File creation date
7	ACCESSED FMTACCESSED LAST ACCESS DATE	String	Last access date
-7	LAST ACCESS DATE INTEGER INTACCESSED	Integer	Last access date
8	MODIFIED LAST MOD DATE FMTMODDATE	String	Last modification date
-8	LAST MOD DATE INTEGER INTMODDATE	Integer	Last modification date
9	FILE CODE MNEMONIC FMTFCODE	String	File code of disk file
-9	FCODE INTFCODE	Integer	File code of disk file
10	USER LABELS WRITTEN	Integer	Number of user labels written
11	USER LABELS AVAIL	Integer	Number of user labels available
12	FILE LIMIT LIMIT	Integer	Total number of logical records possible in the file
13	FOPTIONS FMTFOPT	String	File options
-13	FORMATTED FOPTIONS INTFOPT	Integer	File options
14	RECORD SIZE RECSIZE	Integer	Record size
15	BLOCK SIZE BLKSIZE	Integer	Block size
16	MAX EXTENTS MAXEXT	Integer	Maximum number of extents
17	LAST EXTENT SIZE LASTEXTSIZE	Integer	Last extent size
18	EXTENT SIZE EXTSIZE	Integer	Extent size
19	END OF FILE EOF	Integer	Number of logical records in file
20	ALLOC TIME FMTALLOCTIME	String	File allocation time
-20	ALLOC TIME INTEGER INTALLOCTIME	Integer	File allocation time
21	ALLOC DATE FMTALLOCDATE ALLOCATED	String	File allocation date
-21	ALLOC DATE INTEGER INTALLOCDATE	Integer	File allocation date
22	NUM OPEN CLOSE RECS	Integer	Number of open/close records
23	DEVICE NAME DEV NAME	String	Device name (8 bytes
24	FMTMODTIME LAST MOD TIME	String	Last modification time
-24	INTMODTIME LAST MOD TIME	Integer	Last modification time
25	FIRST USER LABEL	String	First user label (user label 0)
27	UNIQUE FILE ID UFID	REC	Unique file identifier (UFID)
28	BYPE FILE SIZE BYTEFILESIZE	Integer	Total number of bytes allowed in file
29	BYTE DATA OFFSET DATASTART	Integer	Start of file offset
30	BYTE RECORD SIZE BYTERECSIZE	Integer	Record size (indicates bytes)
31	BYTE BLOCK SIZE BYTEBLKSIZE	Integer	Block size (indicates bytes)
32	BYTE EXTENT SIZE BYTEEXTSIZE	Integer	Extent size (indicates bytes)
33	LOCKWORD	String	File lockword
34	VOLUME RESTRICTION VOLRESTR	String	Volume restriction
35	VOLUME SET NAME	String	Volume set names
36	LOGSET ID	String	Transaction management log set id
37	LDEV LOGICAL DEVICE NUMBER	Integer	Logical device number
38	POSIX FULL FILE NAME POSIXFULLFNAME	REC	Terminated HFS-syntax system absolute pathname
39	NUM HARD LINKS NUMHARDLINKS	Integer	The current number of hard links to the file
40	ACCESS TIME FMTACCESSTIME LAST ACCESS TIME	String	Time of last file access (clock format)
-40	LAST ACCESS TIME INTEGER INTACCESSTIME	Integer	Time of last file access (clock format)
41	STATUS CHANGE TIME FMTSTATUSCHANGETIME	String	Time of last file status change (clock format)
-41	INTSTATUSCHANGETIME	Integer	Change Time Integer
42	STATUS CHANGE DATE FMTSTATUSCHANGEDATE	String	Date of the last file status change (calendar format)
-42	CHANGE DATE INTEGER INTSTATUSCHANGEDATE	Integer	Date of the last file status change (calendar format)
43	FILE OWNER NAME OWNER	String	File owner
44	FILE OWNER ID UID	Integer	File owner identifier
45	FILE GROUP NAME FILEGROUP	String	File group
46	FILE GROUP ID GID	Integer	File group identifier
47	FILE TYPE FILETYPE	String	File type
-47	FILE TYPE INTEGER INTFILETYPE	Integer	File type
48	RECORD TYPE RECTYPE	Integer	Record type
49	BYTE FILE SIZE BYTEFILESIZE	Integer	Current file size (in bytes)
50	KSAM VERSION KSAMVERS	Integer	KSAM XL file version
51	KSAM LABEL KSAMPARAM	some type by reference	KSAM XL parameters
52	DEVICE TYPE DEVTYPE	String	MPE/iX device type
-52	DEVICE TYPE INTEGER INTDEVTYPE	Integer	MPE/iX device type
53	RELEASED	Boolean	Secured/Released

The FINFO function is often used in file maintenance routines to create, delete, or determine certain characteristics of a file. The following examples demonstrate the responses to several FINFO requests about the file X.PUB.SYS

   :CALC FINFO('X',0)

   TRUE

   :CALC FINFO('X','EXISTS')

   TRUE





   :CALC FINFO('X',13)

   ASCII, FIXED, NOCCTL, STD

   :CALC FINFO('X','FMTFOPT')

   ASCII, FIXED, NOCCTL, STD



   :CALC FINFO('X',1)

   X.PUB.SYS



   :CALC FINFO('X','FULLFNAME')

   X.PUB.SYS



   :CALC FINFO('X',38)

   /SYS/PUB/X

The last example asks for the absolute pathname of the file "X" (HFS syntax). Compare this with the example immediately preceding it, which asks for the file name in MPE syntax.

Comparing Results

The comparison operators, equal (=), less than (<), greater than (>), not equal to (<>), less than or equal to (<=), and equal to or greater than (>=), are provided in the CI expression evaluator. These expressions produce a boolean result that can be used to set the criteria for a conditional branch or a looping structure.