CMS EXEC

The EXEC language

• EXEC processes lines up to 130 characters long when entered from a terminal, or 72 characters when read from a file.
• A label consisting of a dash followed by up to seven alphanumeric characters can prefix a CMS command or an EXEC control statement.
• The interpreter parses commands into blank-delimited tokens of up to eight characters each.
• Variables consist of an ampersand followed by up to seven alphanumeric characters. Variables can be either user-defined variables or pre-defined EXEC variables.
• As each line is read the tokens are scanned. If they contain EXEC variables the variables are replaced by their value.
• Comments. Comments in EXEC files begin with an asterisk in column one. All other statements are executable statements.
• Null statements. A null statement contains no data items.
• CMS commands. If the first data item on a line is not an asterisk or ampersand the EXEC processor considers the line to be a CMS command and passes it to CMS for immediate execution.
• Assignment statements. An assignment statement assigns a value to an EXEC variable. It has the form

  &variable = 

• Control statements. A statement where the first data item is an EXEC control word and the second is not an equals sign is assumed to be a control statement.
• EXEC control words:
• *&ARGS - allows the user to redefine command arguments.
• *&BEGPUNCH - heads a series of lines to be spooled to the user's virtual punch.
• *&BEGSTACK - heads a series of lines to be placed in the user's console input stack.
• *&BEGTYPE - heads a series of lines to be typed on the user's terminal.
• *&END - marks the end of the lines processed by &BEGPUNCH, &BEGSTACK, or &BEGTYPE.
• *&CONTINUE - tells the interpreter to process the next line in the file.
• *&CONTROL - controls the format in which messages are displayed.
• *&ERROR - tells the interpreter what to do if an error is detected.
• *&EXIT - exits the current EXEC file, and optionally sets a return code.
• *&GOTO - branches to another location in the current EXEC file. The location can be TOP for the beginning of the file, a label, or a line number.
• *&IF allows for conditional execution of statements.
• *&LOOP - heads a group of statements to be executed multiple times, or until a specified condition is true.
• *&PUNCH - sends a string of tokens to the user's virtual punch. Each &PUNCH statement generates one card-image, padded or truncated if necessary.
• *&READ - reads one or more lines from the user's terminal.
• *&SKIP - skips a specified number of lines.
• *&SPACE - types a specified number of blank lines on the user's terminal.
• *&STACK - places one line in the user's input stack. The line is constructed from tokens as for &PUNCH.
• *&TIME - specifies what timing information is to be typed on the user's terminal following the execution of each CMS command.
• *&TYPE types a line on the user's terminal. The line is constructed from tokens as for &PUNCH.
• Built-in functions. The EXEC interpreter provides a few "built-in" or predefined functions:
• *&CONCAT concatenates a string of tokens.
• *&DATATYPE examines a token and determines whether it is numeric or alphabetic.
• *&LENGTH returns the length of a token.
• *&LITERAL prevents variable substitution within a token.
• *&SUBSTR extract selected characters from a token.

  Sample code

 The following code issues CMS commands to set
 the "blip" character to asterisk and request
 the "short" format for system ready messages.
&CONTROL OFF
SET BLIP *
SET RDYMSG SMSG

Related CMS Command Procedure Control Languages

• CMS EXEC
• EXEC 2
• REXX