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CMS EXEC
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<h2 id="the-exec-language">The EXEC language</h2> <ul><li>EXEC processes lines up to 130 characters long when entered from a terminal, or 72 characters when read from a file.</li> <li>A <i>label</i> consisting of a <a href="/facts/Hyphen/2qtCxIGv">dash</a> followed by up to seven <a href="/facts/Alphanumeric/ytA9RSIv">alphanumeric</a> characters can prefix a CMS command or an EXEC control statement.</li> <li>The interpreter parses commands into blank-delimited <i><a href="/facts/Token_(parser)/T1JYWpIf">tokens</a></i> of up to eight characters each.</li> <li>Variables consist of an <a href="/facts/Ampersand/emmXUXuB">ampersand</a> followed by up to seven alphanumeric characters. Variables can be either user-defined variables or pre-defined ("special") EXEC variables.</li> <li>As each line is read the tokens are scanned. If they contain EXEC variables the variables are replaced by their value.</li> <li>Comments. Comments in EXEC files begin with an <a href="/facts/Asterisk/qwmtPW5V">asterisk</a> in column one. All other statements are executable statements.</li> <li>Null statements. A null statement contains no data items.</li> <li>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.</li> <li>Assignment statements. An assignment statement assigns a value to an EXEC variable. It has the form &variable = <arithmetic-expression></li> <li>Control statements. A statement where the first data item is an <i>EXEC control word</i> and the second is not an <a href="/facts/Equals_sign/AweYSg9h">equals sign</a> is assumed to be a control statement.</li> <li>EXEC control words: <ul><li>&ARGS - allows the user to redefine command arguments.</li> <li>&BEGPUNCH - heads a series of lines to be spooled to the user's virtual punch.</li> <li>&BEGSTACK - heads a series of lines to be placed in the user's console input stack.</li> <li>&BEGTYPE - heads a series of lines to be typed on the user's terminal.</li> <li>&END - marks the end of the lines processed by &BEGPUNCH, &BEGSTACK, or &BEGTYPE.</li> <li>&CONTINUE - tells the interpreter to process the next line in the file.</li> <li>&CONTROL - controls the format in which messages are displayed.</li> <li>&ERROR - tells the interpreter what to do if an error is detected.</li> <li>&EXIT - exits the current EXEC file, and optionally sets a return code.</li> <li>&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.</li> <li>&IF allows for conditional execution of statements.</li> <li>&LOOP - heads a group of statements to be executed multiple times, or until a specified condition is true.</li> <li>&PUNCH - sends a string of tokens to the user's virtual punch. Each &PUNCH statement generates one card-image, padded or truncated if necessary.</li> <li>&READ - reads one or more lines from the user's <a href="/facts/Computer_terminal/fSlx05qV">terminal</a>.</li> <li>&SKIP - skips (ignores) a specified number of lines.</li> <li>&SPACE - types a specified number of blank lines on the user's terminal.</li> <li>&STACK - places one line in the user's input stack. The line is constructed from tokens as for &PUNCH.</li> <li>&TIME - specifies what timing information is to be typed on the user's terminal following the execution of each CMS command.</li> <li>&TYPE types a line on the user's terminal. The line is constructed from tokens as for &PUNCH.</li></ul></li> <li>Built-in functions. The EXEC interpreter provides a few "built-in" or predefined functions: <ul><li>&CONCAT concatenates a string of tokens.</li> <li>&DATATYPE examines a token and determines whether it is numeric or alphabetic.</li> <li>&LENGTH returns the length of a token.</li> <li>&LITERAL prevents variable substitution within a token.</li> <li>&SUBSTR extract selected characters from a token.</li></ul></li></ul> <h2 id="sample-code">Sample code</h2> <p><i>PROFILE EXEC</i> is an EXEC that is automatically executed when a user logs on to tailor their environment. A simple PROFILE EXEC might look like the following: </p> * 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 <h2 id="related-cms-command-procedure-control-languages">Related CMS Command Procedure Control Languages</h2> <ul><li>CMS EXEC</li> <li><a href="/facts/EXEC_2/GfVWNLu3">EXEC 2</a></li> <li><a href="/facts/REXX/hAzh6FeR">REXX</a></li></ul> <h2 id="external-links">External links</h2> <ul><li>"The CMS EXEC Processor". <a href="https://archive.today/20140417183004/http://publibfp.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/HCSD7B00/CCONTENTS#5.1"><i>CMS User's Guide</i></a> (1st ed.). September 2004. IBM publication number SC24-6079-00. Archived from <a href="http://publibfp.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/HCSD7B00/CCONTENTS#5.1">the original</a> on April 17, 2014.</li> <li><a href="https://web.archive.org/web/20090221183151/http://www-01.ibm.com/software/awdtools/rexx/library/share56.html">"REX - A Command Programming Language"</a>. <i>Share 56</i>. February 18, 1981. Archived from <a href="http://www.ibm.com/software/awdtools/rexx/library/share56.html">the original</a> on 2009-02-21.</li> <li><a href="https://web.archive.org/web/20110814143648/http://www.bitsavers.org/pdf/ibm/370/vm370/GC20-1812-1_VM370exec_Apr75.pdf"><i>IBM Virtual Machine Facility/370: EXEC User's Guide</i></a> (PDF) (2nd ed.). April 1975. IBM publication number GC20-1812-1. Archived from <a href="http://www.bitsavers.org/pdf/ibm/370/vm370/GC20-1812-1_VM370exec_Apr75.pdf">the original</a> (PDF) on 2011-08-14. Retrieved 2012-03-14.</li></ul> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>Varian, Melinda. "VM AND THE VM COMMUNITY: Past, Present, and Future" (PDF). Retrieved Mar 9, 2012. <a href="http://web.me.com/melinda.varian/Site/Melinda_Varians_Home_Page_files/neuvm.pdf" target="_blank">http://web.me.com/melinda.varian/Site/Melinda_Varians_Home_Page_files/neuvm.pdf</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> </ol>