Help categorize the TRS-80 software archive

ZSHELL - by Karl A. Hessinger and Roy Soltoff A feature of the UNIX operating system that has made it famous is the SHELL, a command language interpreter. The 'SHELL' generally provides for the parsing of arguments, the ability of redirecting standard I/O, and pipelines. LDOS already supplies a standard procedure for argument parsing (i.e. @FSPEC, @FEXT, and @PARAM). Now Karl Hessinger has written ZSHELL to supply standard I/O redirection, pipelines, and more. What is standard I/O redirection? Simply this! Your standard input is the KI device. Your standard output is the DO device. LDOS already permits you to redirect all devices by using the ROUTE library command. Under the UNIX 'SHELL' concept, standard I/O redirection permits you to temporarily route either standard input, standard output, or both - for the duration of the execution of a command. The original device linkage is restored AUTOMATICALLY. Programs written to use standard input and output can easily use any device by this temporary redirection - even files! Many commercial programs are written that use the single-key input routine, @KEY or @KBD, to fetch keyboard input. You would just love to be able to run these programs from the sophisticated Job Control Language of LDOS. However, since JCL operates only from the line input routine, @KEYIN, you cannot 'automate' your operation. With ZSHELL, ANY PROGRAM THAT USES THE LDOS KEYBOARD DRIVER CAN BE OPERATED SO THAT ITS INPUT IS FETCHED FROM A DISK FILE. Furthermore, control is automatically passed back to the keyboard when the program's input gathering reaches the end of the 'key' file. This redirection function will pay for the cost of ZSHELL many times by saving you work and time. Piping, under UNIX, operates in a multi-processing environment. One executing program communicates its output to the input of another executing program. The connection is visualized as a 'pipe'. LDOS does not provide multi-processing; however, ZSHELL realizes the pipe as a temporary holding file that receives the output of the first program and uses this file as input to the second. With ZSHELL, you can enter multiple commands on a single line. There is also a provision to designate the PR device as 'standard output' for redirection purposes. With ZSHELL, you will be entering commands such as: LBASIC <TEMP/BAS DIR :1 (A,J,S) LSCRIPT DEVICE (B=N) ; FREE The first example has LBASIC getting its input from the file, TEXT/BAS, reverting to the standard KI linkage upon reaching the end of the file. In the second example, the directory display is automatically loaded into LSCRIPT, while the third illustration is an example of multiple commands on a line. For our LC users, ZSHELL provides a command line over-ride character which if entered, will inhibit ZSHELL from scanning for redirection. Thus, redirection inherent in an LC generated program can be utilized even when ZSHELL is installed and active. ZSHELL is 100X compatible with Job Control Language. JCL job streams can be constructed with commands which use the power of ZSHELL's redirection capabilities. ZSHELL is self relocating and requires less than 1500 bytes of upper memory. It functions only with LDOS 5.1.x versions. It provides I/O redirection of KI [via '<'], DO [via '>'], and optionally, PR [via '>'] in lieu of DO. Standard output can be directed to overwrite or append to [via '>'] a disk file. A program may be piped [via ' '] to another with the pipe file located on the drive of your choice. Multiple commands may be entered on a single line [via ';']. Integrate these UNIX-inspired features into your LDOS and expand your system's capabilities. Included with the ZSHELL package is WC, a wild-card 'shell' processor, written by Roy Soltoff, that allows you to invoke compatible commands on all file specifications that match a wildcardspec entered on the command line. You enter the command once while the WILDCARD shell processor searches the designated disk drive(s) for files that match your wildcard specification. WILDCARD builds a Job Control Language file of your command line substituting each matching file specification for the wildcard specification on a separate command line. WILDCARD then automatically executes the JCL file. The 'wildcardspec' uses the file name and file extension as two distinct fields for matching purposes. If the drive specification is entered, WC will search that specific drive for all files matching the name-extension wildcard fields. If the drive specification is omitted, then all drives will be searched. Within each field, WC accepts two wild characters, '?' and ''. The question mark will match any character in that character position. The asterisk is used to match all trailing characters in the field. For example, '?SHELL/TXT:1 inch will match with ASHELL/TXT, BSHELL/TXT, etc. but ASHELL1/TXT will not match. A global match of all filespecs would be an entry of the form, '/'. whereas a match of all /CMD files would be an entry of the form, '/CMD'. If a minus sign, '-', precedes the filename field, WILDCARD will select files that do not match the wildcardspec. Any entered password will be used in the full file specifications generated by the selection process. WC is quite useful to perform repetitive tasks on files whose file specifications are similarly constructed. For example, to list out all /TXT files on drive 1, you could use a WILDCARD entry of: WC LIST /TXT:1 ORDERING INFORMATION: ZSHELL: For use on the TRS-80 Model I/III/4 under LDOS 5.1.

Appears in Issue 028 of 80 Microcomputing

Article Begins:

Since the early days of the TRS-80, there have been many discoveries about the Model I not documented in the original Level II manual. Short routines, valuable PEEK and POKE addresses and other software tricks have slowly made their way to the TRS-80 user.