" -*-fundamental-*- " sh -- a shell " started by p budne 3/4/2016 " with code from cat.s, init.s, and looking at the v1 (pdp-11) shell " BUG: XXX second char of second word being incremented????? start: " XXX take command line argument (script file to open), suppress prompt?? " NOTE!!! v0 init.s doesn't set up the argv at the top of memory, " so the v0 shell may not have taken command line arguments!!! " if non-interactive, "dzm prompt", jump to newcom interactive: -1 sys intrp " make shell uninterruptable sys getuid sma " <0? jmp newline " no, a mundane lac hash " yes: superuser dac prompt " change prompt newline: lac d1; sys write; prompt; 1 " output prompt newcom: dzm argc " clear arg count dzm char " clear saved char dzm infile " clear input redirect file name dzm outfile " clear output redirect file name lac iopt " reset output pointer dac opt dac nextarg newarg: -8 " save 8 chars dac bcount dzm redirect lac opt " save start for print (TEMP) dac 8f dac nextarg jms blank " skip whitespace sad o12 " newline? jmp eol " yes sad lt " input redirect? jmp redirin sad gt " output redirect? jmp redirout jmp 3f redirin: " saw < dac redirect " flag redirect lac infilep dac opt dac 8f " TEMP jmp newchar " v1 behavior? no whitespace eater redirout: " saw > dac redirect " flag redirect lac outfilep dac opt dac 8f " TEMP " v1 behavior? no whitespace eater " fall newchar: jms getc sad o40 " space? jmp ws " yes sad o12 jmp ws 3: jms putc " save isz bcount " loop unless full jmp newchar " here after 8 chars: discard until terminator seen discard: jms getc dac char sad o4 jmp eof sad o12 jmp eoname sad o40 jmp eoname jmp discard " here with EOF in command eof: sys exit " quit, for now? " name ended (short) with whitespace or newline " pad out last name to 8 with spaces ws: dac char 1: lac o40 jms putc " no: copy into argv isz bcount " loop until full jmp 1b " saw end of name eoname: lac redirect sza jmp 1f " last name was a redirect file, skip increment isz argc " increment argc lac nextarg tad d4 " advance nextarg dac nextarg 1f: " TEMP output each name on a line: lac d1; sys write; 8:0; 4 lac d1; sys write; nl; 1 lac nextarg dac opt dac 8b " TEMP lac char sad o12 jmp eol -maxargs tad argc sza jmp newarg " here at end of line (or too many args) eol: " XXX check for "chdir", execute "in-process" " XXX if not, fork (child code below) " XXX parent wait for child (unless &) jmp newline child: cla sad infile jmp 1f sys close " close fd 0 sys open; infile; 0 " open redirected spa jmp inerror cla " XXX should still be zero! 1: sad outfile jmp 1f lac d1 sys close " close fd 1 " XXXXXXXXXX use creat!!!? sys open; outfile; 1 " open redirected spa jmp outerror " here to exec filename at argv, code adapted from init.s " right now always look in "system" directory. " but on error, check local directory? 1: sys unlink; exectemp sys link; system; argv0; exectemp spa jmp nofile sys open; exectemp; 0 spa jmp error sys unlink; exectemp jmp 1f nofile: " not found in "system" sys open; argv0; 0 " try cwd spa jmp cmderr 1: law bootloc-1 " Copy the code at the boot label below dac 9 " up to high memory law boot-1 dac 8 1: lac 8 i dac 9 i sza " Stop copying when we hit the 0 marker jmp 1b jmp bootloc " and then jump to the code boot: lac d2 " Load fd2 (the opened shell file) lmq " Save the fd into MQ sys read; userbase; userlen " read executable in lacq " Get the fd back and close the file sys close jmp userbase " and jump to the beginning of the executable 0 " 0 marks the end of the code, used by the copy loop bootlen=.-boot " length of bootstrap inerror: law infile jmp error outerror: law outfile skp cmderr: law argv0 error: " here for error in child dac 1f lac d1 " XXX stdout may be redirected!!!! sys write qmsp; 1 lac d1 sys write; 1: 0; 4 lac d1 sys write; nl; 1 " XXX smes to shell??? sys exit " end code from init.s " ================ blank: 0 1: jms getc sad o40 jmp 1b jmp blank i " give skip return if AC *NOT* a command delimiter delim: 0 sad o12 jmp delim i isz delim jmp delim i " **************************************************************** " from cat.s getc: 0 lac ipt " Load the pointer to the next word in the buffer sad eipt jmp 1f " We've reached the end of the buffer, so read more dac 2f " Save the pointer add o400000 " Flip the msb and save into ipt dac ipt ral " Move the msb into the link register lac 2f i " Load the word from the buffer szl " Skip if this is the second character in the word lrss 9 " It's the first char, shift down the top character and o177 " Keep the lowest 7 bits sna jmp getc+1 " Skip a NUL characters and read another one jmp getc i " Return the character from the subroutine 1: cla " Buffer is empty, read another 64 characters sys read; ibuf; 64 sna jmp 1f " No characters were read in tad iipt " Add the word count to the base of the buffer dac eipt " and store in the end buffer pointer lac iipt " Reset the ipt to the base of the buffer dac ipt jmp getc+1 " and loop back to get one character 1: lac o4 " No character, return with ctrl-D jmp getc i " return from subroutine putc: 0 and o177 " Keep the lowest 7 bits and save into 2f+1 dac 2f+1 lac opt " Save the pointer to the empty buffer dac 2f " position to 2f add o400000 " Flip the msb and save back into opt dac opt " This also has the effect of incrementing " the opt pointer every second addition! spa " If the bit was set, we already have one jmp 1f " character at 2f+1. If no previous character, lac 2f i " merge the old and new character together xor 2f+1 jmp 3f " and go to the "save it in buffer" code 1: lac 2f+1 " Move the character up into the top half alss 9 3: dac 2f i " Save the word into the buffer jmp putc i " No, so return (more room still in the buffer) 2: 0;0 " Current input and output word pointers ipt: 0 " Current input buffer base eipt: 0 " Pointer to end of data read in input buffer iipt: ibuf ibuf: .=.+64 " end from cat.s " **************************************************************** " constants d1: 1 d2: 2 o4:d4: 4 o12:nl: 012 " newline o40:sp: 040 " space o74:lt: 074 o76:gt: 076 o177: 0177 " ASCII mask o400000: 0400000 " Msb toggle bit hash: <#> " superuser prompt qmsp: " system: ;;; 040040 exectemp: ;; " temporary link for file being exec'ed " TEMP FOR DEBUG: star: <*> " " ################ variables prompt: <@> " v1 prompt pid: 0 " "other" pid char: 0 " white space char redirect: 0 " last file was a redirect (lt or gt) bcount: 0 " byte counter for current filename iopt: argc-4 " initial value for nextarg, opt nextarg: 0 " next slot in argv to fill opt: 0 " "output pointer" (may point to in/outfile) infilep: infile outfilep: outfile outfile: .=.+4 " buffer for output redirect file name infile: .=.+4 " buffer for input redirect file name " == high memory userbase=010000 userlen=userbase-bootloc " max executable argptr=017777 " last word points to argc + argv data " leave room for maxargs items of 4 words each maxargs=8 argc=argptr-maxargs-maxargs-maxargs-maxargs " 4 word blocks follow argc: argv0=argc+1 " "bootstrap" (reads executable into userbase) below argc: bootloc=argc-bootlen " location of bootstrap