mirror of
https://github.com/DoctorWkt/pdp7-unix.git
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451 lines
11 KiB
Plaintext
451 lines
11 KiB
Plaintext
" -*-fundamental-*-
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" pbsh -- a shell
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" started by p budne 3/4/2016
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" with code from init.s, cat.s and looking at the v1 (pdp-11) shell
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" In particular, the newline/newcom/newarg/newchar processing loop(s)
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" are copied from the v1 shell:
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" redirection must occur at the start of a name (after whitespace)
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" includes ';' and '&' (unknown if available in v0 shell)
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" does NOT (yet) include quoting (backslash or single quote)
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" no "globbing" (performed by /etc/glob in v1 shell)
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" v0 cat.s seems to write error output on fd 8, *BUT* shell doesn't
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" know what device is on stdout (passed by init, and init doesn't pass
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" fd 8), and there isn't a "dup" call, nor does init appear to be an
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" "indirect" device like /dev/tty, nor does init make an equivalent link!!
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" Arguments for new processes are located at the end of memory.
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" Location 17777 points to a word with the argument count (argc),
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" followed by blocks of four words with (filename) arguments.
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" Currently leave room for ONLY maxargs items.
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maxargs=8
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" v1 shell expects "-" as argument from init or login, will read
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" filename passed as argument. *BUT* v0 init.s doesn't set up the
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" argv at the top of memory, so the v0 shell may not have taken
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" command line arguments!!!
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lac d1
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sys intrp " make shell uninterruptable
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sys getuid
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sma " <0?
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jmp newline " no
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lac hash " yes: superuser
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dac prompt " change prompt
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newline:
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lac d1; sys write; prompt; 1 " output prompt
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jms rline " read line into ibuf
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lac iipt
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dac ipt
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newcom:
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dzm char " clear saved char
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dzm infile " clear input redirect file name
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dzm outfile " clear output redirect file name
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lac iopt " reset output buffer pointer
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dac opt
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dac nextarg
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" reset high memory
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dzm argc " clear arg count
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lac argcptr " (re) set arg pointer
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dac argptr
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dzm argv0 " clear out argv0 for chdir comparison
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dzm argv0+1
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dzm argv0+2
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" NOTE! behavior copied from v1 shell!!!
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" "improvements" here may be non-historic!!
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newarg:
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-8 " save 8 chars
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dac bcount
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dzm redirect " clear redirect flag
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lac opt " save start for print (TEMP)
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dac nextarg
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jms blank " skip whitespace
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jms delim " command sep?
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jmp eol " yes
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sad lt " input redirect?
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jmp redirin
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sad gt " output redirect?
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jmp redirout
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jmp 3f
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redirin: " saw <
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dac redirect " flag redirect
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lac infilep
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dac opt
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jmp newchar
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redirout: " saw >
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dac redirect " flag redirect
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lac outfilep
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dac opt
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" fall
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newchar:
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jms getc
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sad o40 " space?
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jmp eoname " yes
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jms delim
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jmp eoname
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3: jms putc " save
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isz bcount " loop unless full
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jmp newchar
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" here after 8 chars: discard until terminator seen
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discard:
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jms getc
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jms delim " end of line?
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jmp eoname
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sad o40
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jmp eoname
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jmp discard
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" name ended (short) with whitespace or delim
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" pad out last name to 8 with spaces
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" XXX check if ANYTHING read
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eoname:
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dac char " save terminator
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1: lac o40
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jms putc " no: copy into argv
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isz bcount " loop until full
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jmp 1b
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" saw end of name
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2: lac redirect
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sza
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jmp 2f " last name was a redirect file, skip increment
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lac argc " increment argc
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tad d4
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dac argc
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lac nextarg
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tad d4 " advance nextarg
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dac nextarg
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2:
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dzm redirect " clear redirect flag
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lac nextarg
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dac opt
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lac char
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jms delim
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jmp eol
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lac argc
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sad maxargwords
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skp
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jmp newarg
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" too many args, (complain?). for now eat rest of line
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4: jms getc
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jms delim
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skp
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jmp 4b
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lac d1; sys write; toomany; ltoomany
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jmp newline
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" here at end of line
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eol:
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sad delimchar " save eol character
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lac argc " check for empty command line
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sna " get anything?
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jmp 2f " no, go back for another
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" check for built-in "chdir" command
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lac argv0
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sad chdirstr
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skp
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jmp 1f
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lac argv0+1
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sad chdirstr+1
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skp
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jmp 1f
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lac argv0+2
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sad chdirstr+2
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jmp changedir
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1:
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" comment these out to test "exec" w/o fork
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sys fork
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jmp parent
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sys open; argv0; 0 " try cwd (no link required)
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sma
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jmp 1f
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" jmp cmderr
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sys unlink; exectemp " remove old temp file, if any
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sys link; system; argv0; exectemp
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spa
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jmp cmderr
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sys open; exectemp; 0
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spa
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jmp cmderr
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dac cmdfd
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sys unlink; exectemp
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skp
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1: dac cmdfd " save command file descriptor
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cla " check for input redirection
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sad infile " input redirct?
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jmp 1f " no
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sys close " close fd 0
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sys open; infile; 0 " open redirected
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spa sna
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jmp inerror
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cla
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1: sad outfile " output redirec?
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jmp exec " no
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lac d1; sys close " close fd 1
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lac o17; sys creat; outfile " open output redirect
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spa
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jmp outerror
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" here to "exec" file open on cmdfd, adapted from init.s
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exec:
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law boot-1 " Get source addr
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dac 8 " set up index (pre-increments)
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law bootloc-1 " Copy "boot" code into high memory
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dac 9 " set up index
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-bootlen " isz loop count for bootstrap copy
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dac bootcount
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1: lac 8 i
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dac 9 i
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isz bootcount " can only do this once!
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jmp 1b
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lac cmdfd " get fd for the executable
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lmq " Save the fd into MQ
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jmp bootloc " and then jump to the code
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" copied up to bootloc in high memory (below argc)
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boot:
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sys read; userbase; userlen " read executable in
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lacq " Get the fd back and close the file
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sys close " close command file
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jmp userbase " and jump to the beginning of the executable
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bootlen=.-boot " length of bootstrap
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" error in child process:
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inerror: " error opening input redirection
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lac infilep
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jmp error
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outerror: " error opening new stdout (stdout closed!)
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lac outfilep
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skp
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cmderr: " error opening command
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lac argv0p
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error: " error in child: filename pointer in AC
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dac 1f " save filename to complain about
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lac d1; sys write; 1: 0; 4
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lac d1; sys write; qmnl; 1
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lac d2; sys close " close executable, if any
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sys exit
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" chdir command: executed in shell process
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changedir:
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" XXX check if argc == 4 (no directories) and complain??
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lac argv0p
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skp
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1: lac 0f " increment argvp
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tad d4
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dac 0f
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-4 " decrement argc
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tad argc
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dac argc
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sna " done?
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jmp 2f " yes: join parent code
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sys chdir; 0:0
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sma " error?
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jmp 1b " no: look for another directory
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" chdir call failed
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lac 0b
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dac 0f
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lac d1; sys write; 0:0; 4
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lac d1; sys write; qmnl; 1
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jmp 2f " join parent code
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" here in parent, child pid in AC
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parent:
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" https://www.bell-labs.com/usr/dmr/www/hist.html
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" The message facility was used as follows: the parent shell, after
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" creating a process to execute a command, sent a message to the new
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" process by smes; when the command terminated (assuming it did not
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" try to read any messages) the shell's blocked smes call returned an
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" error indication that the target process did not exist. Thus the
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" shell's smes became, in effect, the equivalent of wait.
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"
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" PLB: The "exit" system call code apears to "fall" into the
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" rmes code So Dennis' memory of what the shell did may have
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" been correct, but not for the reason he remembered.
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dac pid " save child pid
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lac delimchar " get command delimiter
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sad o46 " ampersand?
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jmp newcom " yes: go back without wait
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lac pid " no: get pid
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sys smes " hang until child exits
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2: lac delimchar
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sad o73 " semi?
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jmp newcom " yes: look for another command w/o prompt
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jmp newline " no: output prompt
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" ================
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" subroutines
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" eat spaces
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" v1 routine name:
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blank: 0
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1: jms getc
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sad o40
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jmp 1b
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jmp blank i
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" give skip return if AC *NOT* a command delimiter
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" v1 routine name:
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delim: 0
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sad o12 " newline
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jmp delim i
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sad o46 " ampersand
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jmp delim i
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sad o73 " semi
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jmp delim i
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isz delim " ran the gauntlet: skip home
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jmp delim i
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" get character from ibuf
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getc: 0
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lac ipt i " fetch char
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isz ipt " increment pointer
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jmp getc i
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" from init.s rline: read line from tty into ibuf
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" (store one character per word)
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rline: 0
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law ibuf-1 " Store ibuf pointer in location 8
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dac 8
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1:
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cla; sys read; char; 1 " Read in one character from stdin
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sna " read ok?
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sys exit " EOF: quit
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lac char
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lrss 9 " Get it and shift down 9 bits
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sad o100 " '@' (kill) character?
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jmp rline+1 " yes: start from scratch
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sad o43 " '#' (erase) character?
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jmp 2f " yes: handle below
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dac 8 i " Store the character in the buffer
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sad o12 " Newline?
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jmp rline i " yes: return
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jmp 1b " no: keep going
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2:
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law ibuf-1 " # handling. Do nothing if at start of the buffer
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sad 8
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jmp 1b " and loop back
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-1
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tad 8 " Otherwise, move the pointer in location 8 back one
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dac 8
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jmp 1b " and loop back
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putc: 0
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and o177 " Keep the lowest 7 bits and save into 2f+1
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dac 2f+1
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lac opt " get output buffer pos
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dac 2f " save
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add o400000 " Flip the msb (advance) and save back into opt
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dac opt
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spa " If the bit was set, we already have one
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jmp 1f " character at 2f+1. If no previous character,
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lac 2f i " merge the old and new character together
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xor 2f+1
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jmp 3f " and go to the "save it in buffer" code
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1:
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lac 2f+1 " Move the character up into the top half
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alss 9
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3:
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dac 2f i " Save the word into the buffer
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jmp putc i " No, so return (more room still in the buffer)
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2: 0;0 " pointer, char
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" literals
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d1: 1
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d2: 2
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o4:d4: 4
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o12: 012 " newline
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o17: 017
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o40: 040 " space
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o43: 043 " #
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o46: 046 " ampersand
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o73: 046 " semi
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o74:lt: 074 " <
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o76:gt: 076 " >
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o100: 0100 " @
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o177: 0177 " 7-bit (ASCII) mask
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o400000: 0400000 " MSB
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hash: <#> " superuser prompt
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qmnl: <? 012 " question mark, newline
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system:
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<sy>;<st>;<em>; 040040
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exectemp:
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<ex>;<ec>;<te>;<mp> " temporary link for file being exec'ed
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chdirstr:
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<ch>;<di>;<r 040
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" TEMP FOR DEBUG:
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star: <*> "
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toomany: <to>;<o> ;<ma>;<ny>;< a>;<rg>;<s 012
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ltoomany=.-toomany
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maxargwords: maxargs+maxargs+maxargs+maxargs
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argcptr: argc
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infilep: infile
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outfilep: outfile
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iipt: ibuf
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iopt:argv0p: argv0 " initial value for nextarg, opt
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" ################ variables
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prompt: <@ 040 " v1 prompt!
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redirect: .=.+1 " last file was a redirect (lt or gt)
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nextarg: .=.+1 " next slot in argv to fill
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bcount: .=.+1 " byte counter for current filename
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opt: .=.+1 " "output pointer" (may point to in/outfile or into argv)
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delimchar: .=.+1 " character that terminated line
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char: .=.+1 " char that terminated word
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outfile: .=.+4 " buffer for output redirect file name
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infile: .=.+4 " buffer for input redirect file name
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pid: .=.+1 " "other" pid
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cmdfd: .=.+1 " fd for executable
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bootcount: .=.+1 " loop count for "boot" copy
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ipt: .=.+1 " input buf pointer
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ibuf: " input line stored here, one character per word
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userbase=010000 " user starts at 4K
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argptr=017777 " last word points to argc + argv data
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argc=argptr-maxargs-maxargs-maxargs-maxargs-1 " argc followed by argv
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" arguments in 4 word blocks follow argc
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argv0=argc+1
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" "bootstrap" (reads executable into userbase) JUST below argc
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bootloc=argc-bootlen " location of bootstrap
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userlen=bootloc-userbase " max executable
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