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From: madd@bucsb.bu.edu.UUCP (Jim "Jack" Frost)
Newsgroups: comp.lang.pascal,comp.sys.ibm.pc
Subject: Re: Environment variables in Turbo Pascal
Message-ID: <1078@bucsb.bu.edu.UUCP>
Date: Sat, 1-Aug-87 20:54:14 EDT
Article-I.D.: bucsb.1078
Posted: Sat Aug  1 20:54:14 1987
Date-Received: Sun, 2-Aug-87 10:47:06 EDT
References: <151@ivory.SanDiego.NCR.COM>
Reply-To: madd@bucsb.bu.edu.UUCP (Jim "Jack" Frost)
Distribution: world
Organization: ODO (Organization for the Disorganization of Organization)
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Xref: mnetor comp.lang.pascal:228 comp.sys.ibm.pc:6255

In article <151@ivory.SanDiego.NCR.COM> mike@ivory.UUCP (Michael Lodman) writes:
>Could someone please email and tell me how to read the DOS environment
>variables with Turbo Pascal?
>
>Thanks.

This is easy.  Note that MS-DOS gives you a pointer to the environment
variable list at memw[cseg:$2C].  This simple program will print out
the environment; I suspect that anyone with a little knowledge can
expand it to a complete getenv() style function in just a few minutes.

[note -- I am just making this up now.  no flames if I screw it up a
little]

program printenv;
var eseg,           { segment of environment }
    p    : integer; { pointer within segment }
begin
  eseg:= memw[cseg:$2C];           { get pointer to env segment }
  p:= 0;                           { initialize pointer within segment }
  repeat                           { loop for all environment entries }
    while mem[eseg:p]<>0 do begin  { loop for chars in each entry }
      write(chr(mem[eseg:p]));     { display character in entry }
      p:= p+1                      { go to next character in entry }
    end;                           { end environment enty loop }
    writeln;                       { next line for next entry }
    p:= p+1                        { go to next environment entry }
  until mem[eseg:p]=0              { environment ends in a null byte }
end.

For those of you who don't know, MS-DOS defines the environment as a
series of null-terminated strings that ends in a null.  This means
that each entry in the environment ends in a null (chr(0), #0,
whatever), and the last entry has another null following the null of
the last string.  Pretty easy to program with that info and the
address of the segment!

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          Jim Frost * The Madd Hacker | UUCP: ..!harvard!bu-cs!bucsb!madd
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