DOS ain't dead - Where is paramstr(0) hide ?

DosWorld

25.12.2020, 22:39

Where is paramstr(0) hide ? (Developers)

Hello!

Does any anybody know, where is DOS have path and name of executed program?
I talk about paramstr(0) (in pascal) or first element of argv (in C) - like C:\PATH\COOLPRG.EXE

I am try disassemble minimal program in TP7, but have 31k disassembled text :-) and continue investigate (may be somebody already known it and can make may path is short).

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Make DOS great again!

Carthago delenda est, Ceterum censeo Carthaginem delendam esse.

ecm

Düsseldorf, Germany,
25.12.2020, 22:51

@ DosWorld

Where is paramstr(0) hide ?

Post reply

> Hello!
>
> Does any anybody know, where is DOS have path and name of executed
> program?
> I talk about paramstr(0) (in pascal) or first element of argv (in C) - like
> C:\PATH\COOLPRG.EXE
>
> I am try disassemble minimal program in TP7, but have 31k disassembled text
> :-) and continue investigate (may be somebody already known it and can make
> may path is short).

I believe it is at the end of the environment block, after the double-zero that marks the end of the variables stored in the block.

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l

Laaca

Czech republic,
26.12.2020, 00:10

@ ecm

Where is paramstr(0) hide ?

Post reply

It is in PSP (program segment prefix)
Look at wikipedia article: https://en.wikipedia.org/wiki/Program_Segment_Prefix

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DOS-u-akbar!

tkchia

26.12.2020, 07:22

@ ecm

Where is paramstr(0) hide ?

Post reply

Hello ecm,

> I believe it is at the end of the environment block, after the double-zero
> that marks the end of the variables stored in the block.

Indeed --- according to the all-knowing RBIL: :-D
Format of environment block: Offset Size Description (Table 01379) 00h N BYTEs first environment variable, ASCIZ string of form "var=value" N BYTEs second environment variable, ASCIZ string ... N BYTEs last environment variable, ASCIZ string of form "var=value" BYTE 00h ---DOS 3.0+ --- WORD number of strings following environment (normally 1) N BYTEs ASCIZ full pathname of program owning this environment other strings may follow
(This is under the entry for int 0x21, ah = 0x26.)

I wonder if there is a way to get the program name for DOS versions before 3.0.

Thank you!

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https://gitlab.com/tkchia · https://codeberg.org/tkchia · 😴 "MOV AX,0D500H+CMOS_REG_D+NMI"

DosWorld

29.12.2020, 00:41

@ ecm

Where is paramstr(0) hide ?

Post reply

> I believe it is at the end of the environment block, after the double-zero
> that marks the end of the variables stored in the block.

Thanks! It works!

---
Make DOS great again!

Carthago delenda est, Ceterum censeo Carthaginem delendam esse.