Passing args to C programs

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2 total messages Started by Ben Aveling Thu, 01 Oct 1992 23:43

#153

Author: Ben Aveling
Date: Thu, 01 Oct 1992 23:43

8 lines
656 bytes

This may be the wrong place, but can someone please
tell me, how can I pass command-line arguments to
a C program.  I know how to do it in Unix, or Ultrix,
but not VMS.

Thanks in anticipation

Ben

Re: Passing args to C programs

#156

Author: Terry Poot
Date: Fri, 02 Oct 1992 14:19

46 lines
2209 bytes

In the C code, everything is the same. However, you have to define a foreign
command symbol for your program. For instance, if your executable is
dua0:[foo]test.exe, enter

foo :== $dua0:[foo]test.exe

You can then run your program as:

foo arg1 arg2

and the command line arguments will be passed through argc and argv as usual.

A few notes:

1) Note the "$" at the beginning of the file spec, it's required. Also, the
filespec will default to looking in sys$system for the executable so be sure to
use a fully qualified file name (i.e. include the device and directory or some
logical name that points to the device and directory.

2) DCL normally forces all unquoted arguments to upper case. The C run-time
library counters this by forcing them all to lower case. If you want an argument
to be passed in upper or mixed case, you have to quote it, as in:

foo "-AaBb" arg1 Arg2 ARG3 "Arg4"

In the above, the options string and Arg4 will get through in mixed case, args
1-3 will all be lower case. And don't try the short cut of quoting all the args
with one set of quotes, because that will make the whole quoted string one
argument.

3) argv[0] is NOT the command typed to run the program, it is the whole fully
qualified file name. This can mess up the way most unix programs print their
error messages. Of course, your program can do something like:

#ifdef VMS
argv[0] = "foo"
#endif

to get around this.

Obtw, yes this is the right group for this type of question.
--
Terry Poot <tp@mccall.com>                   The McCall Pattern Company
(uucp: ...!rutgers!depot!mccall!tp)          615 McCall Road
(800)255-2762, in KS (913)776-4041           Manhattan, KS 66502, USA

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