C++: Arbitrary File Input

Karim · 03-11-2005, 05:53 PM

I can open a file when the filename is hard coded or if I ask the user and store the filename into a string. But I have no idea how to open a file when the filename is only specified at run-time on the command line. For instance:

myProg filename1
myProg filename2
etc.,

myProg needs to input the text from the various files for processing but I don't know how to get at the contents. This isn't redirection either which I would be fine with.

Any ideas?

CraigSca · 03-11-2005, 05:56 PM

It's been years since I programmed in C, but isn't this part of the main function? Like, argv() and argc()?

gstelmack · 03-11-2005, 06:17 PM

Yup, you need to use the argc and argv parameters to main. argc is the parameter count, and argv is an array of strings that are the command-line parameters tokenized by whitespace.

Karim · 03-11-2005, 07:59 PM

Thanks... something I hadn't seen before.

MikeVic · 03-11-2005, 08:26 PM

I believe array slot 2 has the first command line specified? The first one is the name of the program or something?

gstelmack · 03-11-2005, 09:15 PM

Well, technically it's array slot 1, since C/C++/C# use zero-based indexing ;-)

So if argc == 1, there are no arguments, just the name of the program in argv[0].

03-11-2005, 05:56 PM	#2
CraigSca Pro Starter Join Date: Jul 2001 Location: Not Delaware - hurray!	It's been years since I programmed in C, but isn't this part of the main function? Like, argv() and argc()? __________________ She loves you, yeah, yeah, yeah, yeah! She loves you, yeah! how do you know? how do you know?

03-11-2005, 06:17 PM	#3
gstelmack Pro Starter Join Date: Oct 2000 Location: Cary, NC	Yup, you need to use the argc and argv parameters to main. argc is the parameter count, and argv is an array of strings that are the command-line parameters tokenized by whitespace. __________________ -- Greg -- Author of various FOF utilities

03-11-2005, 09:15 PM	#6
gstelmack Pro Starter Join Date: Oct 2000 Location: Cary, NC	Well, technically it's array slot 1, since C/C++/C# use zero-based indexing ;-) So if argc == 1, there are no arguments, just the name of the program in argv[0]. __________________ -- Greg -- Author of various FOF utilities

03-11-2005, 07:59 PM	#4
Karim College Starter Join Date: Oct 2000 Location: Calgary	Thanks... something I hadn't seen before.

03-11-2005, 08:26 PM	#5
MikeVic Head Coach Join Date: Mar 2003 Location: Hometown of Canada	I believe array slot 2 has the first command line specified? The first one is the name of the program or something?

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