File I/O in c++ and linux command line redirect

Question

I've got a program that accepts a text file with a map on it, then finds the shortest path and outputs that to another file.

it needs to work like this

./pathFinder -arg < inputMap.txt > outputMap.txt

My question is, with this input, what would get filled into argv[] and argc (do the redirects count as arguments), and also should I use file streams or just cin/cout... or maybe something else. Thanks.

I just tried using cin and the program waits for input instead of using the txt file. — Max
– Max, Commented Sep 22, 2011 at 1:03
@Max - if your program waits for input, then either you aren't invoking as you describe, or your program has a bug. Please reduce your program to the smallest version that still exhibits the problem, and post that here. For comparison, see this program. — Robᵩ
– Robᵩ, Commented Sep 22, 2011 at 1:56

Oliver Charlesworth · Accepted Answer · 2011-09-22 01:06:06Z

3

argc will be 2, and argv[1] will point to "-arg".

Redirects will simply appear on stdin and stdout (wrapped by std::cin and std::cout).

answered Sep 22, 2011 at 1:06

Oliver Charlesworth

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7 Comments

Oliver Charlesworth Over a year ago

@quasiverse: No. This is handled by the shell.

Max Over a year ago

cin>>var hangs for keyboard input, is there a different way if you are expecting input from a file?

Oliver Charlesworth Over a year ago

@Max: I'm not sure I understand what you mean. The shell literally streams in the content of the file instead of the characters you type at the console.

flight Over a year ago

@Max If you redirect it and it still hangs then the file doesn't have the correct input or you're doing it wrong.

Max Over a year ago

Thanks for the help thus far... When I run the program, it behaves the same way whether I include the redirects or not. (waits for input)

|

Gabe · Accepted Answer · 2011-09-22 01:21:18Z

2

argv will contain {"./pathFinder", "-arg"}

edited Sep 22, 2011 at 1:21

answered Sep 22, 2011 at 1:07

Gabe

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1 Comment

Gabe Over a year ago

@Kerrek: Thanks. I should have just used copy/paste.

John Yang · Accepted Answer · 2011-09-22 01:13:21Z

0

The redirect will not count as arguments. Just use cin/cout will be fine.

answered Sep 22, 2011 at 1:13

John Yang

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